JP2005049899A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device which has a wide viewing angle and high display quality and performs bright display. <P>SOLUTION: The liquid crystal display device has picture element electrodes which are disposed for each picture element region on the liquid crystal layer side of a 1st substrate, and a counter electrode arranged on a 2nd substrate and faced to the picture element electrodes via the liquid crystal layer. In each picture element region, the picture element electrode has a solid part including a plurality of unit solid parts. The liquid crystal layer is brought into a vertical alignment state when no voltage is applied, and a plurality of liquid crystal domains each in a radially-inclined alignment state are formed in the regions corresponding to the unit solid parts by a bias electric field generated on the peripheries of the unit solid parts when voltage is applied. The liquid crystal display device is further provided with auxiliary capacitors connected electrically parallel to liquid crystal capacitors and at least portions of the auxiliary capacitors is located within the regions of the lst substrate not provided with the solid parts. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device having a wide viewing angle characteristic and performing high-quality display.

  In recent years, a thin and light liquid crystal display device has been used as a display device used for a display of a personal computer or a display unit of a portable information terminal device. However, the conventional twisted nematic type (TN type) and super twisted nematic type (STN type) liquid crystal display devices have a drawback that the viewing angle is narrow, and various technical developments have been made to solve this. ing.

  As a typical technique for improving the viewing angle characteristics of a TN type or STN type liquid crystal display device, there is a method of adding an optical compensation plate. As another method, there is a lateral electric field method in which an electric field in a horizontal direction is applied to the liquid crystal layer with respect to the surface of the substrate. This horizontal electric field type liquid crystal display device has recently been mass-produced and has attracted attention. As another technique, there is DAP (deformation of vertical aligned phase) using a nematic liquid crystal material having negative dielectric anisotropy as a liquid crystal material and using a vertical alignment film as an alignment film. This is one of voltage controlled birefringence (ECB) method, and the transmittance is controlled by utilizing the birefringence of liquid crystal molecules.

  However, although the horizontal electric field method is one of the effective methods for widening the viewing angle, the production margin is significantly narrower in the manufacturing process compared to the normal TN type, so that stable production is difficult. is there. This is because unevenness in the gap between the substrates and deviation in the transmission axis (polarization axis) direction of the polarizing plate with respect to the alignment axis of the liquid crystal molecules greatly affect the display brightness and contrast ratio. In order to achieve stable production, further technological development is necessary.

  In addition, in order to perform uniform display without display unevenness in a DAP liquid crystal display device, it is necessary to perform alignment control. As a method for controlling the alignment, there is a method of performing an alignment treatment by rubbing the surface of the alignment film. However, when the rubbing treatment is performed on the vertical alignment film, rubbing streaks are likely to occur in the display image, which is not suitable for mass production.

Therefore, the inventor forms a predetermined electrode structure including an opening and a solid part on one of a pair of electrodes facing each other through the liquid crystal layer together with others, and is generated at the edge of the opening. A method has been proposed in which a plurality of liquid crystal domains having radially inclined orientations are formed in these openings and solid portions by an oblique electric field (Patent Document 1). When this method is used, the liquid crystal domain having the radial tilt alignment is formed stably and has high continuity, so that viewing angle characteristics and display quality can be improved.
JP 2003-043525 A

  However, with the widespread use of liquid crystal display devices, the display characteristics required for liquid crystal display devices are increasing, and a higher aperture ratio is desired for performing brighter display.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a liquid crystal display device having wide viewing angle characteristics, high display quality, and capable of bright display.

  A liquid crystal display device according to the present invention comprises a first substrate, a second substrate, a liquid crystal layer provided between the first substrate and the second substrate, and has a plurality of pixel regions, The first substrate includes a pixel electrode provided for each of the plurality of pixel regions on the liquid crystal layer side, and a switching element electrically connected to the pixel electrode, and the second substrate Has a counter electrode facing the pixel electrode through the liquid crystal layer, and in each of the plurality of pixel regions, the pixel electrode has a solid part including a plurality of unit solid parts. The liquid crystal layer assumes a vertical alignment state when no voltage is applied between the pixel electrode and the counter electrode, and a voltage is applied between the pixel electrode and the counter electrode. Is generated obliquely around each of the plurality of unit solid portions of the picture element electrode. A liquid crystal display device in which a liquid crystal domain having a radially inclined alignment state is formed in a region corresponding to each of the plurality of unit solid portions by a boundary, wherein each of the plurality of pixel regions includes the pixel element. And an auxiliary capacitor electrically connected in parallel to a liquid crystal capacitor constituted by the electrode, the counter electrode, and the liquid crystal layer, and the first substrate includes the pixel element in each of the plurality of pixel regions. A region where the solid portion of the electrode is not provided, and at least a part of the auxiliary capacitance is located in a region where the solid portion of the first substrate is not provided, whereby the object Is achieved.

  In a preferred embodiment, the switching element is a thin film transistor.

  In a preferred embodiment, the auxiliary capacitor includes an auxiliary capacitor line, an auxiliary capacitor electrode facing the auxiliary capacitor line and electrically connected to a drain electrode of the thin film transistor, the auxiliary capacitor line, and the auxiliary capacitor. And a first insulating layer provided between the electrodes.

  In a preferred embodiment, at least a part of the storage capacitor line, at least a part of the storage capacitor electrode, and at least a part of the first insulating layer are located in the region.

  In a preferred embodiment, the first substrate has a scanning wiring electrically connected to the gate electrode of the thin film transistor and a signal wiring electrically connected to the source electrode of the thin film transistor.

  In a preferred embodiment, the auxiliary capacitance wiring has at least one wiring trunk extending substantially parallel to the scanning wiring, and a wiring branch extending from the wiring trunk, and the auxiliary capacitance electrode includes: The wiring trunk includes at least one electrode trunk opposed to the wiring trunk via the first insulating layer, and an electrode branch extending from the electrode trunk.

  In a preferred embodiment, the wiring branch portion and the electrode branch portion are extended so as to overlap one central portion of the plurality of unit solid portions.

  In a preferred embodiment, the at least one wiring trunk is a plurality of wiring trunks, and the at least one electrode trunk is a plurality of electrode trunks.

  Preferably, the first substrate further includes a second insulating layer that covers at least the thin film transistor and the auxiliary capacitance electrode, and the pixel electrode is formed on the second insulating layer.

  The second insulating layer is preferably formed of a resin material.

  Each of the plurality of unit solid portions preferably has rotational symmetry.

  In a preferred embodiment, each of the plurality of unit solid portions has a substantially circular shape.

  In a preferred embodiment, each of the plurality of unit solid portions has a substantially rectangular shape with corners having a substantially arc shape.

  In a preferred embodiment, each of the plurality of unit solid portions has a shape in which a corner portion is sharpened.

  Preferably, the plurality of unit solid portions form at least one unit cell that is substantially the same shape, has the same size, and is arranged to have rotational symmetry.

  In a preferred embodiment, the pixel electrode further includes at least one opening, and the liquid crystal layer is oblique when the voltage is applied between the pixel electrode and the counter electrode. A liquid crystal domain having a radially inclined alignment state is formed in a region corresponding to the at least one opening by an electric field.

  The at least one opening includes a plurality of openings having substantially the same shape and the same size, and at least some of the openings are arranged to have rotational symmetry. Preferably, at least one unit cell is formed.

  Each shape of the at least some of the plurality of openings preferably has rotational symmetry.

  In a preferred embodiment, each of the at least some of the plurality of openings has a substantially circular shape.

  In each of the plurality of picture element regions, it is preferable that the total area of the plurality of openings of the picture element electrode is smaller than the area of the solid part of the picture element electrode.

  In a preferred embodiment, the liquid crystal display device according to the present invention further includes a convex portion inside each of the plurality of openings of the pixel electrode, and the cross-sectional shape of the convex portion in the in-plane direction of the substrate is The shape of the plurality of openings is the same, and the side surface of the convex portion has an alignment regulating force in the same direction as the alignment regulating direction by the oblique electric field with respect to the liquid crystal molecules of the liquid crystal layer.

  In a preferred embodiment, the first substrate includes a dielectric layer provided on a side opposite to the liquid crystal layer of the pixel electrode, and the at least one of the pixel electrode via the dielectric layer. A further electrode facing at least a portion of the opening.

  In a preferred embodiment, in the second substrate, a voltage is applied between at least the pixel electrode and the counter electrode in a region corresponding to each of the plurality of unit solid portions. It has an alignment control structure that expresses an alignment control force that causes radial tilt alignment in an applied state.

  It is preferable that the orientation restricting structure is provided in a region corresponding to the vicinity of the center of each of the plurality of unit solid portions.

  In the liquid crystal domain formed corresponding to each of the plurality of unit solid portions, it is preferable that the alignment control direction by the alignment control structure is aligned with the direction of the radial tilt alignment by the oblique electric field.

  In a preferred embodiment, the alignment regulating structure develops an alignment regulating force even when no voltage is applied between the pixel electrode and the counter electrode.

  In a preferred embodiment, the alignment regulating structure is a protrusion protruding toward the liquid crystal layer of the counter substrate.

  In a preferred embodiment, a part of the auxiliary capacitor overlaps the orientation regulating structure.

  In a preferred embodiment, the liquid crystal domain assumes a spiral radial tilt alignment state.

  Another liquid crystal display device according to the present invention includes a first substrate, a second substrate, and a liquid crystal layer provided between the first substrate and the second substrate, and has a plurality of pixel regions. The first substrate includes a pixel electrode provided for each of the plurality of pixel regions on the liquid crystal layer side, and a switching element electrically connected to the pixel electrode. The two substrates have a counter electrode facing the pixel electrode through the liquid crystal layer, and in each of the plurality of pixel regions, the pixel electrode has at least one opening or slit, The liquid crystal layer is in a vertical alignment state when no voltage is applied between the pixel electrode and the counter electrode, and a voltage is applied between the pixel electrode and the counter electrode. Sometimes the at least one opening or slit of the picture element electrode A liquid crystal display device, the alignment of which is regulated by an oblique electric field generated at an edge portion, wherein each of the plurality of pixel regions includes the pixel electrode, the counter electrode, and the liquid crystal layer. And at least a portion of the auxiliary capacitor overlaps the at least one opening or slit of the pixel electrode, thereby achieving the object.

  In a preferred embodiment, the switching element is a thin film transistor.

  In a preferred embodiment, the auxiliary capacitor includes an auxiliary capacitor line, an auxiliary capacitor electrode facing the auxiliary capacitor line and electrically connected to a drain electrode of the thin film transistor, the auxiliary capacitor line, and the auxiliary capacitor. And a first insulating layer provided between the electrodes.

  Preferably, the first substrate further includes a second insulating layer that covers at least the thin film transistor and the auxiliary capacitance electrode, and the pixel electrode is formed on the second insulating layer.

  The second insulating layer is preferably formed of a resin material.

  In a preferred embodiment, at least one opening or slit of the pixel electrode is a plurality of slits.

  In a preferred embodiment, the second substrate includes a plurality of ribs provided in regions corresponding to the plurality of slits of the pixel electrode.

  Alternatively, the counter electrode has a plurality of further slits provided in a corresponding region between the plurality of slits of the pixel electrode.

  Hereinafter, the operation of the present invention will be described.

  In the liquid crystal display device according to the present invention, the pixel electrode provided for each pixel region has a solid part including a plurality of unit solid parts, and the liquid crystal layer is vertically aligned in a state in which no voltage is applied. In a voltage application state, a plurality of liquid crystal domains having a radially inclined alignment state are formed by an oblique electric field generated around each of the plurality of unit solid portions. In other words, when a voltage is applied between the pixel electrode and the counter electrode, the outer shape of the pixel electrode is formed so that a slant electric field is generated around the unit solid part to form a liquid crystal domain having a radial tilt alignment. Is stipulated. The liquid crystal layer is typically made of a liquid crystal material having negative dielectric anisotropy, and the alignment is regulated by vertical alignment layers (for example, vertical alignment films) provided on both sides thereof.

  The liquid crystal domain formed by the oblique electric field is formed in a region corresponding to the unit solid part, and display is performed by changing the alignment state of the liquid crystal domain according to the voltage. Each liquid crystal domain has a radial tilt alignment and a highly rotationally symmetric alignment state, so that the viewing angle dependency of display quality is small and a wide viewing angle characteristic is realized.

  A portion where the conductive film exists in the pixel electrode is referred to as a solid portion, and a portion in the solid portion that generates an electric field forming one liquid crystal domain is referred to as a “unit solid portion”. The solid part is typically formed from a continuous conductive film.

  In the liquid crystal display device according to the present invention, since at least a part of the auxiliary capacitor is located in a region where the solid portion of the pixel electrode is not provided, typically, it includes a light shielding member. A reduction in effective aperture ratio (transmittance) due to the auxiliary capacitance configured can be suppressed, and the area of the solid part contributing to display can be increased. Therefore, bright display is realized.

  From the viewpoint of sufficiently improving the aperture ratio, it is preferable that as many portions as possible of the auxiliary capacity are located in a region where the solid portion is not provided. Specifically, it is preferable that ¼ or more of the auxiliary capacity is located in a region where no solid part is provided, more preferably ½ or more, and almost all are located. More preferably.

  As the switching element electrically connected to the pixel electrode, for example, a thin film transistor can be used.

  Typically, the auxiliary capacitance is provided between the auxiliary capacitance wiring, the auxiliary capacitance electrode facing the auxiliary capacitance wiring and electrically connected to the drain electrode of the thin film transistor, and the auxiliary capacitance wiring and the auxiliary capacitance electrode. And at least a part of the auxiliary capacitance wiring, at least a part of the auxiliary capacitance electrode, and at least a part of the dielectric layer are located in a region where the solid part is not provided. ing.

  In addition, one of the pair of substrates opposed to each other with a liquid crystal layer provided with a thin film transistor typically includes a scanning wiring electrically connected to the gate electrode of the thin film transistor and an electric source connected to the source electrode of the thin film transistor. Signal wiring connected to each other.

  Since the auxiliary capacitance wiring and the auxiliary capacitance electrode have a branch structure, it is possible to design with a high degree of freedom with respect to the arrangement of the auxiliary capacitance in the pixel region, and a sufficient capacitance value is ensured. An effective aperture ratio can be obtained. Specifically, the auxiliary capacitance wiring has at least one wiring trunk extending substantially parallel to the scanning wiring, and a wiring branch extending from the wiring trunk, and the auxiliary capacitance electrode is connected to the wiring trunk by the first. By adopting a configuration having at least one electrode trunk portion facing through the insulating layer and an electrode branch portion extending from the electrode trunk portion, such an effect can be obtained. The wiring branch and the electrode branch are extended so as to overlap, for example, near the center of the unit solid part.

  Further, since the auxiliary capacitance wiring has a plurality of wiring trunks and the auxiliary capacitance electrode has a plurality of electrode trunks, the degree of freedom in design can be further increased, and a larger portion of the auxiliary capacitance can be provided as a solid portion. Therefore, it is possible to realize a design with a higher aperture ratio.

  When the substrate having the picture element electrode further includes a second insulating layer covering at least the thin film transistor and the auxiliary capacitance electrode, and the picture element electrode is formed on the second insulating layer, the picture element electrode is adopted. Can be provided so as to partially overlap with the thin film transistor and the wiring, and the aperture ratio can be further improved.

  In order to generate an oblique electric field having a strength sufficient to obtain a radially inclined alignment, it is preferable that the second insulating layer is a thick film. The auxiliary capacitance electrode constituting the auxiliary capacitance is electrically connected to the drain electrode of the thin film transistor, and has substantially the same potential as the solid part of the pixel electrode. Therefore, if a part of the auxiliary capacitance electrode is located in a region where the solid part is not provided, the equipotential lines generated at the time of voltage application are not sufficiently lowered in the region where the solid part is not provided, An oblique electric field with sufficient strength may not be generated around the unit solid part. When the second insulating layer is made thick, the voltage drop due to the second insulating layer can be sufficiently increased, and the equipotential line can be sufficiently lowered in the region where the solid part is not provided. An oblique electric field having a sufficient strength can be generated around the portion. Further, since the surface of the second insulating layer on the liquid crystal layer side can be made substantially flat by making the second insulating layer thick, the solid state of the pixel electrode formed thereon is solid. It is possible to prevent a step from occurring in the part. In order to obtain a sufficiently stable radial gradient orientation, the thickness of the second insulating layer is preferably 1 μm or more, and more preferably 2.5 μm or more.

  When the second insulating layer is formed from a resin material (for example, a transparent resin material having photosensitivity), it is easy to increase the thickness of the second insulating layer.

  The shape of the unit solid part (the shape when viewed from the normal direction of the substrate) has rotational symmetry, thereby improving the stability of the radial tilt alignment of the liquid crystal domain formed in the region corresponding to the unit solid part. be able to. In order to reduce the viewing angle dependency of the liquid crystal domain, it is preferable that the shape of the unit solid portion has high rotational symmetry (preferably two-fold rotational symmetry or more, and more preferably four-fold rotational symmetry or more). .

  When the unit solid part has a substantially circular shape or an elliptical shape, the alignment continuity of the liquid crystal molecules in the radially inclined alignment state is increased, so that the alignment stability is improved.

  On the other hand, when the shape of the unit solid part is substantially rectangular, the area ratio (effective aperture ratio) of the unit solid part in the pixel region is high, so that the optical characteristics with respect to the voltage of the liquid crystal layer (for example, (Transmittance) is improved.

  Moreover, when the shape of the unit solid part is a substantially rectangular shape with corners having a substantially arc shape, both the alignment stability and the optical characteristics can be improved.

  Further, when the unit solid part has a shape with a sharpened corner (for example, a substantially star shape), more sides of the electrode that generates the oblique electric field are formed, so that more oblique liquid crystal molecules are applied to the liquid crystal molecules. Can act. Therefore, the response speed is improved.

  A plurality of unit solid portions have substantially the same shape, the same size, and at least one unit cell arranged to have rotational symmetry, thereby forming the unit cell as a unit. As described above, since a plurality of liquid crystal domains can be arranged with high symmetry, the viewing angle dependency of display quality can be improved. Furthermore, by dividing the entire picture element region into unit cells, the alignment of the liquid crystal layer can be stabilized over the entire picture element region. For example, the plurality of unit solid parts are arranged so that the center of each unit solid part forms a square lattice.

  The pixel electrode may further have at least one opening. By providing openings in the pixel electrodes, it becomes easy to form many unit solid parts, and many liquid crystal domains can be easily formed in the pixel region.

  When the opening is provided, a liquid crystal domain having a radially inclined alignment state can be formed in a region corresponding to the opening by an oblique electric field generated around the unit solid portion, that is, at the edge of the opening. Since the liquid crystal domain formed in the unit solid part and the liquid crystal domain formed in the opening are formed by the oblique electric field, they are alternately formed adjacent to each other, and the liquid crystal between the adjacent liquid crystal domains is formed. The molecular orientation is essentially continuous. Therefore, a disclination line is not generated between the liquid crystal domain formed in the opening and the liquid crystal domain formed in the solid portion, thereby preventing deterioration in display quality and stability of alignment of liquid crystal molecules. Is also expensive.

  If the liquid crystal molecules take a radial tilt alignment not only in the region corresponding to the solid part of the pixel electrode but also in the region corresponding to the opening, the alignment of the liquid crystal molecules is highly continuous and a stable alignment state is realized. A uniform display without roughness is obtained. In particular, in order to achieve good response characteristics (fast response speed), it is preferable to apply an oblique electric field for controlling the alignment of the liquid crystal molecules to many liquid crystal molecules. ) Is preferably formed. When a liquid crystal domain having a stable radial tilt alignment is formed corresponding to the opening, even if many openings are formed in order to improve the response characteristics, the display quality is lowered (occurrence of roughness). Can be suppressed.

  If a liquid crystal domain having a radial tilt alignment corresponding to the solid portion (unit solid portion) is formed, the liquid crystal domain formed corresponding to the opening does not have a radial tilt alignment. Since the continuity of the alignment of the liquid crystal molecules in the region can be obtained, the radial tilt alignment of the liquid crystal domain formed corresponding to the solid part is stable. In particular, when the area of the opening is small, the contribution to the display is small. Therefore, even if a liquid crystal domain having a radially inclined alignment is not formed in a region corresponding to the opening, the display quality does not deteriorate.

  By forming at least one unit cell in which at least some of the plurality of openings have substantially the same shape and the same size and are arranged to have rotational symmetry Since the plurality of liquid crystal domains can be arranged with high symmetry using the unit cell as a unit, the viewing angle dependency of display quality can be improved. Furthermore, by dividing the entire picture element region into unit cells, the alignment of the liquid crystal layer can be stabilized over the entire picture element region. For example, the openings are arranged so that the centers of the openings form a square lattice.

  Each of the openings (typically, the openings forming the unit cell) of the plurality of openings has a rotational symmetry in the shape (the shape when viewed from the substrate normal direction). The stability of the radial tilt alignment of the liquid crystal domain formed in the portion can be enhanced. In order to reduce the viewing angle dependence of the liquid crystal domain, it is preferable that the shape of the opening has a high rotational symmetry (preferably two-fold rotational symmetry or more, and more preferably four-fold rotational symmetry or more).

  The shape of the opening (the shape when viewed from the normal direction of the substrate) is, for example, a substantially circular shape or a substantially regular polygon shape (for example, a square shape).

  In each of the pixel regions, the total area of the openings formed in the electrode is preferably smaller than the area of the solid part. The larger the area of the solid part, the larger the area of the liquid crystal layer that is directly affected by the electric field generated by the electrode (defined in the plane when viewed from the normal direction of the substrate). The optical characteristics (for example, the transmittance) with respect to the voltage are improved.

  Whether to adopt a configuration in which the opening is substantially circular or a configuration in which the unit solid portion is substantially circular may be determined depending on which configuration can increase the area of the solid portion. Which configuration is preferred is appropriately selected depending on the pitch of the picture elements. Typically, when the pitch exceeds about 25 μm, the opening is preferably formed so that the solid part is substantially circular, and when it is about 25 μm or less, the opening is preferably substantially circular. .

  Further, in order to improve resistance to stress, a convex portion having a side surface having an alignment regulating force in the same direction as the alignment regulating direction by the oblique electric field described above is arranged inside the opening of the electrode with respect to the liquid crystal molecules of the liquid crystal layer. May be provided. The cross-sectional shape of the convex portion in the in-plane direction of the substrate is the same as the shape of the opening, and it is preferable to have rotational symmetry similar to the shape of the opening described above. However, since the liquid crystal molecules whose alignment is regulated by the alignment regulating force on the side surface of the convex part hardly responds to the voltage (the change in retardation due to the voltage is small), this causes a reduction in the contrast ratio of the display. Therefore, it is preferable to set the size, height, and number of the convex portions so as not to deteriorate the display quality.

  In the electrode structure in which the opening is provided in one of the pair of electrodes described above, a sufficient voltage is not applied to the liquid crystal layer in a region corresponding to the opening, and a sufficient retardation change cannot be obtained. There may be a problem that the utilization efficiency is lowered. Therefore, a dielectric layer is provided on the side opposite to the liquid crystal layer of the electrode provided with the opening, and an additional electrode facing at least a part of the opening of the electrode is provided via this dielectric layer (two-layer structure electrode) Thus, a sufficient voltage can be applied to the liquid crystal layer corresponding to the opening, and light utilization efficiency and response characteristics can be improved.

  The substrate (opposite substrate) facing the substrate provided with the pixel electrode has an alignment regulating force that causes the liquid crystal molecules of the liquid crystal layer to be radially inclined and aligned at least in a voltage applied state in a region corresponding to each of the plurality of unit solid portions. When the orientation regulation structure is expressed, at least in the voltage applied state, the orientation regulation force due to the pixel electrode having the unit solid part and this orientation regulation structure acts on the liquid crystal molecules, so that the radial direction of the liquid crystal domain The tilt alignment is further stabilized, and the deterioration of display quality (for example, occurrence of afterimage reduction) due to the application of stress to the liquid crystal layer is suppressed.

  By providing the alignment regulating structure in a region corresponding to the vicinity of the center of the unit solid part, the position of the central axis of the radial inclined alignment can be fixed, so that the resistance to the stress of the radial inclined alignment is effectively improved. .

  In the liquid crystal domain formed corresponding to the solid part of the unit, if the alignment control direction by the alignment control structure is set to match the direction of the radial tilt alignment by the oblique electric field, alignment continuity and stability increase. Display quality and response characteristics are improved.

  The orientation regulating structure can achieve the effect of stabilizing the orientation if it exerts an orientation regulating force at least in a voltage applied state. However, if a configuration that exerts the orientation regulating force in a voltage non-applied state is adopted, the magnitude of the applied voltage Regardless, the advantage that the orientation can be stabilized is obtained. Since the orientation regulating force of the orientation regulating structure is effective even if it is relatively weak, the orientation can be sufficiently stabilized even with a structure smaller than the size of the picture element. Therefore, the alignment regulating structure only needs to exhibit an alignment regulating force that is weaker than the alignment regulating force of the pixel electrode having the unit solid part, and can be realized using various structures.

  The alignment regulating structure is, for example, a convex portion protruding toward the liquid crystal layer side of the substrate. The convex portion can express the orientation regulating force even in the state where no voltage is applied. Moreover, since such a convex part can be manufactured with a simple process, it is preferable also from a viewpoint of production efficiency.

  However, since a vertical alignment type liquid crystal layer in which liquid crystal molecules are aligned substantially perpendicularly to the substrate surface in the absence of voltage application, an alignment regulation structure that expresses alignment regulation force in the absence of voltage application is used. This is accompanied by a decrease in display quality. However, since the alignment control force of the alignment control structure is effective even if it is relatively weak, it is possible to sufficiently stabilize the alignment even with a structure smaller than the size of the picture element, and display when no voltage is applied Degradation may not be a substantial problem. Depending on the application of the liquid crystal display device (for example, the magnitude of the stress applied from the outside) and the electrode configuration (strength of the alignment regulating force by the pixel electrode), an alignment regulating structure that exhibits a relatively strong alignment regulating force may be used. May be provided. In such a case, a light shielding layer may be provided in order to suppress deterioration in display quality due to the alignment regulation structure. In this case, a part of the auxiliary capacitor may be overlapped with the alignment regulating structure to function as a light shielding layer. With such a configuration, a sufficiently large capacitance value can be ensured without an excessive decrease in brightness.

  In addition, by adopting a configuration in which the liquid crystal domain has a spiral radial inclined alignment state, the alignment is further stabilized, uniform display without roughness is realized, and the response speed is improved. The spiral radial tilt alignment state is realized, for example, by using a material obtained by adding a chiral agent to a nematic liquid crystal material having negative dielectric anisotropy. Whether it is clockwise or counterclockwise depends on the type of chiral agent used.

  In another liquid crystal display device according to the present invention, a picture element electrode provided for each picture element region has an opening or a slit, and the liquid crystal layer assumes a vertical alignment state when no voltage is applied, and In the voltage application state, the orientation is regulated by an oblique electric field generated at the opening or the edge of the slit, thereby displaying. In another liquid crystal display device according to the present invention, since at least a part of the auxiliary capacitor overlaps with the opening or slit of the pixel electrode, the effective opening caused by the auxiliary capacitor typically including a light-shielding member is provided. It is possible to suppress a reduction in the transmittance (transmittance) and increase the area of the region contributing to display (the portion of the pixel electrode where the conductive film exists). Therefore, bright display is realized.

  From the viewpoint of sufficiently improving the aperture ratio, it is preferable that as many portions of the auxiliary capacity as possible overlap with the openings or slits. Specifically, it is preferable that 1/4 or more of the auxiliary capacity overlap, more preferably 1/2 or more overlap, and still more preferably substantially all overlap.

  As the switching element electrically connected to the pixel electrode, for example, a thin film transistor can be used.

  Typically, the auxiliary capacitance is provided between the auxiliary capacitance wiring, the auxiliary capacitance electrode facing the auxiliary capacitance wiring and electrically connected to the drain electrode of the thin film transistor, and the auxiliary capacitance wiring and the auxiliary capacitance electrode. And a first insulating layer.

  When the substrate having the picture element electrode further includes a second insulating layer covering at least the thin film transistor and the auxiliary capacitance electrode, and the picture element electrode is formed on the second insulating layer, the picture element electrode is adopted. Can be provided so as to partially overlap with the thin film transistor and the wiring, and the aperture ratio can be further improved.

  In order to generate an oblique electric field having a sufficient strength for regulating the orientation, it is preferable that the second insulating layer is a thick film. The auxiliary capacitance electrode constituting the auxiliary capacitance is electrically connected to the drain electrode of the thin film transistor and has substantially the same potential as the conductive film of the pixel electrode. For this reason, if a part of the auxiliary capacitance electrode overlaps the opening or slit, the equipotential lines generated at the time of voltage application are not sufficiently lowered at the opening or slit, and the opening or slit edge is sufficiently strong. An oblique electric field may not be generated. If the second insulating layer is made thick, the voltage drop due to the second insulating layer can be made sufficiently large, and the equipotential lines can be sufficiently lowered by the opening or slit, so that the opening or the edge of the slit is formed. An oblique electric field with sufficient strength can be generated. Further, since the surface of the second insulating layer on the liquid crystal layer side can be made substantially flat by making the second insulating layer thick, there is a step in the pixel electrode formed thereon. It can be prevented from occurring. In order to obtain a sufficiently strong alignment regulating force, the thickness of the second insulating layer is preferably 1 μm or more, and more preferably 2.5 μm or more.

  When the second insulating layer is formed from a resin material (for example, a transparent resin material having photosensitivity), it is easy to increase the thickness of the second insulating layer.

  According to the present invention, a liquid crystal display device having a wide viewing angle characteristic, high display quality, and capable of bright display is provided.

  According to the present invention, since the liquid crystal domain having the radial tilt alignment is stably formed with high continuity, the display quality of the conventional liquid crystal display device having a wide viewing angle characteristic can be further improved.

  Further, since at least a part of the auxiliary capacitor is located in a region where the solid portion of the pixel electrode is not provided, the auxiliary capacitor is typically caused by the auxiliary capacitor including a light-shielding member. A decrease in effective aperture ratio (transmittance) can be suppressed, and the area of the solid portion contributing to display can be increased. Therefore, bright display is realized.

  Alternatively, according to the present invention, since at least a part of the auxiliary capacitor overlaps with the opening or slit of the pixel electrode, a decrease in effective aperture ratio (transmittance) due to the auxiliary capacitor is suppressed, and a bright display is achieved. Can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, the electrode structure and the operation of the liquid crystal display device of the present invention will be described. Hereinafter, an embodiment of the present invention will be described for an active matrix liquid crystal display device using a thin film transistor (TFT). In the following, embodiments of the present invention will be described by taking a transmissive liquid crystal display device as an example. However, the present invention is not limited to this, and can be applied to a reflective liquid crystal display device and a transflective liquid crystal display device. it can.

  In the present specification, an area of the liquid crystal display device corresponding to “picture element” which is the minimum unit of display is referred to as “picture element area”. In the color liquid crystal display device, “picture elements” of R, G, and B correspond to one “pixel”. The picture element region is typically defined by a picture element electrode and a counter electrode facing the picture element electrode. Strictly speaking, in the configuration in which the black matrix is provided, the region corresponding to the opening of the black matrix corresponds to the pixel region in the region to which the voltage is applied according to the state to be displayed. .

  The structure of one picture element region of the liquid crystal display device 100 according to the embodiment of the present invention will be described with reference to FIGS. In the following, a color filter and a black matrix are omitted for the sake of simplicity. In the following drawings, components having substantially the same functions as the components of the liquid crystal display device 100 are denoted by the same reference numerals, and description thereof is omitted. FIG. 1A is a top view as viewed from the normal direction of the substrate, and FIG. 1B corresponds to a cross-sectional view taken along the line 1B-1B ′ in FIG. FIG. 1B shows a state where no voltage is applied to the liquid crystal layer.

  The liquid crystal display device 100 is provided between an active matrix substrate (hereinafter referred to as “TFT substrate”) 100a, a counter substrate (also referred to as “color filter substrate”) 100b, and the TFT substrate 100a and the counter substrate 100b. And a liquid crystal layer 30. The liquid crystal molecules 30a of the liquid crystal layer 30 have negative dielectric anisotropy, and a vertical alignment film (not shown) as a vertical alignment layer provided on the surface of the TFT substrate 100a and the counter substrate 100b on the liquid crystal layer 30 side. Thus, when no voltage is applied to the liquid crystal layer 30, as shown in FIG. 1B, the liquid crystal layer 30 is aligned perpendicular to the surface of the vertical alignment film. At this time, the liquid crystal layer 30 is said to be in a vertically aligned state. However, the liquid crystal molecules 30a of the liquid crystal layer 30 in the vertical alignment state may be slightly inclined from the normal line of the surface of the vertical alignment film (substrate surface) depending on the type of the vertical alignment film and the type of the liquid crystal material. In general, a state in which liquid crystal molecular axes (also referred to as “axis orientation”) are aligned at an angle of about 85 ° or more with respect to the surface of the vertical alignment film is called a vertical alignment state.

  The TFT substrate 100a of the liquid crystal display device 100 includes a transparent substrate (for example, a glass substrate) 11 and pixel electrodes 14 formed on the surface thereof. The counter substrate 100b includes a transparent substrate (for example, a glass substrate) 21 and a counter electrode 22 formed on the surface thereof. The alignment state of the liquid crystal layer 30 for each pixel region changes according to the voltage applied to the pixel electrode 14 and the counter electrode 22 arranged so as to face each other via the liquid crystal layer 30. Display is performed using a phenomenon in which the polarization state and amount of light transmitted through the liquid crystal layer 30 change in accordance with the change in the alignment state of the liquid crystal layer 30.

  The pixel electrode 14 included in the liquid crystal display device 100 has a plurality of openings 14a and solid portions 14b. The opening 14a indicates a portion of the pixel electrode 14 formed from a conductive film (for example, an ITO film) from which the conductive film is removed, and the solid portion 14b indicates a portion where the conductive film exists (other than the opening 14a). Point). A plurality of openings 14a are formed for each pixel electrode, but the solid part 14b is basically formed of a single continuous conductive film.

  The plurality of openings 14a are arranged so that the centers thereof form a square lattice, and are substantially surrounded by the four openings 14a whose centers are located on the four lattice points forming one unit lattice. The solid part (referred to as “unit solid part”) 14 b ′ has a substantially circular shape. Each of the openings 14a has a substantially star shape having four quarter arc sides (edges) and a four-fold rotation axis at the center thereof. Here, in order to stabilize the alignment over the entire picture element region, a unit cell is formed up to the end of the picture element electrode 14. In other words, as shown in the figure, the end of the pixel electrode 14 is approximately one half of the opening 14a located in the center of the pixel electrode 14 (a region corresponding to the side) and approximately one quarter (a corner). And an opening 14 a is also arranged at the end of the picture element electrode 14.

  The opening 14a located at the center of the picture element region has substantially the same shape and the same size. The unit solid portion 14b 'located in the unit lattice formed by the openings 14a is substantially circular, and has substantially the same shape and the same size. The unit solid portions 14b 'adjacent to each other are connected to each other, and constitute a solid portion 14b that substantially functions as a single conductive film.

  When a voltage is applied between the pixel electrode 14 and the counter electrode 22 having the above-described configuration, a plurality of liquid crystal domains each having a radial tilt alignment are formed by an oblique electric field generated at the edge portion of the opening 14a. It is formed. One liquid crystal domain is formed in each of a region corresponding to each opening 14a and a region corresponding to the unit solid portion 14b 'in the unit lattice.

  Here, the square pixel electrode 14 is illustrated, but the shape of the pixel electrode 14 is not limited thereto. Since the general shape of the pixel electrode 14 is approximated to a rectangle (including a square and a rectangle), the openings 14a can be regularly arranged in a square lattice shape. Even if the pixel electrode 14 has a shape other than a rectangle, the openings 14a are formed regularly (for example, in a square lattice shape as illustrated) so that the liquid crystal domains are formed in all regions within the pixel region. If it arrange | positions, the effect of this invention can be acquired.

  Further, here, a configuration in which a plurality of openings 14a are provided in one picture element region is illustrated, but a plurality of liquid crystal domains can be formed in one picture element region only by providing one opening. For example, when attention is paid to a square region composed of four units divided by broken lines shown in FIG. 1A and this is regarded as one pixel electrode, this pixel electrode has one opening portion. 14 a and four unit solid portions 14 b ′ arranged in the periphery thereof, but when a voltage is applied, five liquid crystal domains having a radial tilt alignment are formed.

  Furthermore, a plurality of liquid crystal domains can be formed in one picture element region without forming the opening 14a. For example, when attention is paid to two units adjacent to each other and this is considered as one picture element electrode, this picture element electrode is composed of two unit solid parts 14b 'and does not have an opening part 14a. At the time of application, two liquid crystal domains having a radially inclined alignment are formed. As described above, if the pixel electrode has at least the unit solid portion 14b ′ that forms a plurality of liquid crystal domains having a radially inclined orientation when a voltage is applied (in other words, it has such an outer shape. If this is the case, the continuity of the alignment of the liquid crystal molecules 30a in the pixel region can be obtained, so that the radial tilt alignment of the liquid crystal domain formed corresponding to the unit solid portion 14b ′ is stable.

  The mechanism by which liquid crystal domains are formed by the above-described oblique electric field will be described with reference to FIGS. 2 (a) and 2 (b). 2A and 2B show a state in which a voltage is applied to the liquid crystal layer 30 shown in FIG. 1B, respectively. FIG. 2A shows the voltage applied to the liquid crystal layer 30. Accordingly, a state in which the orientation of the liquid crystal molecules 30a starts to change (ON initial state) is schematically shown, and FIG. 2B shows that the orientation of the liquid crystal molecules 30a changed according to the applied voltage is steady. The state which reached the state is shown typically. A curve EQ in FIGS. 2A and 2B shows an equipotential line EQ.

  When the pixel electrode 14 and the counter electrode 22 are at the same potential (a state in which no voltage is applied to the liquid crystal layer 30), as shown in FIG. 1A, the liquid crystal molecules 30a in the pixel region are , Oriented perpendicular to the surfaces of both substrates 11 and 21.

  When a voltage is applied to the liquid crystal layer 30, a potential gradient represented by an equipotential line EQ (perpendicular to the electric force lines) shown in FIG. This equipotential line EQ is parallel to the surface of the solid portion 14b and the counter electrode 22 in the liquid crystal layer 30 located between the solid portion 14b of the picture element electrode 14 and the counter electrode 22, and It falls in a region corresponding to the opening 14a of the elementary electrode 14 and is inclined in the liquid crystal layer 30 on the edge portion of the opening 14a (the inner periphery of the opening 14a including the boundary (extended) of the opening 14a). An oblique electric field represented by an equipotential line EQ is formed.

  A torque is applied to the liquid crystal molecules 30a having negative dielectric anisotropy so as to align the axial direction of the liquid crystal molecules 30a in parallel to the equipotential lines EQ (perpendicular to the lines of electric force). Accordingly, the liquid crystal molecules 30a on the edge portion EG are rotated clockwise in the right edge portion EG in the drawing and counterclockwise in the left edge portion EG in the drawing, as indicated by an arrow in FIG. Each direction is inclined (rotated) and oriented parallel to the equipotential line EQ.

  Here, the change in the alignment of the liquid crystal molecules 30a will be described in detail with reference to FIG.

  When an electric field is generated in the liquid crystal layer 30, a torque is applied to the liquid crystal molecules 30a having negative dielectric anisotropy so as to align the axial direction parallel to the equipotential line EQ. As shown in FIG. 3A, when an electric field represented by an equipotential line EQ perpendicular to the axial direction of the liquid crystal molecules 30a is generated, the liquid crystal molecules 30a are tilted clockwise or counterclockwise. Acts with equal probability of torque. Accordingly, in the liquid crystal layer 30 between the electrodes of the parallel plate type arrangement facing each other, the liquid crystal molecules 30a receiving the torque in the clockwise direction and the liquid crystal molecules 30a receiving the torque in the counterclockwise direction are mixed. As a result, the transition to the alignment state according to the voltage applied to the liquid crystal layer 30 may not occur smoothly.

  As shown in FIG. 2A, the electric field (diagonal) represented by an equipotential line EQ inclined with respect to the axial direction of the liquid crystal molecules 30a at the edge portion EG of the opening 14a of the liquid crystal display device 100 according to the present invention. When an electric field is generated, as shown in FIG. 3B, the liquid crystal molecules 30a are tilted in a direction with a small amount of tilt (counterclockwise in the illustrated example) to be parallel to the equipotential line EQ. Further, as shown in FIG. 3C, the liquid crystal molecules 30a located in the region where the electric field expressed by the equipotential line EQ perpendicular to the axis direction of the liquid crystal molecules 30a is inclined are equipotential. The liquid crystal molecules 30a positioned on the line EQ are tilted in the same direction as the liquid crystal molecules 30a positioned on the tilted equipotential line EQ so that the alignment is continuous (matched) with the liquid crystal molecules 30a. As shown in FIG. 3D, when an electric field that forms a continuous concavo-convex shape of the equipotential lines EQ is applied, the alignment is regulated by the liquid crystal molecules 30a positioned on the inclined equipotential lines EQ. The liquid crystal molecules 30a positioned on the flat equipotential lines EQ are aligned so as to match the direction. Note that “located on the equipotential line EQ” means “located within the electric field represented by the equipotential line EQ”.

  As described above, when the change in alignment starting from the liquid crystal molecules 30a located on the inclined equipotential line EQ progresses and reaches a steady state, the alignment state schematically shown in FIG. The liquid crystal molecules 30a located in the vicinity of the center of the opening 14a are almost equally affected by the orientation of the liquid crystal molecules 30a at the opposite edge portions EG of the opening 14a, and are therefore perpendicular to the equipotential line EQ. The liquid crystal molecules 30a in the region that maintains the alignment state and is away from the center of the opening 14a are inclined by the influence of the alignment of the liquid crystal molecules 30a in the closer edge portion EG, and are symmetric with respect to the center SA of the opening 14a. A tilted orientation is formed. This alignment state is a state in which the axial orientations of the liquid crystal molecules 30a are radially aligned with respect to the center of the opening 14a when viewed from the direction perpendicular to the display surface of the liquid crystal display device 100 (the direction perpendicular to the surfaces of the substrates 11 and 21). (Not shown). Therefore, in this specification, such an alignment state is referred to as “radially inclined alignment”. In addition, a region of the liquid crystal layer having a radially inclined alignment with respect to one center is referred to as a liquid crystal domain.

  Also in the region corresponding to the unit solid portion 14b 'substantially surrounded by the opening 14a, a liquid crystal domain in which the liquid crystal molecules 30a have a radially inclined alignment is formed. The liquid crystal molecules 30a in the region corresponding to the unit solid portion 14b ′ are affected by the alignment of the liquid crystal molecules 30a in the edge portion EG of the opening 14a, and the center SA (the opening 14a is formed by the unit solid portion 14b ′). A symmetric radial orientation with respect to the center of the unit cell.

  The radial tilt alignment in the liquid crystal domain formed in the unit solid portion 14b ′ and the radial tilt alignment formed in the opening 14a are continuous, and both are aligned with the alignment of the liquid crystal molecules 30a in the edge portion EG of the opening 14a. Oriented to do. The liquid crystal molecules 30a in the liquid crystal domain formed in the opening 14a are aligned in a cone shape with the upper side (substrate 100b side) open, and the liquid crystal molecules 30a in the liquid crystal domain formed in the unit solid portion 14b ′ are The side (substrate 100a side) is oriented in an open cone. Thus, since the radial tilt alignment formed in the liquid crystal domain formed in the opening 14a and the liquid crystal domain formed in the unit solid portion 14b ′ is continuous with each other, the disclination line ( (Alignment defect) is not formed, so that the display quality is not deteriorated due to the occurrence of the disclination line.

  In order to improve the viewing angle dependence of the display quality of the liquid crystal display device in all directions, the existence probability of the liquid crystal molecules aligned along each of all the azimuth directions in each pixel region has rotational symmetry. Preferably, it has an axial symmetry. That is, it is preferable that the liquid crystal domains formed over the entire picture element region are arranged so as to have rotational symmetry and further axial symmetry. However, it is not always necessary to have rotational symmetry over the entire pixel region, and liquid crystal domains arranged to have rotational symmetry (or axial symmetry) (for example, a plurality of pixels arranged in a square lattice pattern). The liquid crystal layer in the picture element region may be formed as an aggregate of liquid crystal domains. Accordingly, the arrangement of the plurality of openings 14a formed in the picture element region is not necessarily required to have rotational symmetry over the entire picture element region, and is arranged so as to have rotational symmetry (or axial symmetry). What is necessary is just to represent as an aggregate | assembly of the opening part (for example, the several opening part arranged in the square-lattice form). Of course, the arrangement of the unit solid portions 14b 'substantially surrounded by the plurality of openings 14a is the same. In addition, since the shape of each liquid crystal domain also preferably has rotational symmetry or axial symmetry, the shape of each opening 14a and unit solid portion 14b ′ also has rotational symmetry or axial symmetry. Is preferred.

  Note that a sufficient voltage is not applied to the liquid crystal layer 30 near the center of the opening 14a, and the liquid crystal layer 30 near the center of the opening 14a may not contribute to display. That is, even if the radial tilt alignment of the liquid crystal layer 30 near the center of the opening 14a is somewhat disturbed (for example, even if the central axis is shifted from the center of the opening 14a), the display quality may not be deteriorated. Accordingly, it is only necessary that the liquid crystal domains formed corresponding to at least the unit solid portion 14 b ′ have rotational symmetry and further axial symmetry.

  As described with reference to FIGS. 2A and 2B, the pixel electrode 14 of the liquid crystal display device 100 according to the present invention has a plurality of openings 14a, and the liquid crystal layer 30 in the pixel region. An electric field represented by an equipotential line EQ having an inclined region is formed therein. The liquid crystal molecules 30a having negative dielectric anisotropy in the liquid crystal layer 30 in the vertical alignment state when no voltage is applied change the alignment direction by using the alignment change of the liquid crystal molecules 30a located on the inclined equipotential line EQ as a trigger. Then, a liquid crystal domain having a stable radial tilt alignment is formed in the opening 14a and the solid portion 14b. Display is performed by changing the orientation of the liquid crystal molecules in the liquid crystal domain in accordance with the voltage applied to the liquid crystal layer.

  The shape (shape viewed from the substrate normal direction) of the opening 14a of the pixel electrode 14 included in the liquid crystal display device 100 of the present embodiment and the arrangement thereof will be described.

  The display characteristics of the liquid crystal display device show azimuth dependency due to the alignment state (optical anisotropy) of the liquid crystal molecules. In order to reduce the azimuth angle dependency of the display characteristics, it is preferable that the liquid crystal molecules are aligned with the same probability with respect to all azimuth angles. Further, it is more preferable that the liquid crystal molecules in each picture element region are aligned with the same probability with respect to all azimuth angles. Accordingly, the opening 14a preferably has a shape that forms a liquid crystal domain so that the liquid crystal molecules 30a in each pixel region are aligned with an equal probability with respect to all azimuth angles. . Specifically, the shape of the opening 14a preferably has rotational symmetry (preferably symmetry of two or more rotation axes) with each center (normal direction) as an axis of symmetry, The openings 14a are preferably arranged so as to have rotational symmetry. The shape of the unit solid portion 14b ′ substantially surrounded by the openings is also preferably rotationally symmetric, and the unit solid portion 14b ′ is also arranged to have rotational symmetry. preferable.

  However, the openings 14a and the unit solid portions 14b ′ are not necessarily arranged so as to have rotational symmetry over the entire picture element region. For example, as shown in FIG. If the pixel area is composed of the minimum unit (symmetry having a rotation axis of 4 times) and the combination thereof, the probability that the liquid crystal molecules are substantially equal to all azimuth angles over the entire pixel area. Can be oriented.

  The alignment state of the liquid crystal molecules 30a when the substantially star-shaped openings 14a having rotational symmetry and the substantially circular unit solid portions 14b shown in FIG. 1A are arranged in a square lattice is shown in FIG. A description will be given with reference to FIG.

  4A to 4C schematically show the alignment states of the liquid crystal molecules 30a viewed from the substrate normal direction. 4 (b) and (c) and the like showing the alignment state of the liquid crystal molecules 30a viewed from the normal direction of the substrate, the end of the liquid crystal molecules 30a drawn in an ellipse is shown in black. It is shown that the liquid crystal molecules 30a are inclined so that the end is closer to the substrate side on which the pixel electrode 14 having the opening 14a is provided than the other end. The same applies to the following drawings. Here, one unit cell (formed by four openings 14a) in the picture element region shown in FIG. 1A will be described. The cross sections along the diagonal lines in FIGS. 4A to 4C correspond to FIGS. 1B, 2A, and 2B, respectively, and are described with reference to these drawings together. To do.

  When the pixel electrode 14 and the counter electrode 22 are at the same potential, that is, when no voltage is applied to the liquid crystal layer 30, a vertical alignment layer (on the liquid crystal layer 30 side surfaces of the TFT substrate 100a and the counter substrate 100b) As shown in FIG. 4A, the liquid crystal molecules 30a whose alignment direction is regulated by an unillustrated state take a vertical alignment state.

  When an electric field is applied to the liquid crystal layer 30 and an electric field represented by the equipotential line EQ shown in FIG. 2A is generated, the liquid crystal molecules 30a having negative dielectric anisotropy have an axial orientation of equipotential. Torque is generated that is not parallel to the line EQ. As described with reference to FIGS. 3A and 3B, the liquid crystal molecules 30a under the electric field represented by the equipotential line EQ perpendicular to the molecular axis of the liquid crystal molecules 30a are tilted. Since the (rotating) direction is not uniquely determined (FIG. 3 (a)), the orientation change (tilt or rotation) does not easily occur, whereas it is tilted with respect to the molecular axis of the liquid crystal molecules 30a. In the liquid crystal molecules 30a placed under the potential line EQ, the tilt (rotation) direction is uniquely determined, so that the change in orientation easily occurs. Accordingly, as shown in FIG. 4B, the liquid crystal molecules 30a start to tilt from the edge portion of the opening 14a where the molecular axis of the liquid crystal molecules 30a is tilted with respect to the equipotential line EQ. Then, as described with reference to FIG. 3C, the surrounding liquid crystal molecules 30a are also tilted so as to be aligned with the alignment of the tilted liquid crystal molecules 30a at the edge of the opening 14a. ), The axial orientation of the liquid crystal molecules 30a is stabilized (radial tilt alignment).

  As described above, when the opening 14a has a rotationally symmetric shape, the liquid crystal molecules 30a in the picture element region are liquid crystal molecules 30a from the edge of the opening 14a toward the center of the opening 14a when a voltage is applied. Therefore, the liquid crystal molecules 30a in the vicinity of the center of the opening 14a in which the alignment regulating force of the liquid crystal molecules 30a from the edge portion is balanced maintain a state of being aligned perpendicular to the substrate surface, and the liquid crystal molecules 30a around the liquid crystal molecules 30a are aligned. A state is obtained in which the liquid crystal molecules 30a are continuously inclined radially about the liquid crystal molecules 30a near the center of the opening 14a.

  Further, liquid crystal molecules 30a in a region corresponding to the substantially circular unit solid portion 14b ′ surrounded by the four substantially star-shaped openings 14a arranged in a square lattice are also generated at the edge of the opening 14a. The liquid crystal molecules 30a are tilted so as to be aligned with the alignment of the tilted electric field. The liquid crystal molecules 30a in the vicinity of the center of the unit solid portion 14b ′ in which the alignment regulating force of the liquid crystal molecules 30a from the edge portion is balanced maintain a state of being aligned perpendicular to the substrate surface, and the surrounding liquid crystal molecules 30a are in the unit. A state is obtained in which the liquid crystal molecules 30a are continuously inclined radially about the liquid crystal molecules 30a near the center of the real part 14b ′.

  As described above, when the liquid crystal domains in which the liquid crystal molecules 30a have a radially inclined orientation are arranged in a square lattice pattern over the entire pixel region, the existence probabilities of the liquid crystal molecules 30a in the respective axial directions have rotational symmetry. As a result, high-quality display without roughness can be realized in all viewing angle directions. In order to reduce the viewing angle dependency of a liquid crystal domain having a radial tilt alignment, it is preferable that the liquid crystal domain has high rotational symmetry (two or more rotation axes are preferable, and four or more rotation axes are more preferable). In addition, in order to reduce the viewing angle dependency of the entire picture element region, a plurality of liquid crystal domains formed in the picture element region have high rotational symmetry (preferably a 2-fold rotation axis or more, and further a 4-fold rotation axis or more. It is preferable to constitute an array (for example, a square lattice) represented by a combination of units (for example, a unit cell) having a preferable structure.

  Note that the radial tilt alignment of the liquid crystal molecules 30a is counterclockwise or clockwise as shown in FIGS. 5B and 5C rather than the simple radial tilt alignment as shown in FIG. A spiral radial gradient orientation is more stable. In this spiral alignment, the alignment direction of the liquid crystal molecules 30a does not change spirally along the thickness direction of the liquid crystal layer 30 as in the normal twist alignment, but the alignment direction of the liquid crystal molecules 30a is seen in a minute region. And hardly changes along the thickness direction of the liquid crystal layer 30. That is, the cross-section at any position in the thickness direction of the liquid crystal layer 30 (the cross-section in a plane parallel to the layer surface) is in the same alignment state as FIG. 5B or 5C, and the thickness of the liquid crystal layer 30 Almost no twist deformation along the vertical direction occurs. However, a certain amount of twist deformation occurs in the entire liquid crystal domain.

  When a material in which a chiral agent is added to a nematic liquid crystal material having negative dielectric anisotropy is used, the liquid crystal molecules 30a center around the opening 14a and the unit solid portion 14b ′ when a voltage is applied, as shown in FIG. And take the counterclockwise or clockwise spiral gradient orientation shown in (c). Whether it is clockwise or counterclockwise depends on the type of chiral agent used. Therefore, when the voltage is applied, the liquid crystal layer 30 in the opening 14a is spirally inclined and oriented, so that the radially inclined liquid crystal molecules 30a are wound around the liquid crystal molecules 30a standing perpendicular to the substrate surface. Since the direction can be made constant in all liquid crystal domains, uniform display without roughness can be achieved. Furthermore, since the direction of winding around the liquid crystal molecules 30a standing perpendicular to the substrate surface is determined, the response speed when a voltage is applied to the liquid crystal layer 30 is also improved.

  When the chiral agent is added, the orientation of the liquid crystal molecules 30a changes spirally along the thickness direction of the liquid crystal layer 30 as in a normal twist orientation. In the alignment state in which the alignment of the liquid crystal molecules 30a does not change spirally along the thickness direction of the liquid crystal layer 30, the liquid crystal molecules 30a aligned in a direction perpendicular or parallel to the polarization axis of the polarizing plate are incident light. Therefore, the incident light passing through the region having such an alignment state does not contribute to the transmittance. On the other hand, in the alignment state in which the alignment of the liquid crystal molecules 30a changes spirally along the thickness direction of the liquid crystal layer 30, the liquid crystal molecules 30a aligned in the direction perpendicular or parallel to the polarization axis of the polarizing plate are also included. In addition to giving a phase difference to the incident light, the optical rotation of the light can be used. Accordingly, the incident light passing through the region having such an orientation also contributes to the transmittance, so that a liquid crystal display device capable of bright display can be obtained.

  FIG. 1A shows an example in which the opening 14a has a substantially star shape, the unit solid portion 14b ′ has a substantially circular shape, and these are arranged in a square lattice shape. The shape of the unit solid portion 14b ′ and the arrangement thereof are not limited to the above example.

  FIGS. 6A and 6B are top views of pixel electrodes 14A and 14B having openings 14a and unit solid portions 14b 'having different shapes, respectively.

  The openings 14a and unit solid portions 14b ′ of the pixel electrodes 14A and 14B shown in FIGS. 6A and 6B are respectively the openings 14a of the pixel electrodes shown in FIG. The real part 14b 'has a slightly distorted shape. The openings 14a and unit solid portions 14b ′ of the pixel electrodes 14A and 14B have a 2-fold rotation axis (no 4-fold rotation axis), and are regularly arranged to form a rectangular unit cell. ing. Each of the openings 14a has a distorted star shape, and each of the unit solid portions 14b 'has a substantially elliptical shape (distorted circle). Even when the pixel electrodes 14A and 14B are used, a liquid crystal display device having high display quality and excellent viewing angle characteristics can be obtained.

  Further, pixel electrodes 14C and 14D as shown in FIGS. 7A and 7B can be used.

  The pixel electrodes 14C and 14D have substantially cross-shaped openings 14a arranged in a square lattice so that the unit solid portions 14b 'are substantially square. Of course, these may be distorted to form a rectangular unit cell. Thus, even when the unit solid portions 14b ′ of a substantially rectangular shape (a rectangle includes a square and a rectangle) are regularly arranged, a liquid crystal display device with high display quality and excellent viewing angle characteristics can be obtained. .

  However, from the viewpoint of stabilizing the radial tilt orientation, the shape of the opening 14a and / or the unit solid portion 14b 'is preferably a substantially circular shape or a substantially elliptical shape rather than a substantially rectangular shape. It is preferable because the radial tilt alignment can be stabilized. When the shape of the opening 14a and / or the unit solid part 14b ′ is substantially circular or substantially elliptical, the side of the opening 14a (side of the unit solid part 14B ′) changes continuously (smoothly). This is because the orientation direction of the liquid crystal molecules 30a also changes continuously (smoothly).

  On the other hand, from the viewpoint of realizing bright display, the shape of the unit solid portion 14b 'is preferably close to a substantially rectangular shape. If the shape of the unit solid portion 14b ′ is substantially rectangular, the area ratio of the solid portion 14b in the pixel region can be increased, and the liquid crystal layer directly affected by the electric field generated by the electrode can be used. This is because the effective aperture ratio can be improved because the area can be increased.

  From the viewpoint of the continuity of the alignment direction of the liquid crystal molecules 30a described above, the pixel electrodes 14E and 14F shown in FIGS. 8A and 8B are also conceivable. A picture element electrode 14E shown in FIG. 8A is a modification of the picture element electrode 14 shown in FIG. 1A, and has an opening 14a composed of only four arcs. The pixel electrode 14F shown in FIG. 8B is a modification of the pixel electrode 14D shown in FIG. 7B, and the unit solid portion 14b ′ side of the opening 14a is formed by an arc. . Each of the openings 14a and unit solid portions 14b ′ of the pixel electrodes 14E and 14F has a four-fold rotation axis and is arranged in a square lattice pattern (having a four-turn rotation axis). 6 (a) and 6 (b), the shape of the unit solid portion 14b ′ of the opening 14a is distorted into a shape having a two-fold rotation axis, and a rectangular lattice (two-fold rotation axis). May be formed.

  In the above-described example, the substantially star-shaped or substantially cross-shaped opening 14a is formed, and the shape of the unit solid portion 14b ′ is approximately circular, approximately elliptical, approximately square (rectangular), and approximately rectangular with rounded corners. Explained the configuration. On the other hand, the relationship between the opening portion 14a and the unit solid portion 14b 'may be negative / positive inverted. For example, FIG. 9 shows a pixel electrode 14G having a pattern in which the opening 14a and the unit solid portion 14b of the pixel electrode 14 shown in FIG. As described above, the pixel electrode 14G having a negative-positive inverted pattern has substantially the same function as the pixel electrode 14 shown in FIG. When the opening 14a and the unit solid portion 14b ′ are both substantially square like the pixel electrodes 14H and 14I shown in FIGS. 10A and 10B, respectively, negative / positive inversion may be performed. Some of them have the same pattern as the original pattern.

  Even when the pattern shown in FIG. 1A is negative-positive-inverted like the pattern shown in FIG. 9, the unit solid part 14b ′ having rotational symmetry at the edge part of the pixel electrode 14 It is preferable to form a part (about one-half or about one-fourth) of the opening 14a so that is formed. By adopting such a pattern, the effect of the oblique electric field can be obtained at the edge portion of the pixel region similarly to the central portion of the pixel region, and a stable radial tilt orientation can be obtained over the entire pixel region. Can be realized.

  Next, the pixel electrode shown in FIG. 9 having a pattern obtained by negative-positive inversion of the pattern of the pixel electrode 14 of FIG. 1A and the opening 14a and unit solid portion 14b ′ of the pixel electrode 14 is shown. 14G is taken as an example to explain which negative / positive pattern should be adopted.

  Regardless of the negative-positive pattern, the length of the side of the opening 14a is the same for both patterns. Therefore, there is no difference between these patterns in the function of generating an oblique electric field. However, the area ratio of the unit solid portion 14b '(ratio to the total area of the pixel electrode 14) may be different between the two. That is, the area of the solid portion 14b (the portion where the conductive film actually exists) that generates the electric field used for the liquid crystal molecules of the liquid crystal layer may be different.

  Since the voltage applied to the liquid crystal domain formed in the opening 14a is lower than the voltage applied to the liquid crystal domain formed in the solid part 14b, for example, when a normally black mode display is performed, the opening The liquid crystal domain formed in the portion 14a becomes dark. That is, as the area ratio of the opening 14a increases, the display luminance tends to decrease. Therefore, it is preferable that the area ratio of the solid portion 14b is high.

  Whether the area ratio of the solid portion 14b is higher in the pattern of FIG. 1A or the pattern of FIG. 9 depends on the pitch (size) of the unit cell.

  11A shows a unit cell having the pattern shown in FIG. 1A, and FIG. 11B shows a unit cell having the pattern shown in FIG. 9 (provided that the opening 14a is the center). Is shown. In FIG. 11B, the portion (branch portion extending in all directions from the circular portion) that plays the role of connecting the unit solid portions 14b 'in FIG. 9 is omitted. Let p be the length (pitch) of one side of the square unit cell, and s be the length (space on one side) of the gap between the opening 14a or unit solid portion 14b 'and the unit cell.

  Various pixel electrodes 14 having different values of the pitch p and the one-side space s were formed, and the stability of the radial tilt alignment was examined. As a result, first, an oblique electric field necessary for obtaining a radial gradient orientation is generated using the picture element electrode 14 having the pattern shown in FIG. 11A (hereinafter referred to as “positive pattern”). For this purpose, it has been found that the space s on one side is required to be about 2.75 μm or more. On the other hand, for the pixel electrode 14 having the pattern shown in FIG. 11B (hereinafter referred to as a “negative pattern”), a one-side space s is formed to generate an oblique electric field for obtaining a radially inclined alignment. It was found that about 2.25 μm or more is necessary. The space ratio of the solid portion 14b when the value of the pitch p was changed was examined using the one-side space s as the lower limit value. The results are shown in Table 1 and FIG.

  As can be seen from Table 1 and FIG. 11 (c), when the pitch p is about 25 μm or more, the positive type (FIG. 11 (a)) pattern has a higher area ratio of the solid portion 14b and is shorter than about 25 μm. As a result, the area ratio of the solid portion 14b is larger in the negative type (FIG. 11B). Therefore, from the viewpoint of display brightness and orientation stability, the pattern to be adopted changes with the pitch p of about 25 μm as a boundary. For example, when three or less unit cells are provided in the width direction of the pixel electrode 14 having a width of 75 μm, the positive pattern shown in FIG. 11A is preferable, and when four or more unit cells are provided. Is preferably the negative pattern shown in FIG. In cases other than the illustrated pattern, either a positive type or a negative type may be selected so that the area ratio of the solid portion 14b is increased.

  The number of unit cells is obtained as follows. The size of the unit cell is calculated so that one or two or more integer unit cells are arranged with respect to the width (horizontal or vertical) of the picture element electrode 14, and the solid part is obtained for each unit cell size. Calculate the area ratio and select the unit cell size that maximizes the solid area ratio. However, when the diameter of the unit solid portion 14b ′ is less than 15 μm in the case of a positive pattern, and when the diameter of the opening 14a is less than 15 μm in the case of a negative pattern, the alignment regulating force due to the oblique electric field is reduced and stable. It is difficult to obtain a radially inclined orientation. The lower limit of these diameters is when the thickness of the liquid crystal layer 30 is about 3 μm. When the thickness of the liquid crystal layer 30 is thinner than this, the diameters of the unit solid portion 14b ′ and the opening 14a are A stable radial tilt alignment can be obtained even if it is smaller than the above lower limit, and the unit solid portion 14b ′ and the solid solid tilt alignment 14b ′ necessary for obtaining a stable radial tilt alignment when the thickness of the liquid crystal layer 30 is thicker than this. The lower limit value of the diameter of the opening 14a is larger than the above lower limit value.

  As will be described later, by forming a convex portion inside the opening 14a or forming a convex portion on the counter substrate 100b, it is possible to improve the stability of the radial inclined alignment. All of the above-mentioned conditions are for the case where no protrusion is formed.

  Next, with reference to FIGS. 12A and 12B, the configuration of the liquid crystal display device 100 according to the present invention will be described in more detail. FIG. 12A shows the pixel electrode 14 whose outer shape is defined so as not to have an opening but to have three unit solid portions 14 b ′.

  As shown in FIGS. 12A and 12B, the TFT substrate 100a includes a pixel electrode 14 provided for each pixel region, and a thin film transistor (not shown here) electrically connected to the pixel electrode 14. And a scanning wiring 2 and a signal wiring 4 electrically connected to the thin film transistor. The TFT substrate 100a further includes an auxiliary capacitance line 6 and an auxiliary capacitance electrode 8 facing the auxiliary capacitance line 6 and electrically connected to the drain electrode of the thin film transistor.

  A first insulating layer (first interlayer insulating film) 3 is provided between the auxiliary capacitance line 6 and the auxiliary capacitance electrode 8 as shown in FIG. Further, a second insulating layer (second interlayer insulating film) 7 is provided so as to cover the wiring and the thin film transistor described above, and the pixel electrode 14 is formed on the second insulating layer 7.

  The pixel electrode 14, the counter electrode 22, and the liquid crystal layer 30 constitute a “liquid crystal capacitance”, whereas the auxiliary capacitance wiring 6, the auxiliary capacitance electrode 8, and the first insulating layer 3 constitute an “auxiliary capacitance” ( Also called “storage capacity”). That is, the liquid crystal display device 100 includes a pixel capacitor 40 electrically connected to each of the plurality of thin film transistors 50 as shown in an equivalent circuit in FIG. And an auxiliary capacitor 44 electrically connected in parallel to the liquid crystal capacitor 42. If the picture element capacitor 40 is composed only of the liquid crystal capacitor 42, the voltage decreases due to the leakage current of the liquid crystal capacitor 42. Therefore, an auxiliary capacitor 44 is provided to suppress and prevent this.

  The auxiliary capacity wiring 6 and the auxiliary capacity electrode 8 constituting the auxiliary capacity 44 are typically formed from a light-shielding material. In the present embodiment, the auxiliary capacitor wiring 6 patterns the same metal layer as the gate electrode G of the thin film transistor 50 and the scanning wiring 2 (for example, a single layer of Al, Ta, W, ITO, or a single layer or a laminate of these compounds). Formed by. The auxiliary capacitor electrode 8 is formed by patterning the same metal layer as the source electrode S, drain electrode D, and signal wiring 4 of the thin film transistor 50 (for example, a single layer or a laminate of Al, Ta, W, ITO, or a compound thereof). It is formed by doing.

The first insulating layer 3 is typically a gate insulating film (eg, SiN layer, SiO ₂ layer) formed on almost the entire surface of the TFT substrate 100a so as to cover the gate electrode G and the scanning wiring 2 of the thin film transistor 50. It is a part. In the present embodiment, the second insulating layer 7 is a film made of a resin material (for example, having a thickness of 2) so as to cover the source electrode S, the drain electrode G, the signal wiring 4 and the auxiliary capacitance electrode 8 of the thin film transistor 50. 0.5 μm to 3.2 μm resin film).

  As shown in FIGS. 12A and 12B, the auxiliary capacitance wiring 6, the auxiliary capacitance electrode 8, and the first insulating layer 3 are all located between the two unit solid portions 14b ′. It is provided as follows. That is, in the liquid crystal display device 100 according to the present invention, most of the auxiliary capacitor 44 is formed in a region where the solid portion 14b is not provided in the pixel region (the conductive film of the pixel electrode 14 is formed on the TFT substrate 100a). Is not located in the area. Therefore, it is possible to suppress a decrease in effective aperture ratio (transmittance) caused by the auxiliary capacitor 44 that typically includes a light-shielding member, and to increase the area of the solid portion 14b that contributes to display. it can. Therefore, bright display is realized.

  The effect that the effective aperture ratio is improved by the above-described configuration is an effect that can be obtained specifically for a liquid crystal display device having an electrode structure for realizing radial tilt alignment. In the electrode structure that realizes the radial inclined orientation, as described with reference to FIGS. 1 to 11, the opening 14 a is formed in the pixel electrode 14, or the pixel electrode 14 has a plurality of unit solid portions 14 b ′. This is because the outer shape of the pixel electrode 14 is defined so as to have a solid region 14b (conductive film) in the pixel region. On the other hand, in a general liquid crystal display device (for example, a TN type liquid crystal display device), the picture element electrode has almost the same shape as the picture element region (typically, a substantially rectangular shape), and the position of the auxiliary capacitor is shown in the picture. Even if it is changed within the elementary region, the effect of improving the aperture ratio cannot be obtained. Rather, in such a liquid crystal display device, the auxiliary capacitance is configured by overlapping the auxiliary capacitance wiring with a part of the pixel electrode through the insulating film.

  In the present embodiment, the TFT substrate 100 a has the second insulating layer 7 that covers the thin film transistor 50 and the auxiliary capacitance electrode 8, and the pixel electrode 14 is formed on the second insulating layer 7. Since it is employed, the pixel electrode 14 can be provided so as to partially overlap the thin film transistor 50, the scanning wiring 2, the signal wiring 4, and the like, and the aperture ratio can be further improved.

  In order to generate an oblique electric field having a sufficient strength to obtain a radially inclined alignment, it is preferable that the second insulating layer 7 be a thick film. The auxiliary capacitance electrode 8 constituting the auxiliary capacitance 44 is electrically connected to the drain electrode G of the thin film transistor 50, and has substantially the same potential as the solid portion 14b of the pixel electrode 14. Therefore, if a part of the auxiliary capacitance electrode 8 is located in a region where the solid portion 14b is not provided, the equipotential line EQ generated when the voltage is applied is sufficient in the region where the solid portion 14b is not provided. In some cases, an oblique electric field having a sufficient strength may not be generated around the unit solid portion 14b ′.

  If the second insulating layer 7 is made thick, the voltage drop due to the second insulating layer 7 can be made sufficiently large, and the equipotential line EQ can be sufficiently lowered in a region where the solid portion 14b is not provided. An oblique electric field having a sufficient strength can be generated around the unit solid portion 14b ′. Further, since the surface of the second insulating layer 7 on the liquid crystal layer 3 side can be substantially flattened by making the second insulating layer 7 thick, the pixel electrode formed thereon 14 can be prevented from generating a step in the solid portion 14b.

  On the other hand, as shown in FIG. 14A, when the second insulating layer 7 is a thin film (for example, a thin film made of an inorganic material), an oblique electric field having a sufficient strength is generated around the solid portion 14b. It may not be generated. In this case, a step reflecting the thickness of the auxiliary capacitor 44 is generated on the surface of the second insulating layer 7 on the liquid crystal layer 30 side, and a step is also generated in the solid portion 14b of the pixel electrode 14. May end up. As shown in FIG. 14 (b), it is also possible to increase the slant of sufficient strength by widening the interval between the unit solid portions 14b ′ so that the auxiliary capacitor 44 and the solid portion 14b do not substantially overlap. Although an electric field can be formed, with such a configuration, since the area ratio of the solid portion 14b is eventually reduced, the effect of improving the effective aperture ratio cannot be sufficiently obtained.

  In order to obtain a sufficiently stable radial gradient orientation, the thickness of the second insulating layer 7 is specifically preferably 1 μm or more, and more preferably 2.5 μm or more. Further, when the second insulating layer 7 is formed from a resin material (for example, a transparent resin material having photosensitivity such as acrylic resin), it is easy to increase the thickness of the second insulating layer 7.

  12A and 12B exemplify a case where most of the auxiliary capacitor 44 is located in a region where the solid portion 14b is not provided, the present invention is limited to this. Instead, at least a part of the auxiliary capacitor 44 is located in a region where the solid portion 14b is not provided, so that an effect of improving the aperture ratio can be obtained. However, from the viewpoint of sufficiently improving the aperture ratio, it is preferable that as many portions of the auxiliary capacitor 44 are located in a region where the solid portion 14b is not provided. Specifically, it is preferable that ¼ or more of the auxiliary capacity 44 is located in an area where the solid portion 14b is not provided, more preferably ½ or more, and almost all. It is more preferable that the part of is located.

  Since the capacitance value required for the auxiliary capacitor 44 varies depending on the specifications of the liquid crystal display device, it may be difficult to design all the portions of the auxiliary capacitor 44 in an area where the solid portion 14b is not provided. In that case, the auxiliary capacitor 44 may be appropriately overlapped with the solid portion 14b as necessary. In order to obtain a desired capacitance value, the width of the auxiliary capacitance line 6 or the auxiliary capacitance electrode 8 may be simply increased. However, by forming a branch structure in the auxiliary capacitance line 6 or the auxiliary capacitance electrode 8, Design with a high degree of freedom is possible with respect to the arrangement of the auxiliary capacitor 44 in the region, and a sufficient effective aperture ratio can be obtained while ensuring a sufficient capacitance value.

  FIGS. 15A and 15B schematically show a liquid crystal display device 200 in which a branch structure is formed in the auxiliary capacitance line 6 and the auxiliary capacitance electrode 8.

  As shown in FIGS. 15A and 15B, the auxiliary capacitance wiring 6 has a wiring trunk 6a extending substantially parallel to the scanning wiring 2, and a wiring branch 6b extending from the wiring trunk 6a. Yes. Further, the auxiliary capacitance electrode 8 has an electrode trunk 8a facing the wiring trunk 6a via the first insulating layer, and an electrode branch 8b extending from the electrode trunk 8a.

  The stripe-shaped wiring trunk 6 a and the strip-shaped electrode trunk 8 a face each other with the first insulating layer 3 interposed therebetween, and constitute a part of the auxiliary capacitor 44. Further, the wiring branch portion 6 b and the electrode branch portion 8 b are also opposed to each other via the first insulating layer 3 and constitute a part of the auxiliary capacitor 44. In the present embodiment, the wiring branch part 6b and the electrode branch part 8b are extended so as to overlap with the vicinity of the center of the unit solid part 14b '.

  Typically, a contact hole is formed in the second insulating layer 7 on the electrode branch portion 8b, and the pixel electrode 14 and the electrode branch portion 8b are connected within the contact hole. That is, the pixel electrode 14 is electrically connected to the drain electrode of the thin film transistor via the electrode branch portion 8b (auxiliary capacitance electrode 8).

  In the liquid crystal display device 200, as shown in FIGS. 15A and 15B, a part of the auxiliary capacitor 44, more specifically, the wiring trunk 6a and the electrode trunk 8a and the first located between them. Most of the capacitance formed by the insulating layer 3 is located in a region where the solid portion 14b is not provided. Therefore, the effect of improving the aperture ratio can be obtained as in the liquid crystal display device 100.

  Further, in the liquid crystal display device 200, a contact portion is formed in the solid portion 14 b of the pixel electrode 14 by forming a branch structure in the auxiliary capacitance electrode 8, and a branch structure is also formed in the auxiliary capacitance wiring 6. A capacitance (configured by the wiring branch portion 6b and the electrode branch portion 8b and the first insulating layer 3 therebetween) that overlaps the solid portion 14b is formed. In this way, a capacity overlapping the solid portion 14b may be formed as necessary.

  Next, still another liquid crystal display device 300 according to the present invention will be described with reference to FIG. Although the liquid crystal display device 300 is different from the liquid crystal display devices 100 and 200 in that the pixel electrode 14 has a plurality of openings 14a, the liquid crystal display device 300 develops an alignment regulating force for radial tilt alignment. There is no difference in point.

  The auxiliary capacity wiring 6 of the liquid crystal display device 300 has two wiring trunks 6a as shown in FIG. The auxiliary capacitance wiring 6 further extends from the wiring trunk 6a and further includes a wiring branch 6b that connects the wiring trunks 6a. The overall shape of the auxiliary capacitance wiring 6 is a ladder shape.

  Further, as shown in FIG. 16, the auxiliary capacitance electrode 8 of the liquid crystal display device 300 has two electrode trunk portions 8a each facing the wiring trunk portion 6a. The auxiliary capacitance electrode 8 further includes an electrode branch portion 8b extending from the electrode trunk portion 8a and connecting the electrode trunk portions 8a to each other, and the entire shape of the auxiliary capacitance electrode 8 is an E shape (H shape). .

  Also in the liquid crystal display device 300, a part of the auxiliary capacitance is located in a region where the solid portion 14b is not provided, and the auxiliary capacitance wiring 6 and the auxiliary capacitance electrode 8 are respectively connected to the wiring branch portion 6b and the electrode branch portion 8b. Therefore, the same effect as the liquid crystal display device 100 or the liquid crystal display device 200 can be obtained.

  Further, since the auxiliary capacitance wiring 6 has a plurality of wiring trunks 6a and the auxiliary capacitance electrode 8 has a plurality of electrode trunks 8a, the width of each of the wiring trunks 6a and the width of each of the electrode trunks 8a are narrowed. Therefore, most of the auxiliary capacitance constituted by the wiring trunk 6a and the electrode trunk 8a (and the first insulating layer located between them) is not provided with the solid portion 14b. It becomes possible to be located within the region. In this way, by forming the plurality of wiring trunks 6 a in the auxiliary capacitance wiring 6 and forming the plurality of electrode trunks 8 a in the auxiliary capacitance electrode 8, the degree of freedom of design is further increased, and more of the auxiliary capacitance 44 is increased. Since the portion can be positioned in a region where the solid portion 14b is not provided, a design with a higher aperture ratio can be realized.

  Next, the alignment control structure provided on the counter substrate will be described with reference to FIGS. FIGS. 17A to 17D are views schematically showing the counter substrate 400b having the alignment regulating structure 28. FIG. 17A to 17D has an alignment regulating force on the liquid crystal molecules of the liquid crystal layer 30 in a state where a voltage is applied at least between the pixel electrode 14 and the counter electrode 22. And acts so that the liquid crystal molecules 30a of the liquid crystal layer 30 are radially inclined and aligned. The orientation regulation direction by the orientation regulation structure 28 matches the orientation regulation direction by the oblique electric field generated around the unit solid portion 14b '.

  The alignment regulating structure 28 shown in FIG. 17A is configured by the opening 22 a of the counter electrode 22. Note that a vertical alignment film (not shown) is provided on the surface of the counter substrate 300b on the liquid crystal layer 30 side.

  The orientation regulating structure 28 exhibits an orientation regulating force only when a voltage is applied. Since the alignment regulating structure 28 only needs to exert an alignment regulating force on the liquid crystal molecules in the liquid crystal domain formed by the solid portion 14 b of the pixel electrode 14, the size of the opening 22 a is determined by the size of the pixel electrode 14. Is smaller than the opening 14a provided in the unit, and smaller than the unit solid part 14b ′ (see, for example, FIG. 1A). For example, sufficient effects can be obtained when the area of the opening 14a or the unit solid portion 14b 'is less than half of the area. By providing the opening 22a of the counter electrode 22 at a position facing the central portion of the unit solid portion 14b ′ of the pixel electrode 14, the continuity of alignment of liquid crystal molecules is increased, and the central axis of the radially inclined alignment is obtained. The position of can be fixed.

  As described above, when a structure that exhibits an alignment regulating force only when a voltage is applied is adopted as the alignment regulating structure, almost all liquid crystal molecules 30a of the liquid crystal layer 30 take a vertical alignment state when no voltage is applied. When the mode is adopted, light leakage hardly occurs in the black display state, and a display with a good contrast ratio can be realized.

  However, since no alignment regulating force is generated in the state where no voltage is applied, a radially inclined alignment is not formed, and when the applied voltage is low, the orientation regulating force is small, so if an excessively large stress is applied to the liquid crystal panel, an afterimage is formed. It may be visually recognized.

  The alignment regulating structure 28 shown in FIGS. 17 (b) to 17 (d) exhibits an alignment regulating force regardless of whether a voltage is applied or not, so that a stable radial gradient orientation is obtained in all display gradations. Excellent resistance to stress.

  First, the alignment regulating structure 28 shown in FIG. 17B has a convex portion 22 b that protrudes toward the liquid crystal layer 30 on the counter electrode 22. Although there is no restriction | limiting in particular in the material which forms the convex part 22b, It can form easily using dielectric materials, such as resin. Note that a vertical alignment film (not shown) is provided on the surface of the counter substrate 400b on the liquid crystal layer 30 side. The convex portion 22b causes the liquid crystal molecules 30a to be radially inclined and aligned by the shape effect of the surface (having vertical alignment). The convex portions 22b shown in FIGS. 15A and 16 also have the same function. In addition, it is preferable to use a resin material that is deformed by heat because a convex portion 22b having a gentle cross-sectional shape as shown in FIG. 17B can be easily formed by heat treatment after patterning. As shown in the drawing, the convex portion 22b having a gentle cross-sectional shape having a vertex (for example, a part of a sphere) or the convex portion having a conical shape is excellent in the effect of fixing the center position of the radial inclined orientation.

  The alignment regulating structure 28 shown in FIG. 17C has a liquid crystal layer 30 side in an opening 23 (which may be a recess) provided in a dielectric layer 23 formed under the counter electrode 22 (on the substrate 21 side). It is comprised by the horizontal orientation surface. Here, the vertical alignment film 24 formed on the liquid crystal layer 30 side of the counter substrate 400b is not formed only in the opening 23a, so that the surface in the opening 23a is a horizontal alignment surface. Instead, as shown in FIG. 17D, the horizontal alignment film 25 may be formed only in the opening 23a.

  In the horizontal alignment film shown in FIG. 17D, for example, the vertical alignment film 24 is once formed on the entire surface of the counter substrate 200b, and the vertical alignment film 24 existing in the opening 23a is selectively irradiated with ultraviolet rays. Then, it may be formed by reducing the vertical alignment. The horizontal alignment necessary for constituting the alignment regulating structure 28 does not need to have a small pretilt angle as in an alignment film used in a TN liquid crystal display device. For example, if the pretilt angle is 45 ° or less. Good.

  As shown in FIGS. 17C and 17D, the liquid crystal molecules 30a are intended to be aligned horizontally with respect to the substrate surface on the horizontal alignment surface in the opening 23a. An orientation that maintains continuity with the orientation of the vertically aligned liquid crystal molecules 30a is formed, and a radially inclined orientation as shown is obtained.

  Without providing a recess (formed by the opening of the dielectric layer 23) on the surface of the counter electrode 22, a horizontal orientation surface (the surface of the electrode or a horizontal alignment film) is formed on the flat surface of the counter electrode 22. Although the radial tilt alignment can be obtained only by selective provision, the radial tilt alignment can be further stabilized by the shape effect of the recesses.

  In order to form a recess on the surface of the counter substrate 400b on the liquid crystal layer 30 side, for example, a color filter layer or an overcoat layer of a color filter layer is preferably used as the dielectric layer 23 because the process does not increase. . In addition, the structure shown in FIGS. 17C and 17D does not have a region where a voltage is applied to the liquid crystal layer 30 via the convex portion 22b unlike the structure shown in FIG. There is little decrease in light utilization efficiency.

  FIG. 18A shows a cross-sectional configuration of a liquid crystal display device 400 provided with the alignment regulating structure 28 described above. In FIG. 18A, the auxiliary capacitor of the TFT substrate 100a is omitted.

  The liquid crystal display device 400 includes a TFT substrate 100 a having the picture element electrode 14 including the solid portion 14 b and a counter substrate 400 b having the alignment regulating structure 28. Here, as the alignment regulating structure 28, one that exhibits the alignment regulating force even when no voltage is applied (FIGS. 17B to 17D) is illustrated, but the one shown in FIG. 17A may be used. it can. Further, the TFT substrate 100a shown in FIG. 18A may be the TFT substrate 200a shown in FIG.

  The alignment regulating structure 28 provided on the counter substrate 400b is disposed corresponding to a region corresponding to the unit solid portion 14b ′ of the pixel electrode 14, more specifically, near the center of the unit solid portion 14b ′. Yes. By arranging in this way, in a state in which a voltage is applied to the liquid crystal layer 30, that is, in a state in which a voltage is applied between the pixel electrode 14 and the counter electrode 22, an oblique generated around the solid portion 14b. The alignment regulation direction by the electric field and the alignment regulation direction by the alignment regulation force developed by the alignment regulation structure 28 are matched, and the radial tilt alignment is stabilized. This is schematically shown in FIGS. 18 (a) to 18 (c). FIG. 18A shows a state in which no voltage is applied, FIG. 18B shows a state in which the orientation starts to change after voltage application (ON initial state), and FIG. 18C shows a steady state during voltage application. This is shown schematically.

  As shown in FIG. 18A, the alignment regulating force due to the alignment regulating structure (FIGS. 17B to 17D) acts on the liquid crystal molecules 30a in the vicinity even when no voltage is applied, thereby causing radial tilt alignment. Form.

  When the voltage starts to be applied, an electric field indicated by the equipotential line EQ as shown in FIG. 18B is generated (by the solid portion 14b), and the liquid crystal is formed in a region corresponding to the opening 14a and the solid portion 14b. A liquid crystal domain in which the molecules 30a are radially inclined is formed, and reaches a steady state as shown in FIG. At this time, the tilt direction of the liquid crystal molecules 30a in each liquid crystal domain coincides with the tilt direction of the liquid crystal molecules 30a due to the alignment regulating force of the alignment regulating structure 28 provided in the corresponding region.

  Thus, by providing the alignment regulating structure 28 on the counter substrate 400b, the radially inclined alignment state formed by the picture element electrodes 14 can be further stabilized, which is caused by the application of stress to the liquid crystal cell. Decrease in display quality can be suppressed.

  When a stress is applied to the liquid crystal display device 400 in a steady state, the radial tilt alignment of the liquid crystal layer 30 is temporarily lost. However, when the stress is removed, the alignment regulating force by the pixel electrode 14 and the alignment regulating structure 28 is increased by the liquid crystal molecules. Since it acts on 30a, it returns to a radially inclined alignment state. Therefore, the occurrence of afterimages due to stress is suppressed. If the alignment regulating force by the alignment regulating structure 28 is too strong, retardation due to radial tilt alignment may occur even when no voltage is applied, and the contrast ratio of the display may be reduced. Since it is only necessary to stabilize the radial tilt alignment formed by the elementary electrode 14 and to fix the center axis position, strong alignment control force is not required, and the alignment does not generate retardation that degrades the display quality. Regulatory power is sufficient.

  For example, when the convex portion 22b shown in FIG. 17 (b) is employed, the unit solid portion 14b ′ having a diameter of about 30 μm to about 35 μm has a diameter of about 15 μm and a height (thickness) of about 30 μm. If the 1 μm convex portion 22 is formed, a sufficient alignment regulating force can be obtained, and a decrease in contrast ratio due to retardation can be suppressed to a level that causes no problem in practice.

  Up to this point, the alignment control structure provided on the counter substrate has been described. However, instead of the above-described alignment control structure, or together with the above-described alignment control structure, a convex portion is provided on the TFT substrate, thereby causing the radial inclined alignment. May be stabilized.

  With reference to FIGS. 19A and 19B, the structure of the liquid crystal display device 500 having the protrusions 60 on the TFT substrate 500a will be described. FIG. 19A is a top view seen from the normal direction of the substrate, and FIG. 19B corresponds to a cross-sectional view taken along the line 19B-19B ′ in FIG. FIG. 19B shows a state where no voltage is applied to the liquid crystal layer. 19 (a) and 19 (b), the auxiliary capacitor is not shown, but also in the liquid crystal display device 500, at least a part of the auxiliary capacitor is solid as in the liquid crystal display devices 100, 200, and 300. It is provided so that it may be located in the area | region where the part 14b is not provided.

  As shown in FIGS. 19A and 19B, the liquid crystal display device 500 has the above-described liquid crystal display device in that the TFT substrate 500a has a convex portion 60 inside the opening portion 14a of the pixel electrode 14. Is different. A vertical alignment film (not shown) is provided on the surface of the convex portion 60.

  The cross-sectional shape of the convex portion 60 in the in-plane direction of the substrate 11 is the same as the shape of the opening 14a, as shown in FIG. However, the adjacent convex portions 60 are connected to each other, and are formed so as to completely surround the unit solid portion 14b 'in a substantially circular shape. The cross-sectional shape of the convex portion 60 in the in-plane direction perpendicular to the substrate 11 is a trapezoid as shown in FIG. That is, it has a top surface 60t parallel to the substrate surface and a side surface 60s inclined at a taper angle θ (<90 °) with respect to the substrate surface. Since a vertical alignment film (not shown) is formed so as to cover the convex portion 60, the side surface 60s of the convex portion 60 is in the same direction as the alignment regulating direction by the oblique electric field with respect to the liquid crystal molecules 30a of the liquid crystal layer 30. It will have an orientation regulating force and will act to stabilize the radial tilt orientation.

  The operation of the convex portion 60 will be described with reference to FIGS. 20 (a) to 20 (d) and FIGS. 21 (a) and 21 (b).

  First, the relationship between the alignment of the liquid crystal molecules 30a and the shape of the surface having vertical alignment will be described with reference to FIGS.

  As shown in FIG. 20A, the liquid crystal molecules 30a on the horizontal surface are perpendicular to the surface by the alignment regulating force of the surface having vertical alignment (typically, the surface of the vertical alignment film). Oriented to When an electric field represented by an equipotential line EQ perpendicular to the axial direction of the liquid crystal molecules 30a is applied to the liquid crystal molecules 30a in the vertical alignment state in this way, the liquid crystal molecules 30a are rotated clockwise or counterclockwise. The torque to be tilted is applied with the same probability. Accordingly, in the liquid crystal layer 30 between the electrodes of the parallel plate type arrangement facing each other, the liquid crystal molecules 30a receiving the torque in the clockwise direction and the liquid crystal molecules 30a receiving the torque in the counterclockwise direction are mixed. As a result, the transition to the alignment state according to the voltage applied to the liquid crystal layer 30 may not occur smoothly.

  As shown in FIG. 20B, when an electric field represented by a horizontal equipotential line EQ is applied to the liquid crystal molecules 30a aligned perpendicular to the inclined surface, the liquid crystal molecules 30a. Is inclined in a direction (clockwise in the illustrated example) with a small amount of inclination for being parallel to the equipotential line EQ. Further, as shown in FIG. 20C, the liquid crystal molecules 30a aligned perpendicular to the horizontal surface are continuously aligned with the liquid crystal molecules 30a aligned perpendicular to the inclined surface. In such a manner (so as to be aligned), the liquid crystal molecules 30a located on the inclined surface are inclined in the same direction (clockwise).

  As shown in FIG. 20 (d), with respect to a continuous uneven surface having a trapezoidal cross section, the top surface is aligned with the alignment direction regulated by the liquid crystal molecules 30a on each inclined surface. And the liquid crystal molecules 30a on the bottom surface are aligned.

  The liquid crystal display device according to the present embodiment stabilizes the radial tilt alignment by matching the orientation regulating force direction due to such a surface shape (convex portion) with the orientation regulating direction due to the oblique electric field.

  FIGS. 21A and 21B show a state in which a voltage is applied to the liquid crystal layer 30 shown in FIG. 19B, respectively, and FIG. 21A shows the voltage applied to the liquid crystal layer 30. Accordingly, the state in which the orientation of the liquid crystal molecules 30a starts to change (ON initial state) is schematically shown, and FIG. 21B shows that the orientation of the liquid crystal molecules 30a changed according to the applied voltage is steady. The state which reached the state is shown typically. A curve EQ in FIGS. 21A and 21B shows an equipotential line EQ.

  When the pixel electrode 14 and the counter electrode 22 are at the same potential (a state where no voltage is applied to the liquid crystal layer 30), as shown in FIG. 19B, the liquid crystal molecules 30a in the pixel region are , Oriented perpendicular to the surfaces of both substrates 11 and 21. At this time, the liquid crystal molecules 30a in contact with the vertical alignment film (not shown) on the side surface 60s of the protrusion 60 are aligned perpendicular to the side surface 60s, and the liquid crystal molecules 30a in the vicinity of the side surface 60s are aligned with the peripheral liquid crystal molecules 30a. As shown in the figure, the slanted orientation is obtained by the interaction (the property as an elastic body).

  When a voltage is applied to the liquid crystal layer 30, a potential gradient represented by the equipotential line EQ shown in FIG. This equipotential line EQ is parallel to the surface of the solid portion 14b and the counter electrode 22 in the liquid crystal layer 30 located between the solid portion 14b of the picture element electrode 14 and the counter electrode 22, and It falls in a region corresponding to the opening 14a of the elementary electrode 14 and is inclined in the liquid crystal layer 30 on the edge portion of the opening 14a (the inner periphery of the opening 14a including the boundary (extended) of the opening 14a). An oblique electric field represented by an equipotential line EQ is formed.

  Due to this oblique electric field, as described above, the liquid crystal molecules 30a on the edge part EG are rotated clockwise in the right edge part EG in the figure as indicated by arrows in FIG. The left edge portion EG is tilted (rotated) in the counterclockwise direction and oriented parallel to the equipotential line EQ. The orientation regulating direction by the oblique electric field is the same as the orientation regulating direction by the side surface 60s located at each edge portion EG.

  As described above, when the change in alignment starting from the liquid crystal molecules 30a located on the inclined equipotential line EQ progresses and reaches a steady state, the alignment state schematically shown in FIG. The liquid crystal molecules 30a located in the vicinity of the center of the opening 14a, that is, in the vicinity of the center of the top surface 60t of the convex portion 60, have substantially the same influence on the orientation of the liquid crystal molecules 30a at the opposite edge portions EG of the opening 14a. Therefore, the liquid crystal molecules 30a in the region away from the center of the opening 14a (the top surface 60t of the convex portion 60) are kept perpendicular to the equipotential line EQ, and the liquid crystal molecules 30a in the regions near the edge portion EG The liquid crystal molecules 30a are tilted under the influence of the orientation of the liquid crystal molecules 30a, and form a tilted orientation that is symmetrical with respect to the center SA of the opening 14a (the top surface 60t of the convex portion 60). Further, in the region corresponding to the unit solid portion 14 b ′ substantially surrounded by the opening 14 a and the convex portion 60, a symmetric inclined orientation is formed with respect to the center SA of the unit solid portion 14 b ′.

  As described above, in the liquid crystal display device 500 as well, as in the liquid crystal display device 100, liquid crystal domains having a radially inclined alignment are formed corresponding to the openings 14 a and the unit solid portions 14 b ′. Since the convex portion 60 is formed so as to completely surround the unit solid portion 14 b ′ in a substantially circular shape, the liquid crystal domain is formed corresponding to the substantially circular region surrounded by the convex portion 60. Further, the side surface of the convex portion 60 provided inside the opening portion 14a acts to tilt the liquid crystal molecules 30a near the edge portion EG of the opening portion 14a in the same direction as the alignment direction by the oblique electric field. Stabilize the tilted orientation.

  Obviously, the alignment regulating force due to the oblique electric field acts only when a voltage is applied, and its strength depends on the strength of the electric field (the magnitude of the applied voltage). Therefore, when the electric field strength is weak (that is, the applied voltage is low), the alignment regulating force due to the oblique electric field is weak, and when an external force is applied to the liquid crystal panel, the radial gradient alignment may be disrupted by the flow of the liquid crystal material. Once the radial tilt alignment is broken, the radial tilt alignment is not restored unless a voltage sufficient to generate an oblique electric field that exhibits a sufficiently strong alignment regulating force is applied. On the other hand, the alignment regulating force by the side surface 60s of the convex portion 60 acts regardless of the applied voltage, and is very strong as known as the anchoring effect of the alignment film. Therefore, even if the liquid crystal material flows and the radial tilt alignment is broken, the liquid crystal molecules 30a in the vicinity of the side surface 60s of the convex portion 60 maintain the same alignment direction as that in the radial tilt alignment. Therefore, as long as the liquid crystal material stops flowing, the radial tilt alignment can be easily restored.

  As described above, the liquid crystal display device 500 has a feature of being strong against external force in addition to the feature of the liquid crystal display device 100. Therefore, the liquid crystal display device 500 is preferably used for a PC or PDA that is easily applied with an external force and frequently used in a portable manner.

  In addition, when the convex part 60 is formed using a highly transparent dielectric, there is an advantage that the contribution ratio to the display of the liquid crystal domain formed corresponding to the opening part 14a is improved. On the other hand, when the convex portion 60 is formed using an opaque dielectric, there is an advantage that light leakage due to the retardation of the liquid crystal molecules 30a tilted by the side surface 60s of the convex portion 60 can be prevented. Which is adopted may be determined according to the use of the liquid crystal display device. In any case, the use of the photosensitive resin has an advantage that the patterning process corresponding to the opening 14a can be simplified. In order to obtain a sufficient alignment regulating force, the height of the protrusion 60 is preferably in the range of about 0.5 μm to about 2 μm when the thickness of the liquid crystal layer 30 is about 3 μm. In general, the height of the convex portion 60 is preferably in the range of about 1/6 to about 2/3 of the thickness of the liquid crystal layer 30.

  As described above, the liquid crystal display device 500 has the convex portion 60 inside the opening portion 14 a of the pixel electrode 14, and the side surface 60 s of the convex portion 60 has an oblique electric field with respect to the liquid crystal molecules 30 a of the liquid crystal layer 30. It has an orientation regulating force in the same direction as the orientation regulating direction by. A preferable condition for the side surface 60s to have the alignment regulating force in the same direction as the alignment regulating direction by the oblique electric field will be described with reference to FIGS. 22 (a) to 22 (c).

  22A to 22C schematically show cross-sectional views of the liquid crystal display devices 500A, 500B, and 500C, respectively, and correspond to FIG. The liquid crystal display devices 500A, 500B, and 500C all have a convex portion inside the opening portion 14a, but the arrangement relationship between the entire convex portion 60 as one structure and the opening portion 14a is different from that of the liquid crystal display device 500. Yes.

  In the liquid crystal display device 500 described above, as shown in FIG. 21A, the entire convex portion 60 as a structure is formed inside the opening portion 14a, and the bottom surface of the convex portion 60 is open. It is smaller than the part 14a. In the liquid crystal display device 500A shown in FIG. 22A, the bottom surface of the convex portion 60A coincides with the opening portion 14a. In the liquid crystal display device 500B shown in FIG. The bottom surface is larger than the portion 14a and is formed so as to cover the solid portion (conductive film) 14b around the opening 14a. The solid portion 14b is not formed on any side surface 60s of the convex portions 60, 60A and 60B. As a result, as shown in each figure, the equipotential line EQ is substantially flat on the solid portion 14b and falls at the opening 14a as it is. Accordingly, the side surfaces 60s of the convex portions 60A and 60B of the liquid crystal display devices 500A and 500B exhibit the same orientation regulating force in the same direction as the alignment regulating force due to the oblique electric field, similar to the convex portion 60 of the liquid crystal display device 500 described above. Stabilize the radial tilt orientation.

  On the other hand, the bottom surface of the projection 60C of the liquid crystal display device 500C shown in FIG. 22C is larger than the opening 14a, and the solid portion 14b around the opening 14a is formed on the side surface 60s of the projection 60C. Has been. Due to the influence of the solid portion 14b formed on the side surface 60s, a peak is formed in the equipotential line EQ. The peak of the equipotential line EQ has a slope opposite to that of the equipotential line EQ that falls at the opening 14a, and this generates an oblique electric field that is opposite to the oblique electric field that causes the liquid crystal molecules 30a to be radially inclined and oriented. It shows that. Therefore, in order for the side surface 60s to have the alignment regulating force in the same direction as the alignment regulating direction by the oblique electric field, it is preferable that the solid part (conductive film) 14b is not formed on the side surface 60s.

  Next, a cross-sectional structure along the line 23A-23A 'of the convex portion 60 shown in FIG. 19A will be described with reference to FIG.

  As described above, the convex portion 60 shown in FIG. 19A is formed so as to completely surround the unit solid portion 14b ′ in a substantially circular shape, so that the unit solid portions 14b ′ adjacent to each other are adjacent to each other. The part (branch part from the circular part to the four sides) that plays the role of connecting to is formed on the convex part 60 as shown in FIG. Therefore, in the step of depositing the conductive film that forms the solid portion 14b of the pixel electrode 14, there is a high possibility that disconnection will occur on the convex portion 60 or that peeling will occur in the subsequent step of the manufacturing process.

  Therefore, as in the liquid crystal display device 500D shown in FIGS. 24A and 24B, when the individual protrusions 60D are completely included in the openings 14a, the solid portions 14b are formed. Since the conductive film is formed on the flat surface of the substrate 11, there is no risk of disconnection or peeling. The convex portion 60D is not formed so as to completely surround the unit solid portion 14b ′ in a substantially circular shape, but a substantially circular liquid crystal domain corresponding to the unit solid portion 14b ′ is formed. Similar to the example, its radial tilt orientation is stabilized.

  The effect of stabilizing the radial inclined alignment by forming the convex portions 60 in the openings 14a is not limited to the openings 14a having the pattern illustrated, but for the openings 14a having all patterns described in the first embodiment. Can be applied in the same manner, and the same effect can be obtained. In addition, in order to fully exhibit the alignment stabilization effect with respect to the external force by the convex part 60, the pattern of the convex part 60 (pattern when viewed from the normal direction of the substrate) surrounds the liquid crystal layer 30 in as wide a region as possible. The shape is preferred. Therefore, for example, the positive pattern having the circular unit solid portion 14b 'has a larger alignment stabilizing effect by the convex portion 60 than the negative pattern having the circular opening 14a.

  In the liquid crystal display device according to the present invention, since an opening is provided in the pixel electrode, a sufficient voltage is not applied to the liquid crystal layer in a region corresponding to the opening, and a sufficient retardation change cannot be obtained. There may be a problem that the light utilization efficiency is lowered. Therefore, a dielectric layer is provided on the side opposite to the liquid crystal layer of the electrode provided with the opening (upper layer electrode), and an additional electrode (lower layer electrode) facing at least a part of the opening of the electrode through this dielectric layer By providing (that is, a two-layer structure electrode), a sufficient voltage can be applied to the liquid crystal layer corresponding to the opening, and light utilization efficiency and response characteristics can be improved.

  25 (a) to 25 (c), a liquid crystal display device including a picture element electrode (two-layer structure electrode) 16 having a lower layer electrode 12, an upper layer electrode 14, and a dielectric layer 13 provided therebetween. A cross-sectional structure of one picture element region 600 is schematically shown. The upper electrode 14 of the picture element electrode 16 is substantially equivalent to the picture element electrode 14 described above, and has openings and solid parts having the various shapes and arrangements described above. Hereinafter, the function of the pixel electrode 16 having a two-layer structure will be described.

  The pixel electrode 16 of the liquid crystal display device 600 has a plurality of openings 14a (including 14a1 and 14a2). FIG. 25A schematically shows the alignment state (OFF state) of the liquid crystal molecules 30a in the liquid crystal layer 30 to which no voltage is applied. FIG. 25B schematically shows a state where the alignment of the liquid crystal molecules 30a starts to change according to the voltage applied to the liquid crystal layer 30 (ON initial state). FIG. 25 (c) schematically shows a state where the alignment of the liquid crystal molecules 30a changed according to the applied voltage has reached a steady state. In FIG. 25, the lower layer electrode 12 provided so as to face the openings 14a1 and 14a2 via the dielectric layer 13 overlaps with the openings 14a1 and 14a2, respectively, and between the openings 14a1 and 14a2. However, the arrangement of the lower layer electrode 12 is not limited to this, and the lower layer electrode 12 is provided for each of the openings 14a1 and 14a2. 12 area = area of opening 14a, or area of lower layer electrode 12 <area of opening 14a. That is, the lower layer electrode 12 may be provided so as to face at least a part of the opening 14a with the dielectric layer 13 in between. However, in the configuration in which the lower layer electrode 12 is formed in the opening 14 a, there is a region (gap region) where neither the lower layer electrode 12 nor the upper layer electrode 14 exists in the plane viewed from the normal direction of the substrate 11. Since a sufficient voltage may not be applied to the liquid crystal layer 30 in the region opposite to the gap region, the width of the gap region may be sufficiently narrowed to stabilize the alignment of the liquid crystal layer 30. Preferably, it is typically preferred not to exceed about 4 μm. In addition, the lower layer electrode 12 formed at a position facing the region where the conductive layer of the upper layer electrode 14 exists through the dielectric layer 13 does not substantially affect the electric field applied to the liquid crystal layer 30, so that it is particularly patterned. However, patterning may be performed.

  As shown in FIG. 25A, when the pixel electrode 16 and the counter electrode 22 are at the same potential (a state where no voltage is applied to the liquid crystal layer 30), the liquid crystal molecules 30a in the pixel region are It is oriented perpendicular to the surfaces of both substrates 11 and 21. Here, for the sake of simplicity, it is assumed that the upper electrode 14 and the lower electrode 12 of the pixel electrode 16 have the same potential.

  When a voltage is applied to the liquid crystal layer 30, a potential gradient represented by the equipotential line EQ shown in FIG. In the liquid crystal layer 30 positioned between the upper electrode 14 and the counter electrode 22 of the pixel electrode 16, a uniform potential represented by equipotential lines EQ parallel to the surfaces of the upper electrode 14 and the counter electrode 22 A potential gradient is formed. In the liquid crystal layer 30 located above the openings 14a1 and 14a2 of the upper layer electrode 14, a potential gradient corresponding to the potential difference between the lower layer electrode 12 and the counter electrode 22 is formed. At this time, since the potential gradient formed in the liquid crystal layer 30 is affected by the voltage drop due to the dielectric layer 13, the equipotential lines EQ formed in the liquid crystal layer 30 correspond to the openings 14a1 and 14a2. It falls in the region (a plurality of “valleys” are formed in the equipotential line EQ). Since the lower layer electrode 12 is formed in a region facing the openings 14a1 and 14a2 via the dielectric layer 13, the upper layer electrode is also formed in the liquid crystal layer 30 located near the center of each of the openings 14a1 and 14a2. 14 and a potential gradient represented by an equipotential line EQ parallel to the surface of the counter electrode 22 is formed (“bottom of the valley” of the equipotential line EQ). An oblique electric field represented by an inclined equipotential line EQ is formed in the liquid crystal layer 30 on the edge portion of the opening portions 14a1 and 14a2 (the inner periphery of the opening portion including the boundary (outward extension) of the opening portion) EG. .

  As is clear from a comparison between FIG. 25B and FIG. 2A, the liquid crystal display device 600 includes the lower layer electrode 12, so that the liquid crystal molecules in the liquid crystal domain formed in the region corresponding to the opening 14 a are also included. A sufficiently large electric field can be applied.

  A torque that attempts to align the axial direction of the liquid crystal molecules 30a in parallel with the equipotential line EQ acts on the liquid crystal molecules 30a having negative dielectric anisotropy. Accordingly, the liquid crystal molecules 30a on the edge portion EG are rotated clockwise in the right edge portion EG in the drawing and counterclockwise in the left edge portion EG in the drawing, as indicated by arrows in FIG. Each direction is inclined (rotated) and oriented parallel to the equipotential line EQ.

  As shown in FIG. 25B, an electric field (an oblique electric field) represented by an equipotential line EQ inclined with respect to the axial direction of the liquid crystal molecules 30a at the edge portions EG of the openings 14a1 and 14a2 of the liquid crystal display device 600. 3), the liquid crystal molecules 30a are tilted in a direction (in the illustrated example, counterclockwise) with a small amount of tilt to be parallel to the equipotential line EQ. Further, as shown in FIG. 3C, the liquid crystal molecules 30a located in the region where the electric field expressed by the equipotential line EQ perpendicular to the axis direction of the liquid crystal molecules 30a is inclined are equipotential. The liquid crystal molecules 30a positioned on the line EQ are tilted in the same direction as the liquid crystal molecules 30a positioned on the tilted equipotential line EQ so that the alignment is continuous (matched) with the liquid crystal molecules 30a.

  As described above, when the change of orientation starting from the liquid crystal molecules 30a located on the inclined equipotential line EQ progresses and reaches a steady state, as schematically shown in FIG. 25 (c), the openings 14a1 and A symmetrical tilt orientation (radial tilt orientation) is formed with respect to each center SA of 14a2. Further, the liquid crystal molecules 30a on the region of the upper electrode 14 located between the two adjacent openings 14a1 and 14a2 are also aligned with the liquid crystal molecules 30a at the edges of the openings 14a1 and 14a2 ( Tilted to align). Since the liquid crystal molecules 30a on the portions located at the centers of the edges of the openings 14a1 and 14a2 are affected to the same extent by the liquid crystal molecules 30a at the respective edges, the liquid crystal molecules located at the center of the openings 14a1 and 14a2 As in 30a, the vertical alignment state is maintained. As a result, the liquid crystal layer on the upper electrode 14 between the two adjacent openings 14a1 and 14a2 is also in a radially inclined alignment state. However, the tilt direction of the liquid crystal molecules is different between the radial tilt alignment of the liquid crystal layer in the openings 14a1 and 14a2 and the radial tilt direction of the liquid crystal layer between the openings 14a1 and 14a2. When attention is paid to the alignment in the vicinity of the liquid crystal molecules 30a located at the center of each radially inclined alignment region shown in FIG. 25 (c), cones extending toward the counter electrode are formed in the openings 14a1 and b14a2. While the liquid crystal molecules 30a are inclined so as to form, the liquid crystal molecules 30 are inclined so as to form a cone extending toward the upper electrode 14 between the openings. In addition, since any radial inclination alignment is formed so that it may correspond with the inclination alignment of the liquid crystal molecule 30a of an edge part, two radial inclination alignment is mutually continuous.

  As described above, when a voltage is applied to the liquid crystal layer 30, the liquid crystal molecules 30 a in the peripheral region start to tilt from the liquid crystal molecules 30 a on the edge portions EG of the openings 14 a 1 and 14 a 2 provided in the upper electrode 14. By tilting so as to match the tilt alignment of the liquid crystal molecules 30a on the edge portion EG, a radial tilt alignment is formed. Therefore, as the number of openings 14a formed in one picture element region increases, the number of liquid crystal molecules 30a that start to tilt first in response to an electric field increases. Therefore, the radial tilt alignment over the entire picture element region. The time required to form is shortened. That is, the response speed of the liquid crystal display device can be improved by increasing the number of openings 14a formed in the pixel electrode 16 for each pixel region. Moreover, since the pixel electrode 16 is a two-layer structure electrode having the upper layer electrode 14 and the lower layer electrode 12, a sufficient electric field can be applied to the liquid crystal molecules in the region corresponding to the opening 14a. The response characteristic of the display device is improved.

  When the two-layer structure electrode 16 as described above is employed, for example, as shown in FIG. 26, the auxiliary capacitance electrode 8 functions as a part of the lower layer electrode 12 and the second insulating layer 7 serves as the dielectric layer 13. Can function.

  The liquid crystal display device having the pixel electrode 16 having the two-layer structure can constitute not only a transmission type and a reflection type but also a transmission / reflection type liquid crystal display device (see, for example, JP-A-11-101992). .

  The transflective liquid crystal display device (hereinafter abbreviated as “bipolar liquid crystal display device”) includes, in a pixel area, a transmissive region T for displaying in the transmissive mode and a reflective region R for displaying in the reflective mode. It refers to a liquid crystal display device (see FIG. 25A). The transmissive region T and the reflective region R are typically defined by a transparent electrode and a reflective electrode. Instead of the reflective electrode, the reflective region can be defined by a structure in which the reflective layer and the transparent electrode are combined.

  This dual-use liquid crystal display device can display by switching between the reflection mode and the transmission mode, or can simultaneously display in both display modes. Therefore, for example, it is possible to realize a reflection mode display in an environment where the ambient light is bright, and a transmission mode display in a dark environment. In addition, when both modes are displayed at the same time, the transmissive mode LCD device is used in an environment where the ambient light is bright (fluorescent light or sunlight is directly incident on the display surface at a specific angle). In the contrast ratio can be suppressed. In this way, the drawbacks of the transmissive liquid crystal display device can be compensated. The area ratio between the transmissive region T and the reflective region R can be set as appropriate according to the application of the liquid crystal display device. Further, in a liquid crystal display device used exclusively as a transmission type, the above-described drawbacks of the transmission type liquid crystal display device can be compensated even if the area ratio of the reflection region is reduced to such an extent that display in the reflection mode is not possible.

  As shown in FIG. 25A, for example, by using the upper electrode 14 of the liquid crystal display device 600 as a reflective electrode and the lower electrode 12 as a transparent electrode, a dual-use liquid crystal display device can be obtained. However, the thickness of the liquid crystal layer 30 in the reflective region R and the thickness of the liquid crystal layer 30 in the transmissive region T are adjusted to match the voltage-transmittance characteristics of the display in the reflective mode and the transmissive mode. It is preferable to adjust the voltage applied to the lower electrode 12 and the voltage applied to the lower layer electrode 12.

(Disposition of polarizing plate and retardation plate)
A so-called vertical alignment type liquid crystal display device including a liquid crystal layer in which liquid crystal molecules having negative dielectric anisotropy are vertically aligned when no voltage is applied can perform display in various display modes. For example, in addition to the birefringence mode for displaying by controlling the birefringence of the liquid crystal layer by an electric field, the optical rotation mode or a combination of the optical rotation mode and the birefringence mode is applied to the display mode. A birefringence mode liquid crystal display device is obtained by providing a pair of polarizing plates outside (on the side opposite to the liquid crystal layer 30) a pair of substrates (for example, a TFT substrate and a counter substrate) of all the liquid crystal display devices described above. Can do. Moreover, you may provide a phase difference compensation element (typically phase difference plate) as needed. Furthermore, a bright liquid crystal display device can be obtained even if substantially circularly polarized light is used.

(Other embodiments)
Up to this point, the present invention has been described with respect to a liquid crystal display device having an alignment regulating structure (an electrode structure having a unit solid part and an opening) for forming a liquid crystal domain having a radially inclined alignment state. However, the present invention is not limited to this, and can be widely used in all liquid crystal display devices that include a vertical alignment type liquid crystal layer that takes a vertical alignment state when no voltage is applied, and whose alignment is regulated by an electrode structure having openings and slits. The effective aperture ratio of such a liquid crystal display device can be improved.

  With reference to FIGS. 27A and 27B, another liquid crystal display device 700 according to the present invention will be described. The liquid crystal display device 700 is a so-called MVA (Multi-domain Vertically Aligned) type liquid crystal display device. FIG. 27A is a top view seen from the normal direction of the substrate, and FIG. 27B corresponds to a cross-sectional view taken along line 27B-27B ′ in FIG. FIG. 27B shows a state where a voltage is applied to the liquid crystal layer.

  The liquid crystal display device 700 includes an active matrix substrate (TFT substrate) 700a, a counter substrate (color filter substrate) 700b, and a vertical alignment type liquid crystal layer 30 provided between the TFT substrate 700a and the counter substrate 700b. is doing.

  The liquid crystal molecules 30a included in the liquid crystal layer 30 have a negative dielectric anisotropy, and a vertical alignment film (non-alignment film) as a vertical alignment layer provided on the surface of the TFT substrate 700a and the counter substrate 700b on the liquid crystal layer 30 side. When a voltage is not applied to the liquid crystal layer 30, the liquid crystal layer 30 is aligned perpendicularly to the surface of the vertical alignment film.

  A TFT substrate 700a of the liquid crystal display device 700 has a transparent substrate (for example, a glass substrate) 11 and a pixel electrode 19 formed on the surface thereof. The counter substrate 700b has a transparent substrate (for example, a glass substrate) 21 and a counter electrode 22 formed on the surface thereof. The alignment state of the liquid crystal layer 30 for each pixel region changes according to the voltage applied to the pixel electrode 19 and the counter electrode 22 arranged so as to face each other via the liquid crystal layer 30. Display is performed using a phenomenon in which the polarization state and amount of light transmitted through the liquid crystal layer 30 change in accordance with the change in the alignment state of the liquid crystal layer 30.

  The pixel electrode 19 included in the TFT substrate 700a has a plurality of slits 19a as shown in FIG. In the upper half of the picture element, the plurality of slits 19a extend from the upper left to the lower right and are arranged in parallel to each other at a predetermined interval. In the lower half of the picture element, the plurality of slits 19a extend from the lower left to the upper right and are arranged in parallel to each other at a predetermined interval.

  When a voltage is applied between the pixel electrode 19 and the counter electrode 22, the liquid crystal layer 30 on the edge of the slit 19a of the pixel electrode 19 (the inner periphery of the slit 19a including the boundary (extended) of the slit 19a) is formed. Forms an oblique electric field represented by an inclined equipotential line EQ. Accordingly, the liquid crystal molecules 30a having negative dielectric anisotropy in the vertical alignment state when no voltage is applied are inclined along the inclination direction of the oblique electric field generated at the edge portion of the slit 19a when the voltage is applied. That is, the orientation of the liquid crystal layer 30 is regulated by an oblique electric field generated at the edges of the plurality of slits 19 a of the pixel electrode 19 when a voltage is applied between the pixel electrode 19 and the counter electrode 22. .

  In the liquid crystal display device 700, the alignment of the liquid crystal layer 30 is regulated by an oblique electric field generated at the edge of the slit 19a. As a result, when a voltage is applied, the liquid crystal molecules 30a in the pixel region are orthogonal to the edge of the slit 19a. Oriented in four directions (upper right direction, lower right direction, upper left direction, lower left direction in FIG. 27A). In other words, in the liquid crystal display device 700, the picture element region is divided in orientation. Therefore, the liquid crystal display device 700 has a favorable viewing angle characteristic.

  The counter substrate 700b of the liquid crystal display device 700 has a plurality of ribs 29 on the surface on the liquid crystal layer 30 side. The direction in which the rib 29 extends coincides with the direction in which the slit 19a extends, and the rib 29 is provided so as to be positioned between two adjacent slits 19a.

  The surface of the rib 29 has a vertical alignment (typically, a vertical alignment film (not shown) is formed so as to cover the rib 29), and the liquid crystal molecules 30a are inclined by the rib 29. Due to the anchoring effect of the side surface 29s, it is oriented substantially perpendicular to the inclined side surface 29s. When a voltage is applied to the liquid crystal layer 30 in such a state, the other liquid crystal molecules 30a in the vicinity of the rib 29 are tilted so as to be aligned with the tilted alignment on the tilted side surface 29s due to the anchoring effect of the tilted side surface 29s of the rib 29s. .

  Since the alignment regulating direction by the oblique electric field generated at the edge portion of the slit 19a of the pixel electrode 19 and the alignment regulating direction by the rib 29 match, the alignment of the liquid crystal layer that is divided by the oblique electric field when a voltage is applied is It is further stabilized by the ribs 29. In the present embodiment, the counter substrate 700b has a configuration having a plurality of ribs 29 provided in a corresponding region between the plurality of slits 19a of the picture element electrode 19. The electrode 22 may have a plurality of slits provided in a corresponding region between the plurality of slits 19 a of the pixel electrode 19.

  An auxiliary capacitor 44 is formed on the TFT substrate 700 a of the liquid crystal display device 700. Specifically, the auxiliary capacitor 44 includes an auxiliary capacitor line 6, an auxiliary capacitor electrode 8 facing the auxiliary capacitor line 6 and electrically connected to a drain electrode of a thin film transistor (not shown), and between them. The first insulating layer (first interlayer insulating film) 3 is provided.

  The auxiliary capacitance wiring 6 has a wiring trunk 6a extending substantially parallel to the scanning wiring (not shown here), and four wiring branches 6b extending from the wiring trunk 6a and extending along the slit 19a. The auxiliary capacitance electrode 8 extends from the electrode trunk 8a and the electrode trunk 8a facing the wiring trunk 6a via the first insulating layer 3, and extends to the wiring branch 6b via the first insulating layer 3. And an opposing electrode branch 8b.

  A second insulating layer (second interlayer insulating film) 7 is provided so as to cover the wiring and the thin film transistor described above, and the pixel electrode 19 is formed on the second insulating layer 7. In the present embodiment, the second insulating layer 7 is a thick film made of a resin material.

  In the liquid crystal display device 700, as shown in FIGS. 27A and 27B, a part of the auxiliary capacitor 44 overlaps the slit 19 a of the pixel electrode 19. Specifically, a part of the wiring trunk part 6a and the electrode trunk part 8a and the wiring branch part 6b and the electrode branch part 8b are arranged so as to overlap the slit 19a, whereby a part of the auxiliary capacitor 44 overlaps the slit 19a. ing.

  Therefore, a reduction in effective aperture ratio (transmittance) caused by the auxiliary capacitor 44 typically including a light-shielding member is suppressed, and a region contributing to display (the conductive film in the pixel electrode 19). The area of the portion where) exists can be increased. Therefore, bright display is realized.

  In the present embodiment, the TFT substrate 700 a has the second insulating layer 7 that covers the thin film transistor and the auxiliary capacitance electrode 8, and the pixel electrode 19 is formed on the second insulating layer 7. Therefore, the pixel electrode 19 can be provided so as to partially overlap the thin film transistor, the scanning wiring, the signal wiring, and the like, and the aperture ratio can be further improved.

  In order to generate an oblique electric field with sufficient strength for regulating the orientation at the edge portion of the slit 19a, the second insulating layer 7 is preferably a thick film as in this embodiment. The auxiliary capacitance electrode 8 constituting the auxiliary capacitance 44 is electrically connected to the drain electrode of the thin film transistor and has substantially the same potential as the conductive film of the pixel electrode 19. For this reason, if a part of the auxiliary capacitance electrode 8 overlaps the slit 19a, the equipotential line EQ generated at the time of voltage application is not sufficiently dropped by the slit 19a, and an oblique electric field having a sufficient strength at the edge of the slit 19a. May not be generated.

  If the second insulating layer 7 is made thick, the voltage drop due to the second insulating layer 7 can be made sufficiently large, and the equipotential line EQ can be sufficiently lowered by the slit 19a. An oblique electric field with a sufficient strength can be generated. Further, since the surface of the second insulating layer 7 on the liquid crystal layer 30 side can be substantially flattened by making the second insulating layer 7 thick, the pixel electrode formed thereon It is possible to prevent the step 19 from being generated.

  In order to obtain a sufficiently strong alignment regulating force, the thickness of the second insulating layer 7 is specifically preferably 1 μm or more, and more preferably 2.5 μm or more. Further, when the second insulating layer 7 is formed from a resin material (for example, a transparent resin material having photosensitivity such as acrylic resin), it is easy to increase the thickness of the second insulating layer 7.

  From the viewpoint of sufficiently improving the aperture ratio, it is preferable that as much of the auxiliary capacitor 44 as possible overlaps with the slit 19 a of the pixel electrode 19. Specifically, it is preferable that ¼ or more of the auxiliary capacitor 44 overlaps the slit 19a, more preferably ½ or more overlap, and it is more preferable that almost all the portions overlap. In the present embodiment, the auxiliary capacitance wiring 6 and the auxiliary capacitance electrode 8 have a wiring branch portion 6b and an electrode branch portion 8b extending along the slit 19a. As described above, when the auxiliary capacitance wiring 6 and the auxiliary capacitance electrode 8 have a branch structure, a larger portion of the auxiliary capacitance 44 can be overlapped with the slit 19a (or the opening), and the design has a high aperture ratio. Can be easily realized.

FIG. 2 is a diagram schematically showing the structure of one picture element region of the liquid crystal display device 100 according to the present invention, where (a) is a top view and (b) is a cross-sectional view taken along line 1B-1B ′ in FIG. It is. It is a figure which shows the state which applied the voltage to the liquid crystal layer 30 of the liquid crystal display device 100, (a) shows the state (ON initial state) which the orientation began to change typically, (b) is a steady state Is schematically shown. (A)-(d) is a figure which shows typically the relationship between an electric-force line and the orientation of a liquid crystal molecule. (A)-(c) is a figure which shows typically the orientation state of the liquid crystal molecule seen from the substrate normal line direction in the liquid crystal display device 100 by this invention. (A)-(c) is a figure which shows typically the example of the radial inclination alignment of a liquid crystal molecule. (A) And (b) is a top view which shows typically the other pixel electrode used for the liquid crystal display device by this invention. (A) And (b) is a top view which shows typically the other pixel electrode used for the liquid crystal display device by this invention. (A) And (b) is a top view which shows typically the other pixel electrode used for the liquid crystal display device by this invention. It is a top view which shows typically the further other pixel electrode used for the liquid crystal display device by this invention. (A) And (b) is a top view which shows typically the other pixel electrode used for the liquid crystal display device by this invention. (A) is a figure which shows typically the unit cell of the pattern shown to Fig.1 (a), (b) is a figure which shows the unit cell of the pattern shown in FIG. c) is a graph showing the relationship between the pitch p and the solid area ratio. FIG. 2 is a diagram schematically showing the structure of one picture element region of the liquid crystal display device 100 according to the present invention, in which (a) is a top view and (b) is a cross-sectional view taken along line 12B-12B ′ in FIG. It is. It is a figure which shows the equivalent circuit of the liquid crystal display device 100 by this invention. (A) And (b) is sectional drawing which shows typically the liquid crystal display device provided with the thin film as a 2nd insulating layer. It is a figure which shows typically the structure of one picture element area | region of the other liquid crystal display device 200 by this invention, (a) is a top view, (b) followed 15B-15B 'line in (a). It is sectional drawing. It is a figure which shows typically the structure of one picture element area | region of the other liquid crystal display device 300 by this invention. (A)-(d) is a figure which shows typically the opposing board | substrate 400b which has the orientation control structure 28. FIG. FIG. 6 is a diagram schematically showing a cross-sectional structure of one picture element region of the liquid crystal display device 400 having an alignment regulation structure, where (a) shows a state in which no voltage is applied, and (b) shows a state in which the orientation starts to change (ON (C) shows a steady state. It is a figure which shows typically the structure of one picture element area | region of the other liquid crystal display device 500 by this invention, (a) is a top view, (b) is along the 19B-19B 'line in (a). It is sectional drawing. (A)-(d) is a schematic diagram for demonstrating the relationship between the orientation of the liquid crystal molecule 30a, and the shape of the surface which has vertical orientation. It is a figure which shows the state which applied the voltage to the liquid crystal layer 30 of the liquid crystal display device 500, (a) shows the state (ON initial state) where the orientation started changing, (b) is a steady state Is schematically shown. (A)-(c) is typical sectional drawing of liquid crystal display device 500A, 500B and 500C from which the arrangement | positioning relationship of an opening part and a convex part differs. It is a figure which shows typically the cross-section of the liquid crystal display device 500, and is sectional drawing which followed the 23A-23A 'line | wire in Fig.19 (a). It is a figure which shows typically the structure of one picture element area | region of other liquid crystal display device 500D by this invention, (a) is a top view, (b) is along the 24B-24B 'line in (a). It is sectional drawing. It is a figure which shows typically the cross-sectional structure of one picture element area | region of the liquid crystal display device 600 provided with a two-layer structure electrode, (a) shows a no-voltage application state, (b) is the state which the orientation began to change ( (ON initial state), and (c) shows a steady state. It is a figure which shows typically the cross-section of one pixel area | region of the liquid crystal display device 600 provided with a two-layer structure electrode. It is a figure which shows typically the structure of one picture element area | region of the other liquid crystal display device 700 by this invention, (a) is a top view, (b) is along the 27B-27B 'line in (a). It is sectional drawing.

Explanation of symbols

2 Scanning wiring 3 First insulating layer (first interlayer insulating film)
4 signal wiring 6 auxiliary capacity wiring 6a wiring trunk 6b wiring branch 7 second insulating layer (second interlayer insulating film)
8 Auxiliary Capacitance Electrode 8a Electrode Trunk 8b Electrode Branch 11, 21 Transparent Insulating Substrate 12 Lower Electrode 13 Dielectric Layer 14 Pixel Electrode 14a Opening 14b Solid Part (Conductive Film)
14b 'unit solid part 16 picture element electrode (two-layer structure electrode)
19 picture element electrode 19a slit 22 counter electrode 22b convex part 28 alignment regulating structure 29 rib 30 liquid crystal layer 30a liquid crystal molecule 40 picture element capacity 42 liquid crystal capacity 44 auxiliary capacity (storage capacity)
50 Thin film transistor (switching element)
60 Projection 100, 200, 300, 400 Liquid crystal display device 100a, 200a TFT substrate (active matrix substrate)
100b, 200b, 400b Counter substrate (color filter substrate)
500, 600, 700 Liquid crystal display device 500a, 700a TFT substrate (active matrix substrate)
700b Counter substrate (color filter substrate)

Claims (33)

A first substrate, a second substrate, a liquid crystal layer provided between the first substrate and the second substrate, and having a plurality of pixel regions;
The first substrate includes a pixel electrode provided for each of the plurality of pixel regions on the liquid crystal layer side, and a switching element electrically connected to the pixel electrode,
The second substrate has a counter electrode facing the pixel electrode through the liquid crystal layer,
In each of the plurality of pixel regions, the pixel electrode has a solid portion including a plurality of unit solid portions, and the liquid crystal layer has a voltage between the pixel electrode and the counter electrode. Periphery of each of the plurality of unit solid portions of the pixel electrode when a vertical alignment state is applied when no voltage is applied and a voltage is applied between the pixel electrode and the counter electrode A liquid crystal display device that forms a liquid crystal domain in a radially inclined alignment state in a region corresponding to each of the plurality of unit solid portions by an oblique electric field generated in
In each of the plurality of pixel regions, further comprising an auxiliary capacitor electrically connected in parallel to a liquid crystal capacitor constituted by the pixel electrode and the counter electrode and the liquid crystal layer,
The first substrate has a region where the solid portion of the pixel electrode is not provided in each of the plurality of pixel regions.
The liquid crystal display device, wherein at least a part of the auxiliary capacitor is located in a region where the solid portion of the first substrate is not provided.   The liquid crystal display device according to claim 1, wherein the switching element is a thin film transistor.   The auxiliary capacitance is provided between an auxiliary capacitance wiring, an auxiliary capacitance electrode facing the auxiliary capacitance wiring and electrically connected to a drain electrode of the thin film transistor, and between the auxiliary capacitance wiring and the auxiliary capacitance electrode. The liquid crystal display device according to claim 2, further comprising: a first insulating layer.   4. The liquid crystal display device according to claim 3, wherein at least a part of the storage capacitor line, at least a part of the storage capacitor electrode, and at least a part of the first insulating layer are located in the region.   5. The liquid crystal display according to claim 3, wherein the first substrate includes a scanning wiring electrically connected to a gate electrode of the thin film transistor and a signal wiring electrically connected to a source electrode of the thin film transistor. apparatus. The auxiliary capacitance wiring has at least one wiring trunk extending substantially parallel to the scanning wiring, and a wiring branch extending from the wiring trunk,
6. The liquid crystal according to claim 5, wherein the auxiliary capacitance electrode has at least one electrode trunk that faces the wiring trunk via the first insulating layer, and an electrode branch extending from the electrode trunk. Display device.   The liquid crystal display device according to claim 6, wherein the wiring branch part and the electrode branch part are extended so as to overlap one central portion of the plurality of unit solid parts.   The liquid crystal display device according to claim 6, wherein the at least one wiring trunk is a plurality of wiring trunks, and the at least one electrode trunk is a plurality of electrode trunks. The first substrate further includes a second insulating layer covering at least the thin film transistor and the auxiliary capacitance electrode,
The liquid crystal display device according to claim 3, wherein the pixel electrode is formed on the second insulating layer.   The liquid crystal display device according to claim 9, wherein the second insulating layer is formed of a resin material.   11. The liquid crystal display device according to claim 1, wherein each of the plurality of unit solid portions has rotational symmetry.   The liquid crystal display device according to claim 1, wherein each of the plurality of unit solid portions has a substantially circular shape.   12. The liquid crystal display device according to claim 1, wherein each of the plurality of unit solid portions has a substantially rectangular shape with a corner portion having a substantially arc shape.   12. The liquid crystal display device according to claim 1, wherein each of the plurality of unit solid portions has a shape in which a corner portion is sharpened.   The plurality of unit solid portions form at least one unit cell having substantially the same shape and the same size, and arranged to have rotational symmetry. A liquid crystal display device according to 1.   The pixel electrode further includes at least one opening, and the liquid crystal layer has the at least one opening formed by the oblique electric field when a voltage is applied between the pixel electrode and the counter electrode. The liquid crystal display device according to claim 1, wherein a liquid crystal domain having a radially inclined alignment state is formed in a region corresponding to the opening.   The at least one opening includes a plurality of openings having substantially the same shape and the same size, and at least some of the openings are arranged to have rotational symmetry. The liquid crystal display device according to claim 16, wherein at least one unit cell is formed.   The liquid crystal display device according to claim 17, wherein each shape of the at least some of the plurality of openings has rotational symmetry.   The liquid crystal display device according to claim 17 or 18, wherein each of the at least some of the plurality of openings has a substantially circular shape.   The sum of the areas of the plurality of openings of the pixel electrode in each of the plurality of pixel regions is smaller than the area of the solid part of the pixel electrode. Liquid crystal display device.   A convex portion is further provided inside each of the plurality of openings of the pixel electrode, and a cross-sectional shape of the convex portion in the in-plane direction of the substrate is the same as the shape of the plurality of openings, and the convex 21. The liquid crystal display device according to claim 17, wherein the side surface of the portion has an alignment regulating force in the same direction as the alignment regulating direction by the oblique electric field with respect to the liquid crystal molecules of the liquid crystal layer.   The second substrate has a radial inclination in a state where a voltage is applied between at least the pixel electrode and the counter electrode in a region corresponding to each of the plurality of unit solid portions. The liquid crystal display device according to claim 1, wherein the liquid crystal display device has an alignment control structure that expresses an alignment control force for alignment.   23. The liquid crystal display device according to claim 22, wherein the alignment restricting structure is provided in a region corresponding to the vicinity of the center of each of the plurality of unit solid portions.   24. In the liquid crystal domain formed corresponding to each of the plurality of unit solid portions, an alignment control direction by the alignment control structure is aligned with a direction of a radially inclined alignment by the oblique electric field. A liquid crystal display device according to 1.   The liquid crystal display device according to any one of claims 22 to 24, wherein the alignment regulating structure exhibits an alignment regulating force even in a state where a voltage is not applied between the pixel electrode and the counter electrode.   The liquid crystal display device according to any one of claims 22 to 25, wherein the alignment regulating structure is a convex portion protruding toward the liquid crystal layer of the counter substrate.   27. The liquid crystal display device according to claim 25, wherein a part of the auxiliary capacitor overlaps the alignment regulating structure.   The liquid crystal display device according to any one of claims 1 to 27, wherein the liquid crystal domain takes a spiral radial tilt alignment state. A first substrate, a second substrate, a liquid crystal layer provided between the first substrate and the second substrate, and having a plurality of pixel regions;
The first substrate includes a pixel electrode provided for each of the plurality of pixel regions on the liquid crystal layer side, and a switching element electrically connected to the pixel electrode,
The second substrate has a counter electrode facing the pixel electrode through the liquid crystal layer,
In each of the plurality of pixel regions, the pixel electrode has at least one opening or slit, and no voltage is applied between the pixel electrode and the counter electrode in the liquid crystal layer. Occasionally in a vertically aligned state and when a voltage is applied between the pixel electrode and the counter electrode, it is generated at the at least one opening of the pixel electrode or the edge of the slit. A liquid crystal display device whose orientation is regulated by an oblique electric field,
In each of the plurality of pixel regions, further comprising an auxiliary capacitor electrically connected in parallel to a liquid crystal capacitor constituted by the pixel electrode and the counter electrode and the liquid crystal layer,
A liquid crystal display device, wherein at least a part of the auxiliary capacitance overlaps the at least one opening or slit of the pixel electrode.   30. The liquid crystal display device according to claim 29, wherein the switching element is a thin film transistor.   The auxiliary capacitance is provided between an auxiliary capacitance wiring, an auxiliary capacitance electrode facing the auxiliary capacitance wiring and electrically connected to a drain electrode of the thin film transistor, and between the auxiliary capacitance wiring and the auxiliary capacitance electrode. The liquid crystal display device according to claim 30, further comprising: a first insulating layer. The first substrate further includes a second insulating layer covering at least the thin film transistor and the auxiliary capacitance electrode,
32. The liquid crystal display device according to claim 31, wherein the pixel electrode is formed on the second insulating layer.   The liquid crystal display device according to claim 32, wherein the second insulating layer is formed of a resin material.

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