JP2013117700A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lateral electric field mode liquid crystal display device with high display quality.SOLUTION: A liquid crystal display device comprises: a first substrate and a second substrate having a liquid crystal layer interposed therebetween; a first polarizer; a first electrode and a second electrode provided for the first substrate; and a first alignment film regulating the alignment direction of a liquid crystal molecule when no voltage is applied. The first alignment film includes a first alignment region where the liquid crystal molecule is aligned in a first direction and a second alignment region where the liquid crystal molecule is aligned in a second direction. The first direction and the second direction are different from the polarization axis direction of the first polarizer. When voltage is applied between the first electrode and the second electrode, the liquid crystal molecule in a first domain and the liquid crystal molecule in a second domain rotate in directions opposite to each other and the longitudinal direction of the liquid crystal molecule in the first domain and the longitudinal direction of the liquid crystal molecule in the second domain become parallel to the polarization axis direction of the first polarizer during the rotation.

Description

  The present invention relates to a liquid crystal display device, and more particularly to a horizontal electric field mode liquid crystal display device.

  The performance of liquid crystal display devices is increasing with the expansion of applications. In particular, display modes such as MVA (Multi-domain Vertical Alignment) and IPS (In Plane Switching) having wide viewing angle characteristics have been developed, and further improvements are being made.

  In recent years, a liquid crystal display device in an FFS (Fringe Field Switching) mode, which is an extension of the IPS mode, has also been developed. In these display modes, an electric field is generated in the in-plane direction (or oblique direction) using an electrode provided on one of the substrates sandwiching the liquid crystal layer, and the liquid crystal molecules are rotated in the substrate plane by this electric field. The display is performed. The IPS mode and the FFS mode are display modes that are also called horizontal electric field modes (lateral electric field methods).

  Japanese Patent Application Laid-Open No. H10-260260 describes a technique of arranging a polarization axis direction of a polarizing plate arranged outside a liquid crystal layer so as to be shifted from an initial alignment direction of liquid crystal molecules in a horizontal electric field mode liquid crystal display device. . In such a configuration, the transmittance of the liquid crystal layer can be minimized when a voltage exceeding 0 V is applied.

  Thereby, for example, even when the voltage supply of 0V is not stable, a black display can be stably performed by applying a voltage exceeding 0V. Therefore, the contrast ratio can be kept high, and the display quality can be improved.

JP 2007-93665 A International Publication No. 2009/157207

Japanese Journal of Applied Physics Vol.41 (2002) pp. 2944-2948

  In the liquid crystal display device described in Patent Document 1, a plurality of elongated electrode portions constituting the pixel electrode are formed to extend only in one direction. Further, the initial alignment direction (when no voltage is applied) of the liquid crystal molecules is the same in any region in the pixel. The alignment film used to define the alignment direction of the liquid crystal layer is rubbed in one direction, and the liquid crystal is displaced in the direction deviated from the polarization axis by the alignment regulating force obtained by the rubbing process. The molecules are oriented.

  Such a configuration is not so difficult to realize in a so-called single domain liquid crystal display device in which pixels are configured by a single liquid crystal domain. This is because it is relatively easy to dispose the polarizing plate so that the polarization axis direction is shifted with respect to the initial alignment direction determined by the rubbing direction. In a single domain liquid crystal display device, since liquid crystal molecules rotate in the same direction, a state in which the transmittance is minimized when a low voltage is applied can be realized in each pixel. However, since the liquid crystal display device of Patent Document 1 has a single domain configuration, there is a problem that color displacement is likely to occur particularly when viewed from an oblique direction.

  On the other hand, in order to suppress color displacement when viewed from an oblique direction, there is known a liquid crystal display device that forms a dual domain by changing the extending direction of the pixel electrode depending on the domain (for example, Non-Patent Document 1). ). The dual-domain liquid crystal display device is configured so that the rotation direction and alignment state of liquid crystal molecules when a voltage is applied are different in each domain. This suppresses deterioration of display quality depending on the viewing angle.

  However, in the conventional dual domain liquid crystal display device, the initial alignment direction defined by the rubbing direction and the polarization axis direction of the polarizing plate are configured to coincide with each other. For this reason, in order to perform an appropriate black display, it is necessary to drive to always supply 0V. However, it may not be easy to stably supply 0 V depending on the driving method. In this case, since black display cannot be stably performed, it is not easy to realize a high contrast ratio.

  Further, when the signal voltage and the common voltage are controlled to be the same voltage in order to supply 0 V when operating in the gate line inversion driving method for a mobile device or the like, the signal amplitude cannot be reduced. For this reason, there is a problem that it is difficult to keep power consumption low.

  Note that a dual-domain liquid crystal display device is usually designed so that the rotation directions of liquid crystal molecules are different in the two domains. For this reason, when trying to shift the polarization axis direction with respect to the initial alignment direction of the liquid crystal molecules using the method described in Patent Document 1, depending on the domain, even if a voltage exceeding 0 V is applied, black display is performed. May become unstable. In Patent Document 1, the alignment direction is set to one direction by rubbing. In this case, when the liquid crystal molecules are aligned so that one domain has an offset angle opposite to the liquid crystal rotation direction, the other domain is aligned. This is because the alignment cannot be performed so as to have an offset angle in the direction opposite to the liquid crystal rotation direction.

  The present invention has been made to solve the above-described problems, and an object thereof is to improve display quality in a horizontal electric field mode liquid crystal display device having a plurality of liquid crystal domains.

  A liquid crystal display device according to an embodiment of the present invention includes a liquid crystal layer, first and second substrates disposed to face each other with the liquid crystal layer interposed therebetween, and first and second substrates disposed on the first and second substrates, respectively. A polarizing element; a first electrode and a second electrode disposed on the liquid crystal layer side of the first substrate; and a first alignment film disposed on at least one liquid crystal layer side of the first substrate and the second substrate. And a first electric field mode liquid crystal display device that regulates an alignment direction of liquid crystal molecules when no voltage is applied, wherein the first alignment film aligns the liquid crystal molecules in the first alignment direction. And a second alignment region that is adjacent to the first alignment region and aligns the liquid crystal molecules in a second alignment direction different from the first alignment direction, the first alignment direction and the Any of the second orientation directions is the first bias. A direction different from the polarization axis direction of the element, and when a voltage is applied between the first electrode and the second electrode, the liquid crystal molecules in the first domain corresponding to the first alignment region and the second The liquid crystal molecules in the second domain corresponding to the alignment region rotate in directions opposite to each other, and both the major axis direction of the liquid crystal molecules in the first domain and the major axis direction of the liquid crystal molecules in the second domain are During the rotation, it becomes parallel to the polarization axis direction of the first polarizing element.

  In one embodiment, the first electrode includes a plurality of first electrode portions having an elongated shape, and the extending directions of the first electrode portions are different between the first domain and the second domain, When a voltage is applied between the first electrode and the second electrode, the directions of the electric fields generated in the first domain and the second domain are different from each other.

  In one embodiment, the first domain and the second domain are included in one pixel, and the first electrode is refracted at a boundary between the first domain and the second domain. It has a "" -shaped electrode part.

  In one embodiment, the extending direction of the first electrode portion has a first offset angle with respect to the polarization axis direction, and the first and second alignment directions are the polarization axis direction. On the other hand, it has a second offset angle, and the magnitude of the second offset angle is smaller than the magnitude of the first offset angle.

  In one embodiment, the first alignment film is a photo-alignment film, and the first and second alignment directions are determined by a polarization direction of polarized light applied to the photo-alignment film.

  In one embodiment, the liquid crystal display device further includes a backlight unit provided on the opposite side of the first polarizing element from the liquid crystal layer, and the polarization axis of the first polarizing element is an absorption axis. .

  In one embodiment, the liquid crystal layer is made of a liquid crystal material having positive dielectric anisotropy.

  In one embodiment, the liquid crystal display device further includes a second alignment film disposed so as to face the first alignment film with the liquid crystal layer interposed therebetween, and the second alignment film includes the first alignment film. A third alignment region for aligning liquid crystal molecules in a direction parallel to the first alignment direction of the alignment film, and a fourth alignment region for aligning liquid crystal molecules in a direction parallel to the second alignment direction, The first alignment region and the second alignment region of the first alignment film and the third alignment region and the fourth alignment region of the second alignment film are respectively arranged so as to face each other.

  In one embodiment, the liquid crystal display device further includes a second alignment film disposed so as to face the first alignment film with the liquid crystal layer interposed therebetween, and the second alignment film includes the polarizing element. The liquid crystal molecules are aligned in a third alignment direction parallel to the polarization axis direction.

  In one embodiment, the first and second alignment directions form an angle of greater than 0 ° to 2 ° with respect to the polarization axis direction.

  In one embodiment, the liquid crystal display device operates in a gate line inversion driving method, and a voltage exceeding 0 V is applied to the liquid crystal layer during black display.

  In one embodiment, the first domain and the second domain are formed corresponding to two adjacent pixels, respectively.

  According to the embodiment of the present invention, in a horizontal electric field mode liquid crystal display device, display quality can be improved while saving power consumption.

It is a top view which shows 1 pixel area | region of the liquid crystal display device concerning embodiment of this invention. It is sectional drawing along the A-A 'line of FIG. (A)-(c) is a top view for demonstrating operation | movement of the liquid crystal display device of embodiment of this invention. (A)-(c) is a top view for demonstrating operation | movement of the liquid crystal display device of a comparative example. It is a figure which shows the relationship between the initial orientation direction of a liquid crystal molecule, a polarization axis direction, and a pixel electrode direction. (A) is a circuit diagram of the liquid crystal display device of embodiment of this invention, (b) And (c) is a figure which shows the drive signal at the time of black display and white display, respectively. It is a figure for demonstrating the preparation process of the photo-alignment film of embodiment. (A) is a figure which shows the polarization direction of a photo-alignment film, (b) is a figure which shows the relationship etc. between a polarization direction and an absorption axis. (A) is a figure which shows a mode that the orientation direction is offset in the photo-alignment film | membrane provided in the counter substrate side, (b) is an offset angle 0 degree, 1 degree, 2 degrees, 3 degrees, It is a figure which shows the relationship between the applied voltage when each set to 4 degrees, and the transmittance | permeability. (A) is a figure which shows a mode that the orientation direction is offset in the photo-alignment film | membrane provided in the TFT substrate side, (b) is an offset angle 0 degree, 1 degree, 2 degrees, 3 degrees, It is a figure which shows the relationship between the applied voltage when each set to 4 degrees, and the transmittance | permeability. (A) is a figure which shows a mode that the orientation direction is offset in each of the photo-alignment film | membrane provided in the TFT substrate side and the opposing substrate side, (b) is an offset angle 0 degree, 1 degree. It is a figure which shows the relationship between the applied voltage when set to 2 degrees, 3 degrees, and 4 degrees, respectively, and the transmittance | permeability. (A)-(c) is a top view for demonstrating operation | movement of the liquid crystal display device of another embodiment of this invention, (d)-(f) demonstrates operation | movement of the liquid crystal display device of a comparative example. It is a top view for doing. It is a figure which shows the relationship between the initial orientation direction of a liquid crystal molecule | numerator, a polarization axis direction, and a pixel electrode direction in the liquid crystal display device of the form shown to Fig.12 (a)-(c). It is sectional drawing which shows the structure of the liquid crystal display device of another embodiment of this invention. (A) And (b) is sectional drawing which shows the structure of the liquid crystal display device of another embodiment of this invention. (A) And (b) is a figure which shows the structure of the liquid crystal display device of another embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

  1 and 2 are enlarged views of a portion corresponding to one pixel of a liquid crystal display device according to an embodiment of the present invention. FIG. 1 is a plan view showing one pixel region of a TFT substrate 50 included in the liquid crystal display device, and FIG. 2 is a cross-sectional view taken along the line A-A ′ of FIG. 1.

  As shown in FIG. 2, the liquid crystal display device according to the present embodiment includes a TFT substrate 50 and a counter substrate 60 that are arranged to face each other, and a liquid crystal layer 70 that is held between them. Operate. The liquid crystal layer 70 includes a liquid crystal material having positive dielectric anisotropy, and a predetermined voltage is applied to a pair of electrodes (a common electrode 16 and a pixel electrode 18 described later) provided on the TFT substrate 50. Then, the display is performed by rotating the liquid crystal molecules in the substrate plane so as to align with the direction of the electric field.

  In each of the TFT substrate 50 and the counter substrate 60, a back side polarizing plate 29 and a front side polarizing plate 39 are disposed on the opposite side of the liquid crystal layer 70. In the liquid crystal display device of this embodiment, the absorption axis of the back-side polarizing plate 29 and the absorption axis of the front-side polarizing plate 39 (or the transmission axes thereof) are arranged in crossed Nicols so as to be orthogonal to each other. The liquid crystal display device of the present embodiment is a normally black mode liquid crystal display device that is in a black state when no voltage is applied.

  A backlight unit (not shown) configured using an LED, a cold cathode ray tube, or the like is provided outside the back-side polarizing plate 29, and light from the backlight unit is modulated by the liquid crystal layer 70. Display is performed.

  As shown in FIGS. 1 and 2, the TFT substrate 50 is provided in the vicinity of a transparent substrate 10 made of glass or the like, a gate bus line 2 provided on the transparent substrate 10, a source bus line 4, and an intersection thereof. TFT 6. The TFT 6 includes a gate electrode 12 connected to the gate bus line 2, a source electrode 14 connected to the source bus line 4, a drain electrode 15 provided to face the source electrode 14 at an interval, a source Typically, it is configured by an island-shaped semiconductor layer (not shown) connected to the electrode 14 and the drain electrode 15.

  The gate electrode 12, the source electrode 14, and the drain electrode 15 are electrically insulated by an intervening gate insulating film 20, and when an on-voltage is applied to the gate electrode 12, the source electrode 14 and the drain electrode 15. Are conducted through the semiconductor layer (channel).

The TFT 6, the source bus line 4, etc. are entirely covered with a first protective film (insulating film) 21 made of SiN _x or the like. An organic interlayer insulating film 24 is provided on the first protective film 21 to flatten the surface and prevent formation of unnecessary capacitance.

  A pixel PX is defined in a region surrounded by two adjacent gate bus lines 2 and two adjacent source bus lines 4. As shown in FIG. 2, in the pixel PX, the common electrode 16 formed over the entire organic interlayer insulating film 24 over the entire pixel PX and the second protective film (insulating film) 22 sandwich the common electrode 16. A pixel electrode 18 formed thereon is provided. Further, a photo-alignment film 28 is provided on the pixel electrode 18 so as to be in contact with the liquid crystal layer 70, and the alignment direction of the liquid crystal molecules LC when no voltage is applied is regulated by the photo-alignment film 28.

  Further, the pixel PX includes a first domain P1 and a second domain P2 that are adjacently disposed along the vertical direction (y-axis direction) in FIG. 1, and has a so-called dual domain configuration. In the present embodiment, the first domain P1 and the second domain P2 are symmetrically arranged with the pixel center line extending in the horizontal direction (x-axis direction) as an axis.

  The pixel electrode 18 provided for the pixel PX has a plurality of “<”-shaped electrode portions, that is, a plurality of bent elongated electrode portions (or a plurality of bent slits). This "<"-shaped electrode portion includes an elongated portion (first elongated portion) 181 extending in the first direction D3 and an elongated portion (second elongated portion) 182 extending in a direction D4 different from the first direction D3. It consists of. In the first domain P1, a plurality of first elongated portions 181 are arranged in parallel along a first direction D3 (sometimes referred to as an electrode direction D3), and in the second domain P2, a plurality of second elongated portions 182 are arranged. Are arranged in parallel along the second direction D4 (sometimes referred to as the electrode direction D4).

  The pixel electrode 18 including the first elongated portion 181 and the second elongated portion 182 is electrically connected to the drain electrode 15 of the TFT 6 through a contact hole (not shown). A signal voltage from the source bus line 4 is applied to the pixel electrode 18 while the TFT 6 is on. A common voltage is applied to the common electrode 16 independently of the pixel electrode 18 with a predetermined circuit configuration. Needless to say, the common electrode 16 is insulated from the pixel electrode 18 and the TFT 6.

  In the present embodiment, the common electrode 16 and the pixel electrode 18 are formed using a transparent conductive material such as ITO, and these are from a backlight unit (not shown) disposed on the back side of the TFT substrate 50. Can be transmitted. In addition, a storage capacitor (auxiliary capacitor) Cs connected in parallel with the liquid crystal capacitor Clc is formed in a portion where the common electrode 16 and the pixel electrode 18 face each other across the second protective film 22.

  In the TFT substrate 50 configured as described above, electric fields are generated in different directions in the first domain P1 and the second domain P2 in accordance with the voltages applied to the pixel electrode 18 and the common electrode 16. In the first domain P1, an electric field E1 having an in-plane component in a direction substantially orthogonal to the first elongated portion 181 is generated, and in the second domain P2, an in-plane component in a direction substantially orthogonal to the second elongated portion 182 is generated. An electric field E2 is generated. When a liquid crystal material having positive dielectric anisotropy is used, the liquid crystal molecules rotate in-plane so that the major axis direction is aligned with the direction of the generated electric field.

  The photo-alignment film 28 aligns liquid crystal molecules in different directions (first alignment direction D1 and second alignment direction D2 shown in FIG. 1) corresponding to each of the first domain P1 and the second domain P2. The first alignment region A1 and the second alignment region A2 are provided. The first alignment direction D1 and the second alignment direction D2 are, for example, more than 0 ° and 2 ° or less with respect to the absorption axis (absorption axis direction) AX1 (see FIG. 5) of the back-side polarizing plate 29 extending along the y-axis direction. It is set in a direction having a magnitude offset angle.

  More specifically, the first alignment direction D1 is set to a direction between the absorption axis direction (y-axis direction) and the direction D3 in which the first elongated portion 181 extends. The second alignment direction D2 is set to a direction between the absorption axis direction (y-axis direction) and the direction D4 in which the second elongated portion 182 extends. The first alignment direction D1 and the second alignment direction D2 are both directions different from the absorption axis direction, and are also different from the electrode directions D3 and D4.

  In the present specification, the “photo-alignment film” means an alignment film to which an alignment regulating force is imparted by irradiation with light (for example, polarized ultraviolet rays). Patent Document 2 describes a liquid crystal display device provided with a photo-alignment film. For example, an alignment film made of a polymer having a main chain of polyimide and a side chain containing a cinnamate group as a photoreactive functional group is disclosed. It describes that a photo-alignment film is formed by irradiating light.

  On the other hand, the counter substrate 60 includes a transparent substrate 30 made of glass or the like, a black matrix 32 provided on the transparent substrate 30, and red, green, and blue color filters 33R, 33G, and 33B. It corresponds to the display. On the liquid crystal layer 70 side of the transparent substrate 30, a photo-alignment film 38 is provided so as to be in contact with the liquid crystal layer 70 with the organic planarizing film 34 interposed therebetween. A transparent conductive film 36 made of ITO or the like is provided outside the transparent substrate 30 (on the side opposite to the liquid crystal layer side) to prevent charging.

  In the present embodiment, the photo-alignment film 38 provided on the transparent substrate 30 is disposed so as to correspond to the first domain P1 and the second domain P2, similarly to the photo-alignment film 28 provided on the TFT substrate 50 side. The first alignment region and the second alignment region are formed. The alignment direction in these alignment regions is set to be the same as that of the photo-alignment film 28 on the TFT substrate 50 side.

  However, as will be described later, one of the pair of photo-alignment films 28 and 38 disposed opposite to each other with the liquid crystal layer 70 interposed therebetween does not have a plurality of alignment regions and has a single alignment direction (typical) May be an alignment film having a direction parallel to the absorption axis of the polarizing plate. An alignment film having a single alignment direction can be easily produced by applying an alignment regulating force using a rubbing process.

  Hereinafter, the operation of the FFS mode liquid crystal display device having the dual domain configured as described above will be described together with the operation of the liquid crystal display device of the comparative example.

  3A to 3C show states of the liquid crystal display device according to the embodiment when no voltage is applied, when a low voltage is applied (for example, more than 0 V and not more than 1 V), and when a high voltage is applied (for example, more than 1 V). . 4A to 4C show states of the comparative liquid crystal display device when no voltage is applied, when a low voltage is applied, and when a high voltage is applied. For easy understanding of the drawing, the bent elongated electrode portion extending along the center of the pixel is omitted in FIGS. 3 (a) to 3 (c) and FIGS. 4 (a) to 4 (c).

  As shown in FIG. 3A, in the liquid crystal display device of this embodiment, the first domain P1 and the second domain P2 are positive and negative with respect to the absorption axis AX1 of the back-side polarizing plate 29 (here, The first orientation direction D1 and the second orientation direction D2 are respectively set so as to have an offset angle (with a clockwise angle being positive).

  FIG. 5 shows the orientation directions D1 and D2, the absorption axis of the back-side polarizing plate 29 (or the transmission axis of the front-side polarizing plate 39) AX1, and the absorption axis of the front-side polarizing plate 39 (or the transmission axis of the back-side polarizing plate 29) AX2. The relationship with the direction D3, D4 of the 1st and 2nd elongate electrode part (or slit in a pixel electrode) is shown. For easy understanding of the drawing, the bent elongated electrode portion extending in the center of the pixel is not shown in FIG.

  In the present embodiment, the extending direction D3 of the first elongated portion 181 in the first domain P1 is in a direction inclined by about 7 ° from the absorption axis AX1 of the back-side polarizing plate 29 (that is, has an offset angle β = 7 °). ) Is set. The offset angle α of the liquid crystal alignment direction D1 with respect to the absorption axis AX1 is set to about 1 °.

  Further, the extending direction D4 of the second elongated portion 182 in the second domain P2 is in a direction inclined by about −7 ° from the absorption axis AX1 of the back-side polarizing plate 29 (that is, has an offset angle β = −7 °). Is set. The offset angle α of the liquid crystal alignment direction D2 with respect to the absorption axis AX1 is set to about −1 °.

  When a voltage is applied, an electric field E1 having an in-plane component in a direction substantially perpendicular to the direction D3 of the first elongated portion 181 is generated in the first domain P1. The electric field E1 is actually generated as an oblique electric field having a component in the substrate vertical direction between the pixel electrode 18 and the common electrode 16. In the second domain P1, an electric field E2 having an in-plane component in a direction substantially perpendicular to the direction D4 of the second elongated portion 182 is generated. The electric field E2 is actually generated as an oblique electric field having a component in the substrate vertical direction between the pixel electrode 18 and the common electrode 16.

  When the relationship shown in FIG. 5 is satisfied, the liquid crystal molecules LC in the first domain P1 are rotated counterclockwise by the electric field E1 generated when a voltage is applied. Further, the liquid crystal molecules LC of the second domain P2 are rotated clockwise by the electric field E2 generated when a voltage is applied. That is, in the first domain P1 and the second domain P2, the rotation direction of the liquid crystal molecules when a voltage is applied is reversed.

  As described above, the first domain P1 and the second domain P2 have opposite rotation directions of the liquid crystal molecules when a voltage is applied. In any of the domains P1 and P2, the first alignment direction D1 and the second alignment direction are the same. D2 is set so as to have an angular offset with respect to the absorption axis AX1 in a direction opposite to the rotation direction of the liquid crystal molecules during voltage application.

  Reference is again made to FIGS. 3A to 3C and FIGS. 4A to 4C. As shown in FIG. 3A, in this embodiment, when no voltage is applied (or when 0 V is applied), the major axis directions of the liquid crystal molecules LC of the first domain P1 and the second domain P2 (that is, the first and second domains) Each alignment direction D1, D2) of the second alignment region is slightly inclined from the absorption axis (hereinafter sometimes referred to as a polarization axis) AX1. On the other hand, as shown in FIG. 4A, in the liquid crystal display device of the comparative example, the liquid crystal molecules LC in both the first domain P1 and the second domain P2 in the major axis direction (that is, typical) when no voltage is applied. Specifically, the single orientation direction D0) obtained by rubbing in one direction is parallel to the direction of the absorption axis AX1.

  Next, as shown in FIG. 3B, when a low voltage is applied between the pixel electrode 18 and the common electrode 16, in the liquid crystal display device of the embodiment, the first domain P1 and the second domain P2 In both cases, the major axis directions D1 ′ and D2 ′ of the liquid crystal molecules LC are parallel to the polarization axis AX1. On the other hand, as shown in FIG. 4B, in the liquid crystal display device of the comparative example, the major axis directions of the liquid crystal molecules in the first domain P1 and the second domain P2 are not parallel to the polarization axis AX1.

  Next, as shown in FIG. 3C, when a high voltage is applied between the pixel electrode 18 and the common electrode 16 when white display or the like is performed, in the liquid crystal display device of the embodiment, the first domain P1 and In both the second domains P2, the major axis directions D1 ′ and D2 ′ of the liquid crystal molecules LC rotate beyond the polarization axis AX1 and approach the directions of the electric fields E1 and E2. As shown in FIG. 4C, in the liquid crystal display device of the comparative example, the major axis directions of the liquid crystal molecules in the first domain P1 and the second domain P2 are closer to the directions of the electric fields E1 and E2.

  As described above, in the liquid crystal display device of the present embodiment, unlike the liquid crystal display device of the comparative example, the first domain is applied when a predetermined low voltage exceeding 0 V is applied, not when no voltage is applied. In both P1 and the second domain P2, the major axis directions D1 ′ and D2 ′ of the liquid crystal molecules LC and the polarization axis AX1 of the polarizing plate are in parallel, and the transmittance of the liquid crystal layer is minimized. That is, the transmittance becomes the lowest while the liquid crystal molecules LC are rotating in the domains P1 and P2 at the time of voltage application, not at the initial alignment, and black display can be performed when this transmittance is the lowest.

  In the liquid crystal display device of this embodiment, for example, when the liquid crystal display device is operated by the gate line inversion driving method described below, both low power consumption and suitable black display (contrast ratio) are achieved. be able to.

  6A schematically shows a circuit configuration corresponding to one pixel in this embodiment, and FIGS. 6B and 6C show driving signals (gate voltage Vg, data signal voltage) in gate line inversion driving. Vd, common voltage Vcom) and the like.

  The “gate line inversion driving method” is a driving method in which the polarity of the data signal voltage applied to each pixel is inverted for each adjacent gate line (or pixel row). The polarity is also inverted every frame. In this manner, by avoiding direct current drive, it is possible to prevent liquid crystal burn-in and the like and suppress deterioration of the liquid crystal display device.

  FIG. 6B shows a timing chart of each voltage in black display (black voltage) or low gradation (low voltage) in the FFS mode. The liquid crystal applied voltage VLC forms a small voltage difference between the data signal voltage (AC = source signal) VdAC and the common voltage VcomAC (AC) applied to the common electrode in the same phase, and is used as the liquid crystal applied voltage.

  Further, FIG. 6C shows a timing chart of each voltage in white display (high voltage). Since a high voltage difference is required at the time of white display, a high voltage difference is formed by shifting a half phase between the data signal voltage VdAC and the common voltage VcomAC, and a voltage VLC having a desired magnitude is applied to the pixel. In this way, power consumption can be suppressed by reducing the amplitude of the data signal voltage VdAC. For this reason, especially in applications where low power consumption is strongly desired, such as mobile applications, the data signal voltage and the common voltage may be driven with the polarity reversed.

  As shown in FIG. 6B, in the gate line inversion driving method, the polarity of the signal voltage (and the common voltage) is different for each gate line even in black display. However, in the normally black liquid crystal display device, the voltage applied to the liquid crystal layer (that is, the difference voltage between the signal voltage and the common voltage) is set to close to 0 V during black display.

  In order to realize low power consumption, it is conceivable to make either the data signal voltage or the common voltage smaller than the other even during black display. FIG. 6B shows a case where the common voltage VcomAC is set to be about 0.3 to 0.5 V lower than the data signal voltage VdAC. In this way, the power consumption can be further reduced by making the magnitudes of the voltages applied to the pixel electrode and the common electrode different during black display. However, in this driving method, a low voltage VLC of 0.3 to 0.5 V, which is a differential voltage, is applied to the liquid crystal layer even during black display.

  In a conventional dual domain FFS mode liquid crystal display device, the alignment direction of the liquid crystal (the rubbing direction of the alignment film) and the absorption axis direction of the polarizing plate are parallel so that the transmittance of the liquid crystal domain is minimized when 0 V is applied. Had been placed. Therefore, when a low voltage of about 0.3 to 0.5 V as described above is applied, the transmittance is not in a minimum state. Therefore, it is difficult to improve the contrast ratio by realizing an ideal black display while suppressing power consumption, and these have a trade-off relationship.

  On the other hand, when the above-described gate line inversion driving is used for driving the liquid crystal display device of this embodiment, black display is performed while reducing power consumption by applying a low voltage to the liquid crystal layer. This can be done in a state where the transmittance is minimized. In addition, in the dual domain configuration, the above-described effects can be obtained in any domain. In addition to realizing low power consumption and a high contrast ratio, color displacement when observed from an oblique direction can be suppressed, and display quality can be improved. Can be improved.

  6B and 6C also show a voltage VLC ′ (effective voltage applied to a predetermined pixel during one frame period) actually applied to the liquid crystal layer 70. This voltage VLC 'is affected by a feedthrough voltage (pull-in voltage) ΔVd generated when the TFT is switched off. The magnitude of the feedthrough voltage ΔVd is determined according to the magnitude of the gate-drain parasitic capacitance Cgd shown in FIG. Accordingly, the magnitude of the data signal voltage and the common voltage that are actually applied during black display is such that a predetermined low voltage is applied to the liquid crystal layer during the voltage holding period in consideration of the magnitude of the parasitic capacitance Cgd. It is preferable to select appropriately.

  In the TN (twisted nematic: normally white) mode, which is most popular in the liquid crystal display mode, it is common to drive white display (low voltage portion) in the vicinity of 0.3 to 1.0 V. . Since TN mode drive drivers are widely distributed and low in cost, by using the TN driver for the FFS mode, it is possible to reduce costs and to make parts common. Therefore, there is an advantage that a cost merit can be obtained by setting the black voltage in the FFS mode (normally black mode) to 0.3V to 1.0V instead of 0V.

  Hereinafter, a method for manufacturing a liquid crystal display device according to an embodiment of the present invention will be described.

  The portion of the TFT substrate 50 excluding the photo-alignment film 28 can be produced by a known method as in the conventional case. Further, the counter substrate 60 can be manufactured by a known method as in the prior art except for the alignment film 38. For this reason, the description of the manufacturing process of components other than the photo-alignment films 28 and 38 is omitted here.

Note that the gate insulating film 20, the first protective film 21, and the second protective film 22 of the TFT substrate 50 may be formed of a SiN _x film having a thickness of 0.2 μm to 0.5 μm, and a gate bus line. 2 and the source bus line 4 may be formed of a TiN / Al / TiN laminated metal film having a thickness of 0.4 μm. The organic interlayer insulating film 24 can be formed of an acrylic material having a thickness of 2.5 μm. Further, the pixel electrode 18 and the common electrode 16 can be formed of ITO having a thickness of 0.1 μm.

  The pixel electrode 18 includes a plurality of first and second elongated portions 181 and 182 extending in parallel in each of the domains P1 and P2, and the width thereof is set to, for example, about 0.1 μm. Further, the interval between the elongated portions 181 and 182 (or the width of the slit) can be set to, for example, about 4.0 μm. Further, the black matrix 32 of the counter substrate 60 can be formed of a black resin having a thickness of 1.6 μm, and the thickness of each color filter 33R, 33G, 33B is set to 1.5 μm. The organic planarization film 34 may be formed from an acrylic material having a thickness of 2.0 μm, and the transparent conductive film 36 for preventing charging may be formed from an ITO film having a thickness of 20 nm. The transparent conductive film 36 may be formed by a sputtering method after the liquid crystal injection process.

  Hereinafter, the manufacturing process of the photo-alignment films 28 and 38 will be described. In the present embodiment, in the photo-alignment films 28 and 38, two domains P1 and P2 are provided for each pixel, and the first alignment region and the first alignment region having different alignment directions so as to correspond to the domains P1 and P2 are provided. Two orientation regions are formed. Such an alignment film is produced as follows, for example.

  First, a material for the photo-alignment film is applied to the surface of the TFT substrate by a spin coat method or the like and baked to obtain a transparent resin film having a thickness of 0.06 to 0.08 μm, for example. More specifically, a photo-alignment film material (for example, an acrylic chalcone alignment film) is mixed in γ-butyrolactone so that the solid content concentration is about 3.0 wt%, and this is mixed with TFT / TFT installed in a spin coater. A counter coater is applied by adjusting the rotation speed of the spin coater so that the film thickness becomes 60 nm to 80 nm (for example, 1500 to 2500 rpm), and then the substrate is pre-baked on a hot plate (for example, at 80 ° C. for 1 minute). Then, a baking treatment is performed by post-baking (for example, at 180 ° C. for 1 hour).

Thereafter, as shown in FIG. 7, the photo-alignment film material is irradiated with linearly polarized ultraviolet light (polarized UV) having a polarization direction L1 through a mask 48 having a plurality of parallel slits 48S in a predetermined direction. A photo-alignment film is formed. More specifically, a mask 48 having a slit 48 s having a width of about 7 μm is disposed between the UV light source LS and the substrate (alignment film 28), and the irradiation energy is set to 1.5 J / cm ² and the polarized UV is emitted. It is carried out by irradiation. At this time, by using the UV light source LS and the slit mask 48, for example, by scanning the substrate along the predetermined direction DS at a speed of 35 μm / sec, the alignment process can be performed on the entire alignment film. In this embodiment, a photo-alignment film that exhibits liquid crystal alignment in a direction perpendicular to the irradiation direction of UV-polarized light (polarization direction L1) is used.

  At this time, the first alignment region (first domain P1) is irradiated with ultraviolet rays, and the second alignment region (second domain P2) is not irradiated with ultraviolet rays, so that the first alignment region is selected. In particular, it is possible to apply an alignment regulating force having a first alignment direction (a direction perpendicular to the polarization direction L1).

  Next, the second alignment region is irradiated with ultraviolet rays having a polarization direction different from that of the first alignment region by finely adjusting the angle between the mask 48 and the alignment film. Thereby, a photo-alignment film having different alignment directions in the first alignment region and the second alignment region is formed.

  8A and 8B show the relationship between the absorption axis AX1 of the back-side polarizing plate 29 and the UV polarization direction L1 and the electrode direction D3. Note that FIG. 8B shows only the relationship in the first domain P1 (or the first alignment region). As described above, the alignment direction D1 is defined in a direction perpendicular to the UV polarization direction L1, and this direction D1 is referred to as an offset angle α (referred to as a second offset angle) with respect to the absorption axis AX1 of the back-side polarizing plate 29. Direction). In addition, the second offset angle α is smaller than the offset angle β (sometimes referred to as a first offset angle) that the extending direction D3 of the elongated electrode portion (or slit) of the pixel electrode has with respect to the polarization axis AX1.

  The use of the photo-alignment film is advantageous because it is relatively easy to change the orientation direction for each domain by controlling the polarization direction of the ultraviolet rays irradiated using a mask having a slit or the like. By using the alignment film formed in this way, in a dual domain configuration, the major axis direction of the liquid crystal molecules in both domains can be made parallel to the polarization axis when a predetermined low voltage is applied.

  However, in order to obtain an alignment film having a different alignment direction for each domain, the photo-alignment film is not necessarily used. For example, a first alignment region is formed by rubbing in the first direction with the second domain covered with a resist, and then the first alignment region is covered with the resist after the resist of the second domain is removed. The second alignment region may be formed by rubbing in the second direction with the second domain exposed.

  After the TFT substrate 50 and the counter substrate 60 are manufactured, a liquid crystal panel is manufactured by sealing a liquid crystal material between the substrates. These panel manufacturing steps can also be performed by a known method. Hereinafter, a specific example will be described. First, a sealing material is applied to a peripheral portion of a region corresponding to one panel in the counter substrate 60 using a dispenser. As the sealing material, a thermosetting resin can be used.

  After applying the sealing material, a pre-baking step (for example, at 80 ° C. for 5 minutes) is performed. Further, spherical spacers having a desired diameter (3.3 μm in this embodiment) are dry-sprayed on the TFT substrate 50. Thereafter, the TFT substrate 50 and the counter substrate 60 are bonded together, and after performing a vacuum pressing process or a rigid pressing process, a post-baking process (for example, at 180 ° C. for 60 minutes) is performed.

  In addition, since a plurality of liquid crystal panels are usually formed on a single large mother glass, after the counter substrate 60 and the TFT substrate 50 are bonded together, a process of dividing into each panel is performed.

  In each panel, a gap is formed between the substrates in a state where the distance is maintained by the spacer, and a liquid crystal material is injected into the empty cell. The liquid crystal injection process is performed by putting an appropriate amount of liquid crystal material into an injection pan, setting it together with an empty cell in a vacuum chamber, and evacuating (for example, 60 minutes), followed by dip injection (for example, 60 minutes). After the cell into which the liquid crystal is injected is taken out of the chamber, the liquid crystal attached to the injection port is cleaned. Also, a UV curable resin is applied to the injection port, and this is cured by UV irradiation to seal the injection port, thereby completing the liquid crystal panel.

  In the liquid crystal panel thus manufactured, for example, birefringence Δn = 0.10, dielectric anisotropy Δε = 7.0, cell thickness d = 3.3 μm, and retardation dΔn = Set to 330 nm.

  Hereinafter, in a dual domain liquid crystal display device having a pixel electrode including a “<”-shaped electrode portion, application is performed when each initial alignment direction is shifted from the polarization axis of the polarizing plate while changing the initial alignment direction for each domain. The relationship between the voltage and the transmittance of the liquid crystal layer will be described based on the simulation result. The simulation results shown below were obtained by using a commercially available liquid crystal alignment simulator.

  9 to 11 show that the alignment direction of one or both of the photo-alignment films 28 on the TFT substrate 50 side and the photo-alignment film 38 on the counter substrate side is 1 ° with respect to the polarization axis. The relationship between the magnitude of the voltage applied to each liquid crystal layer and the transmittance when shifted from 0 ° to 4 ° in increments is shown. It is assumed that the elongated electrode portion of the pixel electrode is shifted by 7 ° with respect to the polarization axis.

  9A and 9B show a case where the alignment direction D1 and the polarization axis AX1 are shifted only in the photo-alignment film 38 on the counter substrate side. As can be seen from the figure, when the offset angle α is 0 ° (that is, the alignment direction and the polarization axis direction are parallel), the transmittance is minimized when 0 V is applied (or when no voltage is applied), as in the prior art. As the applied voltage increases, the transmittance also increases. On the other hand, when the offset angle α is set to 1 ° or more, it can be seen that the transmittance is minimized when a voltage exceeding 0 V is applied. Table 1 below shows the offset angle (second offset angle α), the corresponding contrast ratio, and the voltage Vtmin [V] when the minimum transmittance is achieved (when black is displayed). In this case, in order to realize a high contrast ratio (here, 500 or more), it is preferable to set the offset angle α to 1 ° or less. However, if the voltage Vtmin is greater than 0V, black display can be performed with a voltage greater than 0V, and this has the effect of reducing power consumption, particularly when operating with gate bus line inversion drive. can get. Therefore, in the present invention, the offset angle is not limited to 1 ° or less.

  The following second offset angle α is smaller than the offset angle of the elongated electrode portion with respect to the polarization axis (first offset angle) = 7 °. Therefore, the angle formed by the electric field direction and the initial alignment direction is smaller than 90 ° in the rotation direction (counterclockwise in the first domain) in the direction approaching the polarization axis. Thereby, the rotation direction of the liquid crystal molecules is controlled so as to rotate in the rotation direction approaching the polarization axis, that is, through a state parallel to the polarization axis. As a result, the first domain rotates counterclockwise and the second domain rotates clockwise.

  10A and 10B show a case where the alignment direction D1 and the polarization axis AX1 are shifted only in the photo-alignment film 28 on the TFT substrate side. As can be seen from the figure, when the offset angle α is 0 ° (that is, the alignment direction and the polarization axis direction are parallel), the transmittance is minimized when 0 V is applied (or when no voltage is applied), as in the prior art. As the applied voltage increases, the transmittance also increases. On the other hand, when the offset angle is set to 1 ° or more, it can be seen that the transmittance is minimized when a voltage exceeding 0 V is applied. Table 2 below shows the results of the offset angle, the corresponding contrast ratio, and the voltage Vtmin [V] when the minimum transmittance is achieved (when black is displayed). In this case, in order to realize a high contrast ratio (here, 500 or more), it is preferable to set the offset angle to 2 ° or less.

  11A and 11B show a case where the alignment direction D1 and the polarization axis AX1 are shifted in both the photo-alignment film 28 on the TFT substrate side and the photo-alignment film 38 on the counter substrate side. As can be seen from the figure, when the offset angle α is 0 ° (that is, the alignment direction and the polarization axis direction are parallel), the transmittance is minimized when 0 V is applied (or when no voltage is applied), as in the prior art. As the applied voltage increases, the transmittance also increases. On the other hand, when the offset angle is set to 1 ° or more, it can be seen that the transmittance is minimized when a voltage exceeding 0 V is applied. Table 3 below shows the results of the offset angle, the contrast ratio obtained correspondingly, and the voltage Vtmin [V] when the minimum transmittance is achieved (when black is displayed). In this case, in order to realize a high contrast ratio (here, 500 or more), it is preferable to set the offset angle to 1 ° or less.

  As described above, in at least one of the photo-alignment film 28 on the TFT substrate side and the photo-alignment film 38 on the counter substrate side, if the alignment direction has an offset angle with respect to the polarization axis, It was found that when a low voltage was applied, the transmittance was minimized and a high contrast ratio was obtained.

  In the above description, the case in which the extending direction D3 of the elongated portion (or slit) of the pixel electrode is deviated by 7 ° with respect to the polarization axis AX1, but this deviation angle (offset angle β) is 7 °. There is no need. The offset angle β is preferably 3 ° to 10 °.

  FIGS. 12A to 12F show a dual domain type liquid crystal display device according to another embodiment having different pixel electrode shapes, together with a liquid crystal display device of a comparative example. 12A to 12C show the liquid crystal display device of the present embodiment, and FIGS. 12D to 12F show the liquid crystal display device of the comparative example. FIG. 13 shows the relationship between the electrode direction, the polarization axis direction, and the alignment direction in more detail in the liquid crystal display device of this embodiment.

  As can be seen from FIG. 13, in the present embodiment, unlike the configuration shown in FIG. 3 and the like, the extending directions D3 and D4 of the elongated electrode portions 281 and 282 are not in the “<”-shaped electrode portion but in each domain. Have different “C” -shaped electrode portions. Such an electrode structure may be formed by providing a plurality of parallel elongated electrode portions in each domain by changing the inclination direction, or a single rectangular electrode covering both domains has different directions in both domains. You may form by providing a some parallel slit.

  Also in the present embodiment, in the alignment film (preferably a photo-alignment film), the first alignment region is provided for the first domain P1, and the second alignment region is provided for the second domain P2. In the first alignment region, liquid crystal molecules are aligned in the first alignment direction D1 when no voltage is applied, and in the second alignment region, liquid crystal molecules are aligned in the second alignment direction D2 when no voltage is applied. The first and second alignment directions D1 and D2 are directions different from each other and different from the polarization axis direction AX1 of the polarizing plate.

  In the present embodiment, the first alignment direction D1 is shifted by the second offset angle α counterclockwise in the first domain P1 with respect to the polarization axis (absorption axis of the back polarizing plate 29) AX1 extending in the horizontal direction of the drawing. In the second domain, the second orientation direction D2 is defined so as to be shifted clockwise by the second offset angle α. Also, the second offset angle α is smaller than the angle (first offset angle) β formed by the directions D3 and D4 in which the elongated electrode portions 281 and 282 extend with respect to the polarization axis AX1. Therefore, when a voltage is applied, in the first domain P1, the liquid crystal molecules LC rotate clockwise and become parallel to the polarization axis AX1 during the rotation. In addition, when a voltage is applied, in the second domain P2, the liquid crystal molecules LC rotate counterclockwise and become parallel to the polarization axis AX1 during the rotation. That is, when a voltage is applied, the liquid crystal molecules LC rotate in the opposite directions in the first domain P1 and the second domain P2, and all the liquid crystal molecules LC are parallel to the polarization axis AX1 during the rotation.

  FIGS. 12A to 12C show states when no voltage is applied (when 0 V is applied), when a low voltage is applied, and when a high voltage is applied, respectively, according to the present embodiment. These show states of the liquid crystal display device of the comparative example when no voltage is applied, when a low voltage is applied, and when a high voltage is applied.

  As can be seen from FIGS. 12A to 12C, in the liquid crystal display device of this embodiment, when no voltage is applied, the major axis directions of the liquid crystal molecules aligned in different directions D1 and D2 in the domains P1 and P2 are different. Although shifted from the polarization axis AX1, when a low voltage is applied, the major axis direction of the liquid crystal molecules becomes parallel to the polarization axis AX1, and the transmittance is minimized. Further, when a high voltage is applied, the liquid crystal molecules LC rotate so as to approach the directions of the electric fields E1 and E2 (directions perpendicular to the elongated electrode portions 281 and 281), and white display is performed.

  On the other hand, as can be seen from FIGS. 12D to 12F, in the liquid crystal display device of the comparative example, when no voltage is applied, the major axis direction of the liquid crystal molecules is parallel to the polarization axis AX1, and the transmittance is minimized. However, when a low voltage is applied, the long axis direction of the liquid crystal molecules is not parallel to the polarization axis AX1, so that the transmittance is not minimized. Furthermore, when a high voltage is applied, the liquid crystal molecules rotate so as to approach the electric field direction (direction perpendicular to the electrode portions 281 and 281), and the white display is performed as in the present embodiment.

  As described above, even in the form having the “C” -shaped pixel electrode portion, the liquid crystal display device of this embodiment can minimize the transmittance when applying a low voltage in each of the dual domains. When the liquid crystal display device is driven using the gate line inversion driving method, it is possible to achieve both reduction in power consumption and improvement in contrast ratio. On the other hand, in the apparatus of the comparative example, it is necessary to apply 0 V in order to take the state of minimum transmittance. Therefore, it is difficult to reduce power consumption, and black display cannot be stably performed. There is a fear.

  Even when a “C” -shaped pixel electrode is used, the initial orientation is larger than the angle (first offset angle β) formed by the direction in which the elongated portion (or slit) extends and the polarization axis direction of the polarizing plate. The angle formed by the direction and the polarization axis direction (second offset angle α) is preferably small. A preferable range of the second offset angle α is 1 ° to 2 °. In addition, the angle (first offset angle β) that the elongated directions D3 and D4 make with respect to the polarization axis AX1 is preferably 3 ° to 10 °.

  Also in the present embodiment, it is possible to set different orientation directions in the first domain P1 and the second domain P2 by changing the direction of the polarized UV light to be irradiated using the photo-alignment film. Further, as described with reference to FIGS. 9 to 11, if the alignment film having an alignment direction having an offset angle with respect to the polarization axis is provided on at least one of the TFT substrate 50 and the counter substrate 60. Good.

  As mentioned above, although embodiment of this invention was described, it cannot be overemphasized that other various modifications are possible. For example, as shown in FIG. 14, unlike the configuration shown in FIG. 2, the TFT substrate 52 is formed by providing the source bus line 4a (and the source electrode 14 and the drain electrode 15) in the same layer as the common electrode 16a. It may be configured. Further, as shown in FIG. 15, the TFT substrate is formed so that the source bus line 4b is formed in the same layer as the gate bus line 2 above the common electrode 16b (a layer between the common electrode 16b and the pixel electrode 18). 54 may be configured. In FIG. 14 and FIG. 15, the same components as those of the liquid crystal display device shown in FIG.

  In the above description, the dual domain type liquid crystal display device in which two domains (and two alignment regions) are formed for one pixel has been described. However, two domains are formed by two adjacent pixels. It may be. In this case, in one pixel, liquid crystal molecules are aligned in a first alignment direction having a predetermined offset angle with respect to the polarization axis to form one domain, and in the adjacent pixel, the first alignment direction is Differently, the liquid crystal molecules are aligned in a second alignment direction having a predetermined offset angle with respect to the polarization axis to form one domain. Even in such a configuration, when a voltage is applied between adjacent pixels, the liquid crystal molecules rotate reversely, and when a voltage exceeding 0 V is applied, the transmittance of each pixel (domain) can be minimized. Two pixels having different alignment directions (domains) may be arranged in the vertical direction or in the horizontal direction.

  Further, in the above description, a mode in which a positive type liquid crystal material having positive dielectric anisotropy is used has been described. However, a negative type liquid crystal material having negative dielectric anisotropy may be used. Also in this case, by appropriately setting the direction of the electrode and the orientation direction with respect to the polarization axis for each domain, a display that minimizes the transmittance when a low voltage is applied is performed while rotating the liquid crystal molecules in each domain in the reverse direction. Can be made.

  FIGS. 16 (a) and 16 (b) respectively show an application form to a "<"-shaped electrode structure and an application form to a "<"-shaped electrode structure when a negative type liquid crystal material is used. ing. As shown in FIGS. 16A and 16B, even when a negative liquid crystal material is used, the liquid crystal alignment directions D1 and D2 when 0 V is applied in the domains P1 and P2 are With respect to the absorption axis AX1, they are arranged so as to have a predetermined offset angle in the direction opposite to the liquid crystal rotation direction. With such a configuration, in each of the domains P1 and P2, when a low voltage is applied, the major axis direction of the liquid crystal molecules LC is parallel to the absorption axis AX1, and the transmittance can be minimized.

  In the above description, the liquid crystal molecule orientation direction and the absorption axis AX1 of the back side (backlight side) polarizing plate 29 are arranged substantially in parallel with an offset angle. It is not limited to any form. In another embodiment of the present invention, the alignment direction of the liquid crystal molecules may be arranged substantially in parallel with an offset angle with respect to the transmission axis of the back-side polarizing plate 29. Also in this case, the transmission axis of the front side polarizing plate 39 is arranged so as to be orthogonal to the transmission axis of the back side polarizing plate 29. In the present specification, the “polarization axis” may be either the absorption axis or the transmission axis. In the embodiment of the present invention, the alignment direction of the liquid crystal molecules is the polarization axis of the back side (or front side) polarizing plate. (Ie, either the absorption axis or the transmission axis) with an offset angle. The alignment direction of the liquid crystal molecules and the direction of the absorption axis (or transmission axis) of the polarizing plate are appropriately selected according to the display mode, the pixel electrode shape, and the like.

  Further, the present invention can also be applied to a dual domain IPS mode liquid crystal display device in which a pixel electrode and a common electrode are provided in the same layer.

  The present invention is widely used as a liquid crystal display device for mobile devices and TVs.

2 Gate bus line 4 Source bus line 6 TFT
10, 30 Glass substrate 12 Gate electrode 14 Source electrode 15 Drain electrode 16 Common electrode 18 Pixel electrode 28, 38 Photo-alignment film 29, 39 Polarizing plate 50 TFT substrate 60 Counter substrate 70 Liquid crystal layer D1 First alignment direction D2 Second alignment direction D3, D4 Pixel electrode direction AX1 Absorption axis (polarization axis) of back side polarizing plate
AX2 Absorption axis of the front-side polarizing plate (polarization axis)

Claims (12)

A liquid crystal layer; first and second substrates opposed to each other with the liquid crystal layer sandwiched therebetween; first and second polarizing elements respectively disposed on the first and second substrates; and a liquid crystal layer of the first substrate The first and second electrodes disposed on the side, and the first alignment film disposed on at least one liquid crystal layer side of the first substrate and the second substrate, wherein the liquid crystal molecules are aligned when no voltage is applied. A horizontal electric field mode liquid crystal display device comprising a first alignment film for regulating a direction,
The first alignment film includes a first alignment region for aligning the liquid crystal molecules in a first alignment direction, and an alignment of the liquid crystal molecules adjacent to the first alignment region in a second alignment direction different from the first alignment direction. A second alignment region to be
The first alignment direction and the second alignment direction are both directions different from the polarization axis direction of the first polarizing element,
When a voltage is applied between the first electrode and the second electrode, liquid crystal molecules in a first domain corresponding to the first alignment region and liquid crystal molecules in a second domain corresponding to the second alignment region Are rotated in opposite directions, and the major axis direction of the liquid crystal molecules in the first domain and the major axis direction of the liquid crystal molecules in the second domain are both in the direction of the polarization axis of the first polarizing element during the rotation. Liquid crystal display device parallel to   The first electrode includes a plurality of first electrode portions having an elongated shape, and the extending directions of the first electrode portions are different between the first domain and the second domain, and the first electrode and the first electrode The liquid crystal display device according to claim 1, wherein when a voltage is applied between two electrodes, directions of electric fields generated in the first domain and the second domain are different from each other.   The first domain and the second domain are included in one pixel, and the first electrode has a plurality of “<” shapes that are refracted at a boundary between the first domain and the second domain. The liquid crystal display device according to claim 2, further comprising an electrode portion.   The extending direction of the first electrode portion has a first offset angle with respect to the polarization axis direction, and the first and second alignment directions are first with respect to the polarization axis direction. 4. The liquid crystal display device according to claim 2, wherein the liquid crystal display device has an offset angle of 2, and the magnitude of the second offset angle is smaller than the magnitude of the first offset angle.   5. The first alignment film according to claim 1, wherein the first alignment film is a photo-alignment film, and the first and second alignment directions are determined according to a polarization direction of polarized light applied to the photo-alignment film. Liquid crystal display device. A backlight unit provided on the opposite side of the first polarizing element from the liquid crystal layer;
The liquid crystal display device according to claim 1, wherein the polarization axis of the first polarizing element is an absorption axis.   The liquid crystal display device according to claim 1, wherein the liquid crystal layer is made of a liquid crystal material having a positive dielectric anisotropy.   The liquid crystal layer further includes a second alignment film disposed so as to face the first alignment film, and the second alignment film is parallel to the first alignment direction of the first alignment film. A third alignment region for aligning liquid crystal molecules and a fourth alignment region for aligning liquid crystal molecules in a direction parallel to the second alignment direction, and the first alignment region and the second alignment of the first alignment film. The liquid crystal display device according to claim 1, wherein the region and the third alignment region and the fourth alignment region of the second alignment film are arranged to face each other.   The liquid crystal layer further includes a second alignment film disposed so as to face the first alignment film, and the second alignment film has a third alignment direction parallel to the polarization axis direction of the polarizing element. The liquid crystal display device according to claim 1, wherein liquid crystal molecules are aligned.   10. The liquid crystal display device according to claim 1, wherein the first and second alignment directions form an angle of greater than 0 ° to 2 ° with respect to the polarization axis direction.   11. The liquid crystal display device according to claim 1, wherein the liquid crystal display device operates in a gate line inversion driving system and a voltage exceeding 0 V is applied to the liquid crystal layer during black display.   The liquid crystal display device according to claim 1, wherein the first domain and the second domain are formed corresponding to two adjacent pixels, respectively.

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