JP2010160499A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device that excels in display quality and achieves a wider angle of field. <P>SOLUTION: The OCB type liquid crystal display device is provided with: a liquid crystal panel 1 which holds a liquid crystal layer 30 between one pair of substrates, has display pixels PX, and in which the liquid crystal molecules 31 of a liquid crystal layer 30 are bend-aligned in a predetermined state in which a voltage is applied to the liquid crystal layer 30; a driving means 60 applying a voltage corresponding to a display image to each display pixel PX of the liquid crystal panel 1; and an optical compensation element 40 which optically compensates for retardation of the liquid crystal layer 30 in which the liquid crystal molecules 31 are bend-aligned in the predetermined display state. The drive means 60 applies a voltage VD to each display pixel as a black voltage to be applied to the display pixel PX for displaying a black image, the voltage VD being set so as to have the lowest tristimulus value in a direction inclined with respect to the normal line of the liquid crystal panel 1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device having a configuration capable of suppressing gradation inversion in a screen.

  Usually, a color display device includes a red pixel that displays red, a green pixel that displays green, and a blue pixel that displays blue. In such a display device, the voltage-transmittance characteristics of these color pixels are set to be substantially equal and adjusted so as to display a natural color image with little color shift from the bright display area to the dark display area. Yes.

  Similarly, in a liquid crystal display device, a technique for displaying a color image with little color misregistration from a bright display area to a dark display area by independently setting voltages to be applied to each color pixel is disclosed (for example, (See Patent Document 1).

JP 2003-255908 A

  When gradation display is performed in the liquid crystal display device, the upper gradation is always displayed brighter than the lower gradation in the normal state. That is, the luminance (or transmittance) of the upper gradation is always high and the luminance (or transmittance) of the lower gradation is always high. On the other hand, the upper gradation may be displayed darker than the lower gradation. Such a phenomenon is called gradation inversion. When such gradation inversion occurs, the relationship between the brightness and gradation of the input video signal is inverted, resulting in a display defect.

  In recent years, OCB type liquid crystal display devices have attracted attention as liquid crystal display devices capable of improving the viewing angle and response speed. In such an OCB type liquid crystal display device, the viewing angle is normally compensated by canceling the birefringence amount by the bend alignment of the liquid crystal layer and the optical compensation element, thereby realizing a wide viewing angle. However, when the birefringence amount that should be canceled out becomes unbalanced due to a shift in the physical quantity of at least one of the liquid crystal layer and the optical compensation element, gradation inversion occurs.

  Further, when displaying a black image, a black voltage necessary for displaying the black image is applied to each display pixel. Normally, this black voltage is set so that the luminance in the front direction (that is, the normal direction of the liquid crystal display device) is minimized. However, when an imbalance that does not sufficiently offset the birefringence amount in the tilt direction tilted with respect to the normal line of the liquid crystal display device occurs, gradation inversion is visually observed when observed in the tilt direction. End up. For this reason, the display quality may be lowered, and the wide viewing angle may be hindered.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a liquid crystal display device that is excellent in display quality and capable of widening the viewing angle.

  A liquid crystal display device according to a first aspect of the present invention is configured to hold a liquid crystal layer between a pair of substrates, includes a display pixel, and a predetermined display in which liquid crystal molecules of the liquid crystal layer apply a voltage to the liquid crystal layer. A liquid crystal panel that bends in a state; drive means that applies a voltage corresponding to a display image to display pixels of the liquid crystal panel; and retardation of the liquid crystal layer in which liquid crystal molecules are bend in the predetermined display state. An OCB type liquid crystal display device comprising an optical compensation element that compensates automatically, wherein the driving means applies a normal voltage of the liquid crystal panel as a black voltage to be applied to a display pixel in order to display a black image. A voltage that is set so that a minimum tristimulus value is obtained in a tilt direction tilted with respect to the display pixel is applied to the display pixel.

  According to the present invention, it is possible to provide a liquid crystal display device that is excellent in display quality and capable of widening the viewing angle.

FIG. 1 is a cross-sectional view schematically showing a configuration of an OCB type liquid crystal display device as an embodiment of the present invention. FIG. 2 is a diagram schematically showing a configuration of an optical compensation element applied to the OCB type liquid crystal display device. FIG. 3 is a diagram showing the relationship between the optical axis direction and the liquid crystal alignment direction of each optical member constituting the optical compensation element shown in FIG. FIG. 4 is a diagram schematically showing a configuration for driving the liquid crystal display panel shown in FIG. FIG. 5 is a diagram illustrating an example of a relationship of luminance with respect to an applied voltage applied to a display pixel. FIG. 6 is a diagram illustrating an example of a relationship of transmittance with respect to an applied voltage applied to a display pixel. FIG. 7 is a diagram illustrating an example of the relationship of tristimulus values (Z values) to applied voltages applied to display pixels.

  Hereinafter, a liquid crystal display device according to an embodiment of the present invention and a black voltage setting method thereof will be described with reference to the drawings. In this embodiment, a liquid crystal display device using an OCB (Optically Compensated Bend) mode method will be described as an example of the liquid crystal display device. However, the present invention can also be applied to liquid crystal display devices in other display modes. Needless to say.

  As shown in FIG. 1, the OCB type liquid crystal display device includes a liquid crystal panel 1 having a liquid crystal layer 30 sandwiched between a pair of substrates, that is, an array substrate 10 and a counter substrate 20, and the liquid crystal panel 1 on the back surface. A backlight 50 for illuminating from is provided. The liquid crystal panel 1 is, for example, a transmission type, and is configured to be able to transmit backlight light from the backlight 50 arranged on the array substrate 10 side to the counter substrate 20 side. Further, the liquid crystal panel 1 includes an effective display unit 2 that substantially displays an image. The effective display unit 2 is composed of display pixels PX (R, G, B) arranged in a matrix.

  The array substrate 10 is formed using an insulating substrate 11 having optical transparency such as glass. The array substrate 10 includes a switch element 12, a pixel electrode 13, an alignment film 14 and the like on one main surface of an insulating substrate 11. The switch element 12 is disposed in each display pixel PX, and includes a TFT (Thin Film Transistor), a MIM (Metal Insulated Metal), or the like. The pixel electrode 13 is disposed in each display pixel PX and is electrically connected to the switch element 12. The pixel electrode 13 is formed of a light-transmitting conductive member such as ITO (Indium Tin Oxide). The alignment film 14 is disposed so as to cover the entire main surface of the insulating substrate 11, and is formed of a light transmissive material.

  The counter substrate 20 is formed using an insulating substrate 21 having optical transparency such as glass. The counter substrate 20 includes a counter electrode 22 and an alignment film 23 on one main surface of an insulating substrate 21. The counter electrode 22 is disposed in common in all the display pixels PX in the effective display portion 2, and is formed of a conductive member having light transmissivity, such as ITO. The alignment film 23 is disposed so as to cover the entire main surface of the insulating substrate 21 and is made of a light-transmitting material.

  In the color display type liquid crystal display device, the liquid crystal panel 1 displays a plurality of types of display pixels, for example, a red pixel PXR that displays red (R), a green pixel PXG that displays green (G), and blue (B). It has a blue pixel PXB. That is, the red pixel PXR includes a red color filter CFR that transmits light having a red main wavelength. The green pixel PXG includes a green color filter CFG that transmits light having a green main wavelength. The blue pixel PXB includes a blue color filter CFB that transmits light having a blue main wavelength. These color filters CF (R, G, B) are arranged on the main surface of the array substrate 10 or the counter substrate 20, but are arranged on the array substrate 10 in the example shown in FIG. 1.

  The array substrate 10 and the counter substrate 20 having the above-described configuration are arranged in a state where a predetermined gap is maintained with a spacer (not shown), and are bonded together by a sealing material. The liquid crystal layer 30 is sealed in the gap between the array substrate 10 and the counter substrate 20. The liquid crystal molecules 31 included in the liquid crystal layer 30 can be selected from materials having positive dielectric anisotropy and optically positive uniaxiality.

  Such an OCB type liquid crystal display device optically compensates for the retardation of the liquid crystal layer 30 including the liquid crystal molecules 31 bend-aligned as shown in FIG. 1 in a predetermined display state in which a voltage is applied to the liquid crystal layer 30. An optical compensation element 40 is provided. As shown in FIG. 2, the optical compensation element 40 includes a first compensation element 40A disposed on one main surface of the liquid crystal panel 1, that is, the outer surface on the array substrate 10, and the other main surface of the liquid crystal panel 1, that is, a counter substrate. And a second compensation element 40B disposed on the outer surface of the 20 side.

  For example, the first compensation element 40A includes a polarizing plate 41A and a plurality of optical elements 42A and 43A that function as retardation plates. Similarly, the second compensation element 40B includes a polarizing plate 41B and a plurality of optical elements 42B and 43B that function as retardation plates. The optical elements 42A and 42B mainly function as retardation plates having retardation (phase difference) in the thickness direction. The optical elements 43A and 43B mainly function as retardation plates having retardation (phase difference) in the in-plane direction.

  As shown in FIG. 3, the alignment films 14 and 23 have been subjected to parallel alignment processing (that is, have been rubbed in the direction indicated by the arrow A in the figure). Thereby, the orthogonal projection (liquid crystal alignment direction) of the optical axis of the liquid crystal molecules 31 is parallel to the arrow A in the figure. In a state where an image can be displayed, that is, in a state where a predetermined bias is applied, the liquid crystal molecules 31 are arranged in the cross section of the liquid crystal layer 30 defined by the arrow A as shown in FIG. A bend arrangement between 20 and 20.

  At this time, the polarizing plate 41A is arranged so that its transmission axis faces the direction indicated by the arrow B in the drawing. Further, the polarizing plate 41B is arranged so that the transmission axis thereof faces the direction indicated by the arrow C in the drawing. That is, the transmission axes of the polarizing plates 41A and 41B form an angle of 45 ° with respect to the liquid crystal alignment direction A, and are orthogonal to each other. In this way, the arrangement in which the transmission axes of the polarizing plates are orthogonal to each other is called crossed Nicol, and the birefringence amount (retardation amount) of the object between the pair of polarizing plates is effectively 0 or an integral multiple of the wavelength. Light is not transmitted and a black image is displayed. Conversely, if the birefringence amount (retardation amount) of the object between the pair of polarizing plates is effectively λ / 2 with respect to the incident light having the wavelength λ, the light is transmitted and a white image (or color image) is displayed. Is done.

  The optical elements 43A and 43B compensate for the influence of retardation remaining in the liquid crystal layer 30 when the screen is observed from the front direction in a specific voltage application state (for example, a state where a high voltage is applied to display a black image). . The optical elements 42A and 42B compensate for the influence of retardation of the liquid crystal layer 30 when the screen is observed from an oblique direction in a specific voltage application state (for example, a state where a high voltage is applied to display a black image). . As a result, viewing angle characteristics and display quality can be improved in the OCB type liquid crystal display device.

  As shown in FIG. 4, the liquid crystal display device applies a voltage corresponding to a display image to each display pixel PX (R, G, B) of the liquid crystal panel 1 having the above-described configuration (supplying a video signal). A panel driving unit 60 functioning as a driving unit.

  That is, the panel drive unit 60 is electrically connected to the liquid crystal panel 1 via a flexible printed circuit board or the like. The panel driving unit 60 can display the red pixel PXR, the green pixel PXG, and the blue pixel PXB with optimal brightness for each gradation of the display image based on the input video data. Apply an optimized voltage.

  More specifically, since the voltage applied to the counter electrode 22 is common to each display pixel, the panel driving unit 60 optimizes the voltage applied to the pixel electrode 13. The panel driving unit 60 outputs the voltage VR set for the red pixel when the switch element 12 of the red pixel PXR is turned on, and sets the voltage VR for the green pixel when the switch element 12 of the green pixel PXG is turned on. The voltage VG is output, and the voltage VB set for the blue pixel is output at the timing when the switch element 12 of the blue pixel PXB is turned on. Each voltage V (R, G, B) output from the panel drive unit 60 is written to the pixel electrode 13 from the corresponding signal line X via the switch element 12.

Example 1
In the OCB type liquid crystal display device described above, the luminance of the display pixel PX has a characteristic as shown in FIG. 5 with respect to the applied voltage applied to the display pixel PX. That is, in the OCB type liquid crystal display device, the applied voltage-luminance characteristic in the front direction (that is, the normal line direction of the liquid crystal display device) decreases as the applied voltage increases, as indicated by A in the figure. However, once it reaches the minimum luminance, it increases again. For this reason, the black voltage to be applied to the display pixels in order to display a black image is set to an applied voltage that provides the lowest luminance based on the applied voltage-luminance characteristics in the front direction.

  However, in the black voltage setting method as described above, when the amount of birefringence that should be canceled out becomes unbalanced due to a shift in the physical quantity of at least one of the liquid crystal layer 30 and the optical compensation element 40, the grayscale level is reduced in the front direction. The inversion is not visually recognized, but the gradation inversion may be visually recognized in the inclination direction inclined with respect to the normal line.

  That is, such a phenomenon compares the applied voltage-luminance characteristics in the front direction as shown by A in FIG. 5 with the applied voltage-luminance characteristics in the tilt direction as shown in B of FIG. When the latter is shifted to a lower level, it appears. In other words, the applied voltage VB having the lowest luminance in the tilt direction is shifted to a lower level than the applied voltage VA having the lowest luminance in the front direction. For this reason, when the applied voltage VA is set as a black voltage, the applied voltage (for example, VB) corresponding to the higher gradation is applied when the applied voltage (for example, VA) corresponding to the lower gradation is applied in the tilt direction. The luminance becomes higher than that when the voltage is applied, and gradation inversion occurs.

  Therefore, in the first embodiment, the panel driving unit 60 uses a voltage set to have the lowest luminance in the tilt direction as the black voltage to be applied to the display pixel PX in order to display a black image. Apply to. In the first embodiment, the black voltage is set by the following method.

  That is, the luminance of the display pixel PX with respect to the applied voltage applied to the display pixel PX is measured using the inclination θ with respect to the normal line of the liquid crystal panel 1 as a parameter. Thereby, measurement results such as A and B of FIG. 5 are obtained. Here, each applied voltage-luminance characteristic was measured in the range of the maximum viewing angle (for example, θ = 60 °) in which the liquid crystal display panel 1 can be observed from the normal direction (θ = 0 °).

  Then, based on the respective applied voltage-luminance characteristics obtained by measurement, the lowest applied voltage among the applied voltages with the lowest luminance is set as the black voltage of the display pixel. In the example shown in FIG. 5, as the inclination with respect to the normal increases, the applied voltage that provides the lowest luminance tends to shift to a lower level. When such a tendency is exhibited, an applied voltage (for example, VB) that provides the lowest luminance in the tilt direction corresponding to the maximum viewing angle is set as the black voltage.

  The panel driving unit 60 applies the black voltage set in this way to each display pixel PX when displaying the image of the lowest gradation. This makes it possible to suppress gradation inversion in all viewing angle directions, improving display quality and widening the viewing angle.

  In addition, the panel driving unit 60 can apply voltages that are set independently to each color pixel PX (R, G, B) so as to correspond to the display image. Therefore, in the first embodiment, an optimum black voltage is set for each color pixel PX (R, G, B) by the method described above. That is, for the red pixel PXR, the applied voltage that provides the lowest luminance in the tilt direction is set as the black voltage VR. Similarly, for the green pixel PXG, the applied voltage having the lowest luminance in the inclination direction is set as the black voltage VG, and for the blue pixel PXB, the applied voltage having the lowest luminance in the inclination direction is set as the black voltage VB.

  The panel driving unit 60 applies the black voltage set in this way to each color pixel PX (R, G, B) when displaying the image of the lowest gradation. As a result, gradation inversion can be suppressed in all viewing angle azimuths of the respective color pixels PX (R, G, B), display quality can be improved, and a wide viewing angle can be achieved.

(Example 2)
In an OCB type liquid crystal display device or the like, the transmittance of a display pixel PX that transmits light in a predetermined wavelength region has a characteristic as shown in FIG. 6 with respect to an applied voltage applied to the display pixel PX. That is, in the OCB type liquid crystal display device, the applied voltage-transmittance characteristics at a predetermined wavelength, as indicated by λ1 in the figure, the transmittance decreases as the applied voltage increases, and once reaches the minimum transmittance. After that increase again.

  For this reason, when the black voltage to be applied to the display pixel in order to display a black image is set to the applied voltage that provides the minimum transmittance based on the applied voltage-transmittance characteristics at a predetermined wavelength, in the liquid crystal display device Grayscale inversion does not necessarily occur in the entire wavelength region where display is possible. For example, the green pixel PXG transmits light in a wavelength region of 500 nm to 600 nm. At this time, an applied voltage-transmittance characteristic at a wavelength of 600 nm as shown by λ1 in FIG. 6, an applied voltage-transmittance characteristic at a wavelength of 550 nm as shown by λ2, and a wavelength of 500 nm as shown by λ3. When comparing the applied voltage-transmittance characteristic at, the characteristic indicated by λ3 is shifted to a lower level. For each wavelength, when the applied voltage-transmittance characteristics are compared between the front direction and the tilt direction, the characteristics in the tilt direction are shifted to a lower level as in the first embodiment. , The characteristics of each wavelength are examined in the same inclination direction.

  That is, the applied voltage Vλ2 that provides the minimum transmittance at a wavelength of 550 nm is shifted to a lower level than the applied voltage Vλ1 that provides the minimum transmittance at a wavelength of 600 nm. In addition, the applied voltage Vλ3 having the lowest transmittance at the wavelength of 500 nm is shifted to a lower level than the applied voltage Vλ2 having the lowest transmittance at the wavelength of 550 nm.

  For this reason, when the applied voltage Vλ1 is set as a black voltage, when the applied voltage (for example, Vλ1) corresponding to the lower gradation is applied to light having a wavelength other than the wavelength of 600 nm, particularly light having a wavelength shorter than 600 nm, The transmittance becomes higher than when an applied voltage (for example, Vλ2 or Vλ3) corresponding to the gradation is applied, and gradation inversion occurs.

  Therefore, in the second embodiment, the panel driving unit 60 uses the lowest wavelength light in the predetermined wavelength region as the black voltage to be applied to the display pixel PX in order to display a black image. A voltage set so as to have transmittance is applied to the display pixel PX. In the second embodiment, the black voltage is set by the following method.

  That is, the transmittance of the display pixel PX with respect to the applied voltage applied to the display pixel PX is measured in the tilt direction of the predetermined tilt θ with respect to the normal line of the liquid crystal panel 1 using the wavelength in the predetermined wavelength region as a parameter. Thereby, measurement results such as λ1 to λ3 in FIG. 6 are obtained. Here, the applied voltage-transmittance characteristics were measured for each wavelength in the wavelength region where the display pixel PX can transmit.

  Then, based on the respective applied voltage-transmittance characteristics obtained by measurement, the lowest applied voltage among the applied voltages having the lowest transmittance is set as the black voltage of the display pixel. In the example shown in FIG. 6, there is a tendency that the applied voltage at which the minimum transmittance becomes lower as the wavelength is shorter in the predetermined wavelength region. When such a tendency is exhibited, an applied voltage (for example, Vλ3) at which the light having the shortest wavelength in the predetermined wavelength region has the lowest transmittance is set as the black voltage.

  The panel driving unit 60 applies the black voltage set in this way to each display pixel PX when displaying the image of the lowest gradation. This makes it possible to suppress gradation inversion in all viewing angle directions and in all wavelength regions, improving display quality and widening the viewing angle.

  In addition, the panel driving unit 60 can apply voltages that are set independently to each color pixel PX (R, G, B) so as to correspond to the display image. Therefore, in the second embodiment, an optimum black voltage is set for each color pixel PX (R, G, B) by the method described above. That is, for the red pixel PXR, for example, light having a wavelength range of 580 nm to 610 nm can be transmitted, and the applied voltage at which the shortest wavelength light within this wavelength range has the lowest transmittance is set as the black voltage VλR. Similarly, for the green pixel PXG, as in the example described above, for example, light having a wavelength region of 500 nm to 600 nm can be transmitted, and an applied voltage at which the shortest wavelength light in this wavelength region has the lowest transmittance is set. Set as black voltage VλG. For the blue pixel PXB, for example, light having a wavelength region of 430 nm to 580 nm can be transmitted, and an applied voltage at which the shortest wavelength light in this wavelength region has the lowest transmittance is set as the black voltage VλB.

  The panel driving unit 60 applies the black voltage set in this way to each color pixel PX (R, G, B) when displaying the image of the lowest gradation. This makes it possible to suppress gradation inversion in the entire viewing angle azimuth of each color pixel PX (R, G, B) and in all wavelength regions, improving the display quality and widening the viewing angle. It becomes possible.

(Example 3)
In an OCB type liquid crystal display device or the like, in the XYZ color system, the tristimulus value Z of the display pixel PX has characteristics as shown in FIG. 7 with respect to the applied voltage applied to the display pixel PX. In Example 3, the basis for focusing on the Z value, which is one of the tristimulus values, is based on the fact that the Z value is shorter in wavelength than the X value and the Y value, and has higher sensitivity.

  In other words, in the OCB type liquid crystal display device, the applied voltage-tristimulus value (Z) characteristic in the front direction decreases as the applied voltage increases, as indicated by C in the figure. Once it reaches the minimum Z value, it increases again. For this reason, when the black voltage to be applied to the display pixel in order to display the black image is set to the applied voltage that is the lowest Z value based on the applied voltage-tristimulus value (Z) characteristic in the front direction, The gradation inversion does not necessarily occur in all wavelength regions and all viewing angle directions that can be displayed in a liquid crystal display device.

  For example, the applied voltage-tristimulus value (Z) characteristic in the front direction as shown by C in FIG. 7 and the applied voltage-tristimulus value (Z) characteristic in the inclination direction as shown by D are shown in FIG. When compared, the latter is shifted to a lower level. That is, the applied voltage VC having the lowest Z value in the tilt direction is shifted to a lower level than the applied voltage VC having the lowest Z value in the front direction. For this reason, when the applied voltage VC is set as a black voltage, when an applied voltage (for example, VC) corresponding to the lower gradation is applied in the inclination direction, an applied voltage (for example, VD) corresponding to the higher gradation is applied. The Z value becomes higher than when the voltage is applied, and gradation inversion occurs.

  Therefore, in the third embodiment, the panel driving unit 60 displays the voltage set to the lowest Z value in the tilt direction as the black voltage to be applied to the display pixel PX in order to display the black image. Apply to PX. In the third embodiment, the black voltage is set by the following method.

  That is, the tristimulus value (Z) of the display pixel PX with respect to the applied voltage applied to the display pixel PX is measured using the inclination θ with respect to the normal line of the liquid crystal panel 1 as a parameter. As a result, measurement results such as C and D in FIG. 7 are obtained. Here, each applied voltage-tristimulus value (Z) characteristic is measured in the range of the maximum viewing angle (for example, θ = 60 °) in which the liquid crystal display panel 1 can be observed from the normal direction (θ = 0 °). did.

  Then, based on the respective applied voltage-tristimulus value (Z) characteristics obtained by the measurement, the lowest applied voltage among the applied voltages having the lowest Z value is set as the black voltage of the display pixel. In the example shown in FIG. 7, the applied voltage that is the lowest Z value tends to shift to a lower level as the inclination with respect to the normal increases. When such a tendency is exhibited, an applied voltage (for example, VD) that sets the lowest Z value in the tilt direction corresponding to the maximum viewing angle is set as the black voltage.

  The panel driving unit 60 applies the black voltage set in this way to each display pixel PX when displaying the image of the lowest gradation. This makes it possible to suppress gradation inversion in all viewing angle directions and in all wavelength regions, improving display quality and widening the viewing angle.

  In addition, the panel driving unit 60 can apply voltages that are set independently to each color pixel PX (R, G, B) so as to correspond to the display image. Therefore, in the third embodiment, an optimum black voltage is set for each color pixel PX (R, G, B) by the method described above. That is, for the red pixel PXR, the applied voltage that has the lowest Z value in the tilt direction is set as the black voltage VR. Similarly, for the green pixel PXG, the applied voltage having the lowest Z value in the tilt direction is set as the black voltage VG, and for the blue pixel PXB, the applied voltage having the lowest Z value in the tilt direction is set as the black voltage VB.

  The panel driving unit 60 applies the black voltage set in this way to each color pixel PX (R, G, B) when displaying the image of the lowest gradation. This makes it possible to suppress gradation inversion in the entire viewing angle azimuth of each color pixel PX (R, G, B) and in all wavelength regions, improving the display quality and widening the viewing angle. It becomes possible.

  As described above, according to this embodiment, among the voltages applied to the display pixels, the black voltage necessary for displaying the black image is in the entire viewing angle direction, and the luminance of the lower gradation is the upper gradation. It is set so that it does not exceed the luminance of. Also, among the voltages applied to the display pixels, the black voltage necessary for displaying a black image is lower than the upper grayscale transmittance in the entire viewing angle azimuth and all visible wavelength regions. It is set not to exceed. Further, among the voltages applied to the display pixels, the black voltage necessary for displaying the black image is the tristimulus value Z of the lower gradation in the entire viewing angle direction and the entire visible wavelength region, and the tristimulus value of the upper gradation. It is set so as not to exceed Z.

  Even when the amount of birefringence that should be canceled out by such voltage setting becomes unbalanced due to a shift in the physical quantity of at least one of the liquid crystal layer and the optical compensation element, the gradation is observed when observed in the tilt direction. Inversion can be suppressed. Therefore, display quality can be improved and a wide viewing angle can be achieved.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the spirit of the invention in the stage of implementation. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine the component covering different embodiment suitably.

  DESCRIPTION OF SYMBOLS 1 ... Liquid crystal panel, 2 ... Effective display part, 10 ... Array board | substrate, 20 ... Opposite board | substrate, 30 ... Liquid crystal layer, 31 ... Liquid crystal molecule, 40 ... Optical compensation element, 50 ... Back light, 60 ... Panel drive part.

Claims (3)

A liquid crystal panel configured to hold a liquid crystal layer between a pair of substrates, provided with display pixels, and in which a liquid crystal molecule of the liquid crystal layer bends in a predetermined display state in which a voltage is applied to the liquid crystal layer;
Drive means for applying a voltage corresponding to a display image to display pixels of the liquid crystal panel;
An optical compensation element that optically compensates for retardation of the liquid crystal layer in which liquid crystal molecules are bend-aligned in the predetermined display state;
An OCB type liquid crystal display device comprising:
The driving means displays a voltage set to be a minimum tristimulus value in a tilt direction inclined with respect to the normal line of the liquid crystal panel as a black voltage to be applied to a display pixel in order to display a black image. A liquid crystal display device which is applied to a pixel. The display pixel includes a red pixel, a green pixel, and a blue pixel,
The driving means is configured to independently set a black voltage to be applied to the red pixel, a black voltage to be applied to the green pixel, and a black voltage to be applied to the blue pixel. Item 2. A liquid crystal display device according to item 1.   The liquid crystal display device according to claim 1, wherein the tilt direction is a direction tilted by 60 ° with respect to a normal line of the liquid crystal panel.

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