Liquid crystal display device

Abstract

Provided is a liquid crystal display device capable of switching between a privacy mode and a public mode and suppressing changes in brightness and hue of a liquid crystal panel in the privacy mode and the public mode. A liquid crystal display device according to the present invention includes a liquid crystal panel having a first electrode and a second electrode on a substrate, a second substrate having a third electrode, and a control unit for driving the liquid crystal panel, the control unit having a display mode switching unit, a gamma correction table storage unit, a gamma correction unit, and an image data output unit, the display mode switching unit performs switching between a narrow viewing angle mode and a wide viewing angle mode by controlling a voltage applied to the third electrode, the gamma correction table storage unit stores a gamma correction table in which a gradation value is associated with a voltage applied to the first electrode and / or the second electrode, and the gamma correction unit stores a gamma correction table in which the gradation value is associated with the voltage applied to the first electrode and / or the second electrode in the narrow viewing angle mode and the wide viewing angle mode. Different gamma correction tables are acquired from a gamma correction table storage unit, and gamma correction is performed on the basis of each gamma correction table.

Description

Technical Field

[0001] The present disclosure relates to a liquid crystal display device. Background Art

[0002] Liquid crystal display devices are display devices that use liquid crystal compositions for display purposes. A typical display method is to apply a voltage to a liquid crystal composition sealed between a pair of substrates, and change the orientation state of liquid crystal molecules in the liquid crystal composition according to the applied voltage, thereby controlling the amount of light transmitted. Such liquid crystal display devices are used in a wide range of fields by making full use of their advantages such as thinness, lightness, and low power consumption.

[0003] In the past, liquid crystal display devices have been studied to improve viewing angle characteristics so that the same image can be observed whether it is observed from a narrow viewing angle range or a wide viewing angle range. On the other hand, from the perspective of maintaining privacy, a display method that can observe an image from a narrow viewing angle range but is difficult to observe from a wide viewing angle range has been studied. For example, Patent Document 1 discloses a liquid crystal display device that can switch between a narrow viewing angle mode and a wide viewing angle mode by controlling a voltage applied to a third electrode provided on a color filter substrate. Prior art literature Patent Literature

[0004] Patent Document 1: Japanese Patent Application Publication No. 2021-67852 Summary of the invention Technical Problems to be Solved by the Invention

[0005] According to the inventors' research, when the public mode and the private mode are switched by applying a voltage to the third electrode disposed on the counter substrate side, the front brightness and color tone of the liquid crystal panel may be different between the public mode and the private mode.

[0006] The present invention has been made in view of the above-mentioned current situation, and an object of the present invention is to provide a liquid crystal display device which can switch between a private mode and a public mode and suppresses changes in brightness and color tone of a liquid crystal panel in the private mode and the public mode. Solutions for solving problems

[0007] (1) One embodiment of the present invention is a liquid crystal display device, which includes a liquid crystal panel and a control unit that drives the liquid crystal panel, wherein the liquid crystal panel has a first substrate, a liquid crystal layer, and a second substrate in sequence, the first substrate having a first electrode and a second electrode stacked with a first insulating layer therebetween, or having a first electrode and a second electrode arranged opposite to each other, and the second substrate having a third electrode, the control unit having a display mode switching unit, a gamma correction table storage unit, a gamma correction unit, and an image data output unit, the display mode switching unit switches between a narrow viewing angle mode and a wide viewing angle mode by controlling a voltage applied to the third electrode, the gamma correction table storage unit stores a gamma correction table that associates a grayscale value with a voltage applied to the first electrode and / or the second electrode, the gamma correction unit obtains different gamma correction tables from the gamma correction table storage unit in the narrow viewing angle mode and the wide viewing angle mode, performs gamma correction on original image data based on each gamma correction table, and outputs the obtained gamma-corrected image data to the image data output unit, the image data output unit outputs a liquid crystal panel driving signal to the liquid crystal panel to adjust the voltage applied to the first electrode and / or the second electrode.

[0008] (2) In addition, in a liquid crystal display device according to a certain embodiment of the present invention, based on the configuration of (1) above, the difference between the gamma value of the gamma correction table used in the narrow viewing angle mode and the gamma value of the gamma correction table used in the wide viewing angle mode is less than 0.4.

[0009] (3) In addition, in a liquid crystal display device according to a certain embodiment of the present invention, based on the configuration of (1) or (2) above, the gamma value of the gamma correction table used in the narrow viewing angle mode is smaller than the gamma value of the gamma correction table used in the wide viewing angle mode.

[0010] (4) In a liquid crystal display device according to an embodiment of the present invention, in addition to the configuration of any one of (1) to (3) above, the gamma correction table storage unit includes a gamma correction table in which the gamma value is constant between grayscales 0 to 255.

[0011] (5) In a liquid crystal display device according to an embodiment of the present invention, based on any one of the configurations (1) to (3) above, the gamma correction table storage unit includes a gamma correction table having a plurality of gamma values ​​between grayscales 0 and 255.

[0012] (6) In addition, in a liquid crystal display device of a certain embodiment of the present invention, based on the structure of (4) or (5) above, the gamma value of the gamma correction table used in the wide viewing angle mode is constant between grayscales 0 and 255, and the gamma value of the gamma correction table used in the narrow viewing angle mode has multiple values ​​between grayscales 0 to 255.

[0013] (7) In addition, in a liquid crystal display device of a certain embodiment of the present invention, based on the structure of the above (6), when any grayscale between 0 and 255 is set as grayscale X, in the grayscale greater than 0 (≥0) and less than X, the gamma value of the gamma correction table used in the narrow viewing angle mode is smaller than the gamma value of the gamma correction table used in the wide viewing angle mode, and in the grayscale greater than X and less than 255, the gamma value of the gamma correction table used in the narrow viewing angle mode is greater than the gamma value of the gamma correction table used in the wide viewing angle mode.

[0014] (8) In addition, in a liquid crystal display device according to a certain embodiment of the present invention, based on the configuration of (6) above, when any grayscale between 0 and 255 is set to X and any grayscale greater than X is set to Y, in the grayscale greater than 0 and less than X, the gamma value of the gamma correction table used in the narrow viewing angle mode is smaller than the gamma value of the gamma correction table used in the wide viewing angle mode, and in the grayscale greater than Y and less than 255, the gamma value of the gamma correction table used in the narrow viewing angle mode is larger than the gamma value of the gamma correction table used in the wide viewing angle mode.

[0015] (9) In addition, in a liquid crystal display device of a certain embodiment of the present invention, based on the structure of any one of the above (1) to (8), at least one of the first electrode and the second electrode includes a linear electrode portion configured for each pixel and extending in a first direction, and the third electrode includes a linear electrode portion extending in a second direction intersecting the first direction when viewed from above. Effects of the Invention

[0016] According to the present invention, it is possible to provide a liquid crystal display device capable of switching between a private mode and a public mode, and in which changes in brightness and color tone of a liquid crystal panel are suppressed in the private mode and the public mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a block diagram showing an example of a display method of the liquid crystal display device according to the embodiment. Figure 2 1 is a schematic plan view showing an example of a liquid crystal display device according to the first embodiment. Figure 3 yes Figure 2 A schematic top view of a pixel of a liquid crystal display device is shown. Figure 4 It is along Figure 2 A schematic cross-sectional view of line Y1-Y2. Figure 5 It is along Figure 2 A schematic cross-sectional view of line X1-X2. Figure 6 This is a three-dimensional diagram of the structure around the liquid crystal panel. Figure 7 2 is a graph showing VT curves based on actually measured values ​​when display is performed in the narrow viewing angle mode and the wide viewing angle mode. Figure 8 It shows that based on Figure 7 The VT curve of the wide viewing angle mode is a graph of the gamma correction table (Table 1) set to γ=2.2. Fig. 9 is a graph showing a gamma correction table for a narrow viewing angle mode and for a wide viewing angle mode. Fig.10 This is a block diagram showing an example of a display method when displaying a viewing angle control pattern. Fig.11 It is a schematic plan view showing an example of one display unit included in a liquid crystal panel. Fig.12 FIG. 1 is a schematic plan view showing an example of a color element when color display is performed by the viewing angle control function. Fig.13 It is a schematic plan view showing an example of a display pattern of a color element. Fig.14 It is a schematic plan view showing another example of a display pattern of a color element. Fig.15 Graphs showing γ curves in the narrow viewing angle mode and the wide viewing angle mode of the liquid crystal display device according to Comparative Example 1. FIG. Fig.16 : is a graph showing a gamma correction table for the narrow viewing angle mode used in Embodiment 1 and a gamma correction table for the narrow viewing angle mode used in Embodiment 2. Fig.17 This is a graph comparing the γ curves when the narrow viewing angle mode and the wide viewing angle mode are observed from the front for Example 1 and Example 2. Fig.18 This is a graph comparing the γ curves when the narrow viewing angle mode and the wide viewing angle mode are observed from the front for Example 2 and Comparative Example 1. Fig.19 This is a graph comparing the γ curves when the narrow viewing angle mode and the wide viewing angle mode are observed from an oblique direction for Example 1 and Example 2. Fig. 20 : is a graph showing a gamma correction table for the narrow viewing angle mode used in Embodiment 4. Fig.21 This is a graph showing the γ curve when the narrow viewing angle mode and the wide viewing angle mode are observed from the front for Example 4. Fig. 22This is a graph showing the γ curve when the narrow viewing angle mode and the wide viewing angle mode are observed from the front for Example 5. DETAILED DESCRIPTION

[0018] Below, the embodiments of the present invention are described. The present invention is not limited to the contents described in the following embodiments, and design changes can be appropriately made within the scope of the composition of the present invention. In addition, in the following description, the same reference numerals are appropriately used in common between different drawings for the same parts or parts with the same functions, and the repeated descriptions are appropriately omitted. The various modes of the present invention can also be appropriately combined within the scope of not departing from the gist of the present invention.

[0019] In this specification, the side closer to the screen (display surface) of the liquid crystal display device is referred to as the "observer side (front side)", and the side farther from the screen (display surface) of the liquid crystal display device is referred to as the "back side". The situation of observing from the normal direction of the front side is also referred to as top view.

[0020] In this specification, "horizontal" means that the tilt angle (including pretilt angle) of the liquid crystal molecules relative to the surface of the first substrate 10 or the second substrate 30 is 0° to 5°, preferably 0° to 3°, and more preferably 0° to 1°. The tilt angle of the liquid crystal molecules refers to the angle at which the long axis of the liquid crystal molecules is tilted relative to the surface of the first substrate 10.

[0021] <Implementation Method 1> The liquid crystal display device involved in the first embodiment includes a liquid crystal panel and a control unit that drives the liquid crystal panel, wherein the liquid crystal panel has a first substrate, a liquid crystal layer, and a second substrate in sequence, the first substrate has a first electrode and a second electrode stacked with a first insulating layer therebetween, or has a first electrode and a second electrode arranged opposite to each other, the second substrate has a third electrode, the control unit has a display mode switching unit, a gamma correction table storage unit, a gamma correction unit, and an image data output unit, the display mode switching unit switches between a narrow viewing angle mode and a wide viewing angle mode by controlling a voltage applied to the third electrode, the gamma correction table storage unit stores a gamma correction table that associates a grayscale value with an applied voltage to the first electrode and / or the second electrode, the gamma correction unit obtains different gamma correction tables from the gamma correction table storage unit in the narrow viewing angle mode and the wide viewing angle mode, performs gamma correction on original image data based on each gamma correction table, and outputs the obtained gamma-corrected image data to the image data output unit, the image data output unit outputs a liquid crystal panel driving signal to the liquid crystal panel to adjust the applied voltage to the first electrode and / or the second electrode.

[0022] Figure 11 is a block diagram showing an example of a display method of a liquid crystal display device according to an embodiment. Figure 1 As shown, the liquid crystal display device 1000 according to the first embodiment includes a liquid crystal panel 100 and a control unit 200 for driving the liquid crystal panel.

[0023] (LCD Panel) Use below Figures 2 to 5 The structure of a liquid crystal panel will be described. Figure 2 1 is a schematic plan view showing an example of a liquid crystal display device according to the first embodiment. Figure 3 yes Figure 2 A schematic top view of a pixel of a liquid crystal display device is shown. Figure 4 It is along Figure 2 A schematic cross-sectional view of line Y1-Y2. Figure 5 It is along Figure 2 A schematic cross-sectional view of line X1-X2.

[0024] like Figure 2 As shown in FIG. 1 , the liquid crystal panel 100 may also be configured with a plurality of pixels arranged in a matrix. The first substrate 10 may have a plurality of gate wirings 1 and a plurality of source wirings 2 arranged to intersect the plurality of gate wirings 1. At the intersection of the gate wirings 1 and the source wirings 2, a thin film transistor 3 (TFT: Thin Film Transistor) may be arranged as a switching element. In this specification, a "pixel" refers to a plurality of pixels. Figure 2 and Figure 3 The region shown is surrounded by two adjacent gate wirings 1 and two adjacent source wirings 2. In this specification, when a first pixel 70 and a second pixel 71 described later are not particularly distinguished, they are simply described as pixels.

[0025] Preferably, each of the plurality of pixels is provided with an optical opening configured to allow light to pass through the liquid crystal panel 100. The optical opening is formed in a Figure 2 The area surrounded by the dotted line inside the pixel shown. When the liquid crystal panel 100 is a transmission type or a semi-transmission type, the optical opening allows the light emitted from the back of the liquid crystal panel 100 to be transmitted toward the front of the liquid crystal panel 100. When the liquid crystal panel 100 is a reflection type or a semi-transmission type, the optical opening transmits the incident light incident from the outside of the liquid crystal panel 100, and the reflected light that is reflected inside the liquid crystal panel 100 and emitted to the outside of the liquid crystal panel 100. In addition, when the optical opening is observed from a top view, for example, it can also overlap with a transmissive component such as a polarizing plate, a color filter, etc. In the first embodiment, the case where the liquid crystal panel 100 is a transmission type is described.

[0026] like Figure 4 and Figure 5 As shown, the liquid crystal panel 100 includes a first substrate 10, a liquid crystal layer 20, and a second substrate 30 in sequence. Figure 4 and Figure 5 In the example, the case where the first substrate 10 has an electrode structure of the FFS (Fringe Field Switching) method having a first electrode 12 and a second electrode 14 stacked via a first insulating layer 13 is illustrated. The case where the first substrate 10 sequentially has a first supporting substrate 11, a first electrode 12, a first insulating layer 13, and a second electrode 14 is illustrated, but it may also sequentially have a first supporting substrate 11, a second electrode 14, a first insulating layer 13, and a first electrode 12.

[0027] In addition, although not shown, the first substrate may also have an IPS (In Plane Switching) electrode structure, which has a first electrode and a second electrode arranged opposite to each other. In the case of the IPS method, the first electrode and the second electrode may also be arranged on the same layer (e.g., the first supporting substrate 11 or the first insulating layer 13).

[0028] The first supporting substrate 11 and the second supporting substrate 31 described later are not particularly limited, and for example, a resin substrate such as polycarbonate, a glass substrate, or the like can be used.

[0029] Examples of the material of the first insulating layer 13 include inorganic materials such as silicon oxide and silicon nitride.

[0030] At least one of the first electrode and the second electrode may include a linear electrode portion that is arranged for each pixel and extends in the first direction. Figure 2 and Figure 3 In FIG. 1 , the case where the second electrode 14 has a linear electrode portion is exemplified.

[0031] The first electrode 12 may be a flat electrode (also referred to as a full-surface electrode) in which no slits or openings are provided in the region at least overlapping the optical opening of the pixel when viewed from above. The first electrode 12 may be configured for each of a plurality of pixels, may be configured for a plurality of pixels in common, or may be formed on the entire display region regardless of the pixel boundary. Examples of the material of the first electrode 12 include transparent conductive materials such as indium tin oxide (ITO) and indium zinc oxide (IZO).

[0032] The second electrode 14 is configured for each pixel. Figure 2 and Figure 3As shown, the second electrode 14 includes a first linear electrode portion 14a extending along the first direction D1. The first linear electrode portion 14a only needs to extend in the first direction D1 in part, and may include a linear electrode portion extending in a direction different from the first direction D1.

[0033] There may be multiple first linear electrode portions 14a. The ends of adjacent first linear electrode portions 14a may be connected by electrode material, and an opening surrounded by the electrode material may be provided. In addition, the second electrode 14 may be a comb-tooth electrode in which the ends of adjacent first linear electrode portions 14a are released, or a slit may be provided between adjacent first linear electrode portions 14a. Figure 2 and Figure 3 In FIG. 1 , the case where the ends of the plurality of first linear electrode portions 14 a are connected by an electrode material and the openings 14 b are provided is exemplified.

[0034] The width of the first linear electrode portion 14a may be, for example, 2 to 5 μm. The width of the slit or opening may be, for example, 2 to 5 μm. The width of the first linear electrode portion 14a and the width of the slit or opening are the widths in a direction perpendicular to the first direction D1.

[0035] Examples of the material of the second electrode 14 include transparent conductive materials such as ITO and IZO. The second electrode 14 may be electrically connected to the corresponding source wiring 2 via a semiconductor layer included in the TFT 3, for example.

[0036] Preferably, either the first electrode 12 or the second electrode 14 is electrically coupled across the plurality of pixels. Crossing the plurality of pixels means being configured to overlap the plurality of pixels across the boundaries of the plurality of pixels. By electrically coupling across the plurality of pixels, a common constant voltage can be applied to either the first electrode 12 or the second electrode 14 for the plurality of pixels.

[0037] The liquid crystal layer 20 contains liquid crystal molecules. The liquid crystal molecules are preferably liquid crystal molecules (positive type) having a positive dielectric anisotropy (Δε) defined by the following formula (L). In addition, the liquid crystal molecules are preferably uniformly oriented in a state where no voltage is applied (no voltage applied state). The direction of the long axis of the liquid crystal molecules in the no voltage applied state is also referred to as the direction of the initial orientation of the liquid crystal molecules. The above-mentioned no voltage applied state also includes the case where a voltage lower than the threshold of the liquid crystal molecules is applied to the liquid crystal layer. Δε = (dielectric constant in the long axis direction of the liquid crystal molecules) - (dielectric constant in the short axis direction of the liquid crystal molecules) (L)

[0038] The second substrate 30 has a third electrode 34. The liquid crystal display device according to the first embodiment switches between a narrow viewing angle mode and a wide viewing angle mode by controlling a voltage applied to the third electrode. Specifically, by applying a driving voltage to the third electrode 34, an electric field is generated in the thickness direction of the liquid crystal layer 20, and the private mode and the public mode can be switched. The display method will be described later.

[0039] like Figure 4 and Figure 5 As shown, the third electrode 34 is arranged on the liquid crystal layer 20 side of the second substrate 30 , and is arranged at a position opposite to the first electrode 12 and / or the second electrode 14 arranged on the liquid crystal layer 20 side of the first substrate 10 via the liquid crystal layer 20 .

[0040] exist Figure 4 and Figure 5 In the example, the second substrate 30 includes the second supporting substrate 31 , the black matrix 33 , the color filter 32 , and the third electrode 34 . However, the color filter 32 and the black matrix 33 may also be formed on the first substrate 10 .

[0041] like Figure 2 and Figure 3 As shown, when the second electrode 14 sets the extension direction of the first linear electrode portion 14a extending in the first direction D1 as the first direction D1, the above-mentioned third electrode 34 may also include a linear electrode portion (second linear electrode portion) 34a extending in a second direction D2 intersecting the first direction D1 when viewed from above.

[0042] The second linear electrode portion 34a may also be arranged between two adjacent pixels in the column direction. The gate wiring 1 may extend in the second direction D2, which is the extending direction of the second linear electrode portion 34a. Figure 2 and Figure 3 As shown in FIG. 1 , the second linear electrode portion 34a may overlap the gate wiring 1 when viewed from above. From the perspective of improving privacy, the width of the second linear electrode portion 34a is preferably wider than the width of the gate wiring 1. Figure 2 and Figure 3 As shown, the second linear electrode portion 34 a may be arranged along the upper and lower ends of one pixel, and a portion of the second linear electrode portion 34 a may overlap with the optical opening.

[0043] The width W of the second linear electrode portion 34 a 34a The width W is preferably 25 μm or more and 35 μm or less, more preferably 27 μm or more and 33 μm or less, and still more preferably 29 μm or more and 31 μm or less. 34a It is the electrode width of the second linear electrode portion 34 a in the direction orthogonal to the second direction D2.

[0044] The third electrode 34 may further include a third linear electrode portion 34b disposed between the plurality of second linear electrode portions 34a. The third linear electrode portion 34b is preferably disposed so as to extend in the second direction D2 when viewed from above and overlap with the optical opening of the pixel. By including the third linear electrode portion 34b in the third electrode 34, the contrast when viewed from an oblique direction can be further suppressed while maintaining a high front contrast. At a position overlapping with the optical opening of the pixel, one third linear electrode portion 34b may be disposed, or a plurality of third linear electrode portions 34b may be disposed.

[0045] The width W of the third linear electrode portion 34 b 34b Preferably, the width is narrower than that of the second linear electrode portion 34a. By providing the third linear electrode portion 34b having a narrower width than that of the second linear electrode portion 34a, the front contrast can be improved in the privacy mode, and the contrast in the oblique direction can be further suppressed.

[0046] The above width W 34b The width W is preferably 2.5 μm or more and 15 μm or less, more preferably 3 μm or more and 13 μm or less, and even more preferably 4 μm or more and 10 μm or less. 34b It is the electrode width of the third linear electrode portion 34 b in the direction orthogonal to the second direction D2.

[0047] When a plurality of third linear electrode portions 34b are arranged, the third linear electrode portions 34b are preferably arranged at equal intervals. A distance d1 between adjacent third linear electrode portions 34b is preferably 3 μm to 20 μm, more preferably 9 μm to 15 μm.

[0048] The second linear electrode portion 34a and the third linear electrode portion 34b are preferably electrically connected to each other. The second linear electrode portion 34a and the third linear electrode portion 34b may be connected by a connection portion at the end of the liquid crystal panel, for example, and the same voltage is preferably applied to the entire third electrode 34.

[0049] The third electrode 34 (the second linear electrode portion 34a and the third linear electrode portion 34b) can also be said to be a horizontal stripe electrode relative to the above-mentioned first direction D1. Since the third electrode 34 is a horizontal stripe electrode, the privacy performance can be improved compared to, for example, the case where it is configured in the same direction as the above-mentioned first direction D1 (the case of a vertical stripe electrode) or the case where it is set to the same shape as the black matrix. Specifically, the front contrast when displayed in the privacy mode can be improved, and the contrast in the inclined direction (for example, in the 0°-180° azimuth, when observed from a polar angle of 35° to 55°) can be reduced. In addition, by setting it as a horizontal stripe, the third electrode 34 can form a portion that does not overlap with the above-mentioned optical opening portion. When displayed in the public mode, the vertical electric field is difficult to act on the opening portion of the image element, so high transmittance and high contrast can be obtained.

[0050] The angle θ1 formed by the first direction D1 and the second direction D2 is preferably greater than 80° and less than 100°, and more preferably greater than 85° and less than 95°. The second direction D2 may also be parallel to the absorption axis 62A of the second polarizing plate 62 or the absorption axis 61A of the first polarizing plate 61. Figure 1 As shown, the second direction D2 is set to be parallel to the absorption axis 62A of the second polarizing plate 62 (0°-180° azimuth).

[0051] The third electrode 34 may be formed of a transparent conductive material. Examples of the transparent conductive material include ITO and IZO.

[0052] like Figure 2 and Figure 3 As shown, the color filter 32 is arranged for each pixel in a manner overlapping with the optical opening when the liquid crystal panel 100 is observed from the front side. The color filter 32 includes, for example, a red color filter 32R, a green color filter 32G, and a blue color filter 32B. For example, the color filter 32 may also continuously form color filters of the same color in the row direction or the column direction of the liquid crystal panel 100. The color filter 32 is preferably a dielectric layer.

[0053] The black matrix 33 is arranged between a plurality of pixels. The black matrix 33 may be arranged between the optical openings adjacent to each other in the row direction or the column direction, or arranged around the optical openings when viewed from above. As the black matrix 33, a black matrix commonly used in the field of liquid crystal display devices can be used, but it is preferably made of resin, and more preferably made of black resin containing a black pigment or dye.

[0054] Although not shown in the figure, an alignment film may be disposed between the first substrate 10 and the liquid crystal layer 20 and between the second substrate 30 and the liquid crystal layer 20. The alignment film controls the initial alignment direction of the liquid crystal molecules in a state where no voltage is applied. The alignment film is preferably a horizontal alignment film. The horizontal alignment film preferably makes the initial pretilt angle of the liquid crystal molecules (in a state where no voltage is applied to the liquid crystal layer) be 0° to 1° relative to the surface of the alignment film.

[0055] In addition, a first polarizing plate 61 and a second polarizing plate 62 may be disposed on the opposite side of the first substrate 10 relative to the liquid crystal layer 20 and on the opposite side of the second substrate 30 relative to the liquid crystal layer 20, respectively. The absorption axis 61A of the first polarizing plate 61 and the absorption axis 62A of the second polarizing plate 62 are preferably disposed so as to be orthogonal to each other as orthogonal Nicol. Figure 1 In the embodiment, the absorption axis 62A of the second polarizing plate 62 is set at an azimuth of 0°-180°, and the absorption axis 61A of the first polarizing plate 61 is set at an azimuth of 90°-270°. The first polarizing plate 61 and the second polarizing plate 62 are preferably linear polarizing plates.

[0056] Although not shown, the liquid crystal panel 100 may also include a dielectric layer between the third electrode 34 and the liquid crystal layer 20. By configuring the dielectric layer, in the common mode, the generation of an unnecessary longitudinal electric field generated between the third electrode 34 and the electrode on the first substrate side can be suppressed. As a result, since the liquid crystal molecules are hardly erected and the lateral electric field driving can be performed, the transmittance and the front contrast ratio of the front white display when displaying in the common mode can be improved.

[0057] The dielectric layer is a layer different from the orientation film, for example, a layer made of a light-transmitting resin. The total light transmittance of the dielectric layer is preferably 80% or more. In this specification, the total light transmittance refers to the total light transmittance measured based on JIS K7361-1. As the dielectric layer, for example, an acrylic resin, a polyimide resin, etc. can be used. The thickness of the dielectric layer is preferably 0.5 μm or more and 4 μm or less.

[0058] The liquid crystal display device according to the first embodiment may also include a backlight source 300 on the back side (first substrate 10 side) of the liquid crystal panel. The backlight source 300 is not particularly limited, and a backlight source 300 commonly used in the field of liquid crystal display devices may be used. The backlight source 300 may be, for example, a side-light type in which a light source is arranged on the end face of a light guide plate, or a direct-light type in which a plurality of light sources are arranged in a plane and a diffusion plate or the like is used to improve uniformity.

[0059] <Display method> like Figure 1As shown, the control unit 200 includes a display mode switching unit 201, a gamma correction table storage unit 202, a gamma correction unit 203, and an image data output unit 204. In addition, the liquid crystal display device 1000 may also include a gate driver 101, a source driver 102, and a third electrode driving circuit 103.

[0060] like Figure 1 As shown, when a display mode switching signal 211 is input from the outside to the display mode switching section 201 of the control section 200, the display mode switching section 201 outputs a display mode signal 212 to the third electrode driving circuit 103 and the gamma correction section 203. First, the following uses Figure 1 and Figure 6 An example of a display method in the narrow viewing angle mode and the wide viewing angle mode will be described. Gamma correction will be described later.

[0061] Figure 6 2 is an explanatory diagram illustrating the structure of the liquid crystal panel and its surroundings. Figure 6 As shown, the gate driver 101 is electrically connected to the gate wiring 1 arranged on the first substrate 10 , the source driver 102 is electrically connected to the source wiring 2 arranged on the first substrate 10 , and the third electrode driving circuit 103 is electrically connected to the third electrode 34 .

[0062] (How to switch the display mode) The display mode switching unit 201 switches between the narrow viewing angle mode and the wide viewing angle mode by controlling the voltage applied to the third electrode 34. In the case of the wide viewing angle mode (public mode), the third electrode driving circuit 103 applies a predetermined AC voltage as a constant voltage to the third electrode 34 based on the display mode signal 212. In the case of the narrow viewing angle mode (privacy mode), the third electrode driving circuit 103 applies a driving voltage having an effective value different from the above-mentioned constant voltage to the third electrode 34 based on the display mode signal 212.

[0063] In this specification, a display mode that displays a first image that can be observed from a narrow viewing angle range including the normal direction of the liquid crystal panel is referred to as a narrow viewing angle mode, and a display mode that can observe the first image from a wide viewing angle range including the narrow viewing angle range is referred to as a wide viewing angle mode. In addition, in this specification, the narrow viewing angle mode is also referred to as a privacy mode, and the wide viewing angle mode is also referred to as a public mode.

[0064] In the above narrow viewing angle range, when the liquid crystal panel is observed at a certain polar angle from an inclined direction (0° azimuth or 180° azimuth), the contrast ratio is preferably 5 or less. The above polar angle is preferably 60° or more, more preferably 45° or more, and further preferably 30° or more, when, for example, the direction perpendicular to the surface of the liquid crystal panel is set to a polar angle of 0° and the direction horizontal to the surface of the liquid crystal panel is set to a polar angle of 90°. The above wide viewing angle range refers to a range of polar angles larger than the polar angles in the above narrow viewing angle range.

[0065] (Public Mode) When black display is set in the common mode, a predetermined AC voltage is applied to the third electrode 34 as a constant voltage, and a liquid crystal panel drive signal 217 is output from the image data output unit 204 to the gate driver 101 and the source driver 102. In addition, black display refers to a display state with the lowest brightness in each display mode, and white display refers to a display state with the highest brightness.

[0066] When the original image signal 213 is input to the original image data generating unit 205, the original image data 214 is output. Without performing gamma correction, the original image data 214 is output to the image data output unit 204, and the image data output unit 204 performs control based on the original image data 214, for example, so that a common voltage shared with the constant voltage is applied to the second electrode 14 and the first electrode 12, and the above-mentioned constant voltage is set to 0V. In addition, the common voltage applied to the second electrode 14 and the first electrode 12 may be the same as the above-mentioned constant voltage, or a voltage less than the threshold value of the liquid crystal molecules may be applied to the above-mentioned constant voltage. This state is also called a no-voltage-applied state.

[0067] In the no voltage applied state, due to Figure 6 In the liquid crystal layer 20 shown, no electric field is generated to drive the liquid crystal molecules, so the liquid crystal molecules are aligned in the initial alignment direction. In the no-voltage application state where no voltage is applied to the liquid crystal layer, the liquid crystal molecules may also be horizontally aligned relative to the first substrate 10. Since the alignment direction of the liquid crystal molecules does not change within the plane of the liquid crystal layer 20, the liquid crystal panel does not transmit light from the back and displays black. The initial alignment direction is preferably parallel to the first substrate 10, and parallel to the absorption axis 61A of the first polarizing plate 61 or the absorption axis 62A of the second polarizing plate 62 when viewed from above.

[0068] When the white display is set in the public mode, for example, in a state where a constant voltage is applied to the third electrode 34, the image data output unit 204 applies a constant voltage (common voltage) to one of the first electrode 12 and the second electrode 14, and applies an AC voltage having an effective value different from the common voltage to the other, outputting the liquid crystal panel drive signal 217. A fringe electric field is formed between the first electrode 12 and the second electrode 14, and on the other hand, unlike the privacy mode described later, the electric field in the thickness direction of the liquid crystal layer 20 is small. Therefore, the liquid crystal molecules change their orientation while being parallel to the first substrate 10 by the electric field formed between the first electrode 12 and the second electrode 14. The liquid crystal molecules rotate in the plane of the liquid crystal layer 20 and change from the initial orientation, so that the long axis direction of the liquid crystal molecules forms an angle with the absorption axis 61A of the first polarizing plate and the absorption axis 62A of the second polarizing plate, and transmit the light from the back of the liquid crystal panel, thereby performing a white display.

[0069] (Privacy Mode) When the black display is set in the privacy mode, the third electrode driving circuit 103 applies a driving voltage having an effective value different from the constant voltage to the third electrode, and the image data output unit 204 controls the application of a constant voltage (common voltage) to the second electrode 14 and the first electrode 12. An oblique electric field is formed between the third electrode 34 and the first electrode 12 and the second electrode 14. The liquid crystal molecules form an angle with respect to the first substrate 10 due to the oblique electric field.

[0070] Since the orientation direction of the liquid crystal molecules does not change within the plane of the liquid crystal layer 20, the liquid crystal panel does not transmit light from the back. On the other hand, the liquid crystal molecules form an angle relative to the first substrate. Therefore, when the liquid crystal panel is observed from a wide viewing angle, a display that is whiter than the black display observed from a narrow viewing angle is observed.

[0071] In the case of setting the white display in the privacy mode, when the third electrode driving circuit 103 applies the driving voltage to the third electrode 34, the image data output unit 204 applies a constant voltage (common voltage) to one of the first electrode 12 and the second electrode 14, and applies an AC voltage having an effective value different from the common voltage to the other electrode for control. The driving voltage applied to the third electrode 34 preferably has an effective value different from the AC voltage applied to the first electrode 12 or the second electrode 14, and more preferably has an effective value greater than the AC voltage applied to the first electrode 12 and the second electrode 14. A fringe electric field is formed between the first electrode 12 and the second electrode 14, and an oblique electric field is formed between the third electrode 34 and the first electrode 12, or between the third electrode 34 and the second electrode 14 with respect to the thickness direction of the liquid crystal layer 20. As a result, since an electric field synthesized by the fringe electric field and the oblique electric field is formed in the liquid crystal layer 20, the liquid crystal molecules form an angle with respect to the first substrate 10 and change the orientation direction by the electric field formed between the first electrode 12, the second electrode 14 and the third electrode 34, thereby performing a white display. Since the liquid crystal molecules form an angle with respect to the first substrate, the first image can be observed from a narrow viewing angle. On the other hand, when the liquid crystal panel is observed from a wide viewing angle, changes in the image such as extremely low contrast can be obtained, making it difficult to observe the first image.

[0072] The white display in the privacy mode and the white display in the public mode can be switched by applying a voltage to the third electrode. Similarly, the black display in the privacy mode and the black display in the public mode can be switched by applying a voltage to the third electrode. The same is true for halftone display.

[0073] In the liquid crystal display device according to the embodiment, as described above, by switching from the wide viewing angle mode (public mode) to the narrow viewing angle mode (privacy mode), high privacy can be obtained when observing from the tilted direction of the liquid crystal panel. In addition, the tilted direction refers to the situation where the right-hand direction of the liquid crystal panel displaying the desired image is set to 0°, and the angle increases in the counterclockwise direction, and the situation is observed from the polar angle of 35° to 55° at the 0° azimuth and the 180° azimuth.

[0074] (Gamma Correction) According to the inventor's research, as described above, when switching between the narrow viewing angle mode and the wide viewing angle mode is performed by controlling the voltage applied to the third electrode on the relative substrate side, the brightness and hue of the liquid crystal panel when observed from the front (normal direction) are sometimes different in the narrow viewing angle mode and the wide viewing angle mode.

[0075] Figure 7 2 is a graph showing VT curves based on measured values ​​when displaying in the narrow viewing angle mode and the wide viewing angle mode. Figure 7As shown, if a constant voltage is applied to the third electrode without gamma correction and the narrow viewing angle mode is set, the VT curve of the narrow viewing angle mode is offset to the high voltage side compared to the VT curve of the wide viewing angle mode. For example, when the applied voltage is about 4.5V, the brightness ratio of the wide viewing angle mode is 1, but it is reduced to about 0.8 in the narrow viewing angle mode. Due to the difference in VT curve characteristics, if the narrow viewing angle mode is driven with the same voltage as the wide viewing angle mode, the brightness is greatly reduced, and the halftone tone is also different. In addition, the reduction in brightness in the narrow viewing angle mode will lead to a reduction in contrast and an increase in power consumption. In embodiment one, by using different gamma correction tables for gamma correction in the narrow viewing angle mode and the wide viewing angle mode, the brightness difference and the color tone difference can be reduced.

[0076] like Figure 1 As shown, when the display mode switching signal 211 is input from the outside to the display mode switching unit 201 of the control unit 200, the display mode switching unit 201 outputs the display mode signal 212 to the gamma correction unit 203. In addition, the original image data generating unit 205 outputs the original image data 214 to the gamma correction unit 203 based on the input original image signal 213.

[0077] The gamma correction unit 203 acquires different gamma correction tables 215 from the gamma correction table storage unit 202 in the narrow viewing angle mode and the wide viewing angle mode according to the input display mode signal 212 .

[0078] The gamma correction table storage unit 202 stores a gamma correction table that associates grayscale values ​​with the applied voltage to the above-mentioned first electrode and / or the above-mentioned second electrode. The above-mentioned gamma correction table can be created, for example, by the following method. First, without performing gamma correction, display is performed in narrow viewing angle mode and wide viewing angle mode, and a VT curve is created based on the measured value. The VT curve is a graph showing the relationship between the applied voltage (V) and the brightness ratio (T). In this specification, the "applied voltage" of the VT curve refers to the voltage applied to the other electrode based on 0V when the electrode of either the first electrode or the second electrode is taken as a common voltage of 0V. In this specification, when the brightness ratio is expressed by 256 grayscales (0 to 255 grayscales), the brightness of 0 grayscale is set to 0, and the brightness of 255 grayscale is set to 1.

[0079] Based on the VT curve measured above, the relationship between the grayscale and the set voltage is calculated in advance to create a gamma correction table so that the grayscale characteristic defined by the grayscale and brightness ratio becomes a specific gamma value. In addition, the curve representing the relationship between the grayscale and the brightness ratio is also called a γ curve. In the first embodiment, the gamma correction table is created separately in the wide viewing angle mode and the narrow viewing angle mode. The set voltage refers to: a voltage set to be output from the image data output unit 204, and is referred to as a voltage applied to the other electrode of the first electrode and the second electrode with 0V as the reference when the electrode of either the first electrode or the second electrode is taken as a common voltage of 0V.

[0080] The relationship among the brightness ratio L, grayscale G, and gamma value γ is expressed by the following equation (1).

[0081] [Mathematical formula 1]

[0082] The gamma correction table storage unit 202 may include a gamma correction table having a constant gamma value between grayscales 0 and 255. The gamma value is preferably 1.8 or more and 2.6 or less, more preferably 2.0 or more and 2.4 or less, and even more preferably 2.2.

[0083] Hereinafter, the gamma correction table used in the narrow viewing angle mode is referred to as the "gamma correction table for narrow viewing angle mode", and the gamma correction table used in the wide viewing angle mode is referred to as the "gamma correction table for wide viewing angle mode". The gamma value of the gamma correction table for narrow viewing angle mode and the gamma value of the gamma correction table for wide viewing angle mode may be the same. The gamma value of the gamma correction table for wide viewing angle mode is preferably greater than or equal to 1.8 and less than or equal to 2.6, more preferably greater than or equal to 2.0 and less than or equal to 2.4, and further preferably 2.2.

[0084] In addition, the gamma value of the gamma correction table for the narrow viewing angle mode may be different from the gamma value of the gamma correction table for the wide viewing angle mode. Preferably, the gamma value of the gamma correction table used in the narrow viewing angle mode is smaller than the gamma value of the gamma correction table used in the wide viewing angle mode. By adopting such a method, the privacy in the narrow viewing angle mode can be further improved.

[0085] The gamma value of the gamma correction table for the wide viewing angle mode is preferably 1.8 or more and 2.6 or less, more preferably 2.0 or more and 2.4 or less, and still more preferably 2.2. The gamma value of the gamma correction table for the narrow viewing angle mode may be smaller than the gamma value of the gamma correction table for the wide viewing angle mode, but from the viewpoint of effectively suppressing the color tone change from the front, the gamma value of the other gamma correction table is preferably 1.8 or more.

[0086] For example, when the gamma value of the wide viewing angle mode gamma correction table is 2.2, the gamma value of the narrow viewing angle mode gamma correction table may also be 2.2. From the perspective of improving privacy in the self-oblique direction, the gamma value of the narrow viewing angle mode gamma correction table may be 2.0 or 1.8.

[0087] Preferably, the difference between the gamma value of the gamma correction table used in the narrow viewing angle mode and the gamma value of the gamma correction table used in the wide viewing angle mode is 0.4 or less. By making the difference in the gamma value 0.4 or less, it is possible to balance the improvement of privacy from the tilt direction and the reduction of the hue from the front. This is because the greater the difference from the gamma value, the greater the privacy from the tilt direction, but when the difference from the gamma value is too large, the difference in hue becomes larger when viewed from the front between the display modes. The difference from the gamma value is more preferably 0.2 or less.

[0088] Figure 8 It shows that based on Figure 7 The VT curve of the wide viewing angle mode is a graph of the gamma correction table (Table 1) set to γ=2.2. Figure 8 The gamma correction table shown is based on Figure 7 The VT curve of the wide viewing angle mode is calculated in advance, and the relationship between the grayscale and the set voltage is calculated so that the grayscale characteristics of the γ curve of the wide viewing angle mode become γ=2.2.

[0089] Fig. 9 is a graph showing a gamma correction table for a narrow viewing angle mode and for a wide viewing angle mode. Fig. 9 The narrow viewing angle mode uses a gamma correction table based on Figure 7 The relationship between the grayscale and the set voltage is calculated in advance so that the grayscale characteristic of the γ curve of the narrow viewing angle mode becomes γ = 2.2. The above-mentioned gamma correction table for the narrow viewing angle mode is also referred to as "Table 2".

[0090] The gamma correction unit 203 performs gamma correction on the original image data based on different gamma correction tables in the narrow viewing angle mode and the wide viewing angle mode, and outputs the obtained gamma-corrected image data 216 to the image data output unit 204. The gamma correction unit 203 refers to the corresponding information between the grayscale and the set voltage in the gamma correction table for the grayscale information of the original image data 214, and outputs the gamma-corrected image data 216 to the image data output unit 204 to obtain the desired brightness ratio. For example, in the wide viewing angle mode, the gamma correction unit 203 uses the gamma correction table to adjust the brightness of the original image data 214. Fig. 9 The wide viewing angle mode uses the gamma correction table (Table 1) for gamma correction. In the narrow viewing angle mode, the Fig. 9 The narrow viewing angle mode is gamma corrected using the gamma correction table (Table 2).

[0091] The image data output unit 204 outputs a liquid crystal panel driving signal 217 to the liquid crystal panel 100 and adjusts a voltage applied to the first electrode and / or the second electrode.

[0092] Taking into account the VT curve characteristics of the liquid crystal panel, different gamma correction tables are used for gamma correction in the narrow viewing angle mode and the wide viewing angle mode. For example, gamma correction is performed in a manner to achieve a grayscale characteristic of γ=2.2 in both the narrow viewing angle mode and the wide viewing angle mode. As a result, the shapes of the γ curves in the narrow viewing angle mode and the wide viewing angle mode become the same, and even if the narrow viewing angle mode and the wide viewing angle mode are switched, the differences in brightness and color tone can be reduced.

[0093] The brightness ratio of the γ curve is a value in which the brightness of 0 grayscale is set to 0 and the brightness of 255 grayscale is set to 1 when the brightness from the front of the liquid crystal panel output along the gamma correction table is represented by 256 grayscales (0 to 255 grayscales).

[0094] (Implementation Method 2) In the second embodiment, the gamma correction table storage unit includes a gamma correction table having a plurality of gamma values ​​between grayscales 0 to 255.

[0095] In the second embodiment, at least one of the gamma correction table for narrow viewing angle mode and the gamma correction table for wide viewing angle mode only needs to have a plurality of gamma values ​​between grayscales 0 to 255. One of the gamma correction table for narrow viewing angle mode and the gamma correction table for wide viewing angle mode may have a constant gamma value between grayscales 0 to 255, and the other may have a plurality of gamma values ​​between grayscales 0 to 255. By adopting such a method, the change in the brightness ratio of the halftone in the narrow viewing angle mode can be made smaller than the change in the brightness ratio of the halftone in the wide viewing angle mode, and the brightness change from the front can be further suppressed.

[0096] Preferably, the gamma value of the gamma correction table used in the wide viewing angle mode is constant between grayscales 0 and 255, and the gamma value of the gamma correction table used in the narrow viewing angle mode has multiple values ​​between grayscales 0 and 255.

[0097] If any grayscale from 0 to 255 is set to X, then: in grayscales greater than 0 and less than X, the gamma value of the gamma correction table used in the narrow viewing angle mode is smaller than the gamma value of the gamma correction table used in the wide viewing angle mode, and in grayscales greater than X and less than 255, the gamma value of the gamma correction table used in the narrow viewing angle mode is greater than the gamma value of the gamma correction table used in the wide viewing angle mode.

[0098] For example, when the gamma value of the gamma correction table for wide viewing angle mode is 2.2 (constant) in the grayscale of 0 to 255, the gamma value of the gamma correction table for narrow viewing angle mode may be less than 2.2 in the grayscale of 0 or more and less than X, and may exceed 2.2 in the grayscale of X or more and less than 255. The gamma value in the grayscale of 0 or more and less than X in the gamma correction table for narrow viewing angle mode is preferably less than 2.0, and is preferably greater than 1.8 from the viewpoint of taking into account both the visual recognizability of the narrow viewing angle mode and suppressing the change of the color tone from the front. The gamma value in the grayscale of X or more and less than 255 in the gamma correction table for narrow viewing angle mode is preferably greater than 2.4, and is preferably less than 2.6 from the viewpoint of taking into account both the visual recognizability of the narrow viewing angle mode and suppressing the change of the color tone from the front. The above-mentioned arbitrary grayscale X can be any one of 64, 128, and 192. There is a trade-off relationship between the viewing angle control (veil-view) performance and the effect of suppressing the color tone change from the front side in the narrow viewing angle mode and the wide viewing angle mode.

[0099] If any grayscale between 0 and 255 is set to X, and any grayscale greater than X is set to Y, then: in grayscales greater than 0 and less than X, the gamma value of the gamma correction table used in the narrow viewing angle mode is smaller than the gamma value of the gamma correction table used in the wide viewing angle mode, and in grayscales greater than Y and less than 255, the gamma value of the gamma correction table used in the narrow viewing angle mode is greater than the gamma value of the gamma correction table used in the wide viewing angle mode.

[0100] For example, when the gamma value of the gamma correction table for wide viewing angle mode is 2.2 (constant) in the grayscale of 0 to 255, the gamma value of the gamma correction table for narrow viewing angle mode may be less than 2.2 in the grayscale of 0 or more and less than X, and may exceed 2.2 in the grayscale of Y or more and less than 255. The gamma value in the grayscale of 0 or more and less than X in the gamma correction table for narrow viewing angle mode is preferably 2.0 or less, and from the viewpoint of taking into account both the visual recognizability of the narrow viewing angle mode and suppressing the change of the color tone from the front, it is preferably 1.8 or more. The gamma value in the grayscale of Y or more and less than 255 in the gamma correction table for narrow viewing angle mode is preferably 2.4 or more, and from the viewpoint of taking into account both the visual recognizability of the narrow viewing angle mode and suppressing the change of the color tone from the front, it is preferably 2.6 or less.

[0101] The above arbitrary grayscales X and Y may be any one of 64, 128, and 192. For example, the specific combination of X and Y may be X=64, Y=192, X=64, Y=128, or X=128, Y=192. Between grayscales X and Y, the gamma value may be appropriately set for each grayscale so that the brightness ratio increases smoothly from grayscale X to grayscale Y.

[0102] (Implementation Method 3) In the third embodiment, based on the switching of the display mode of the normal display of the first image, the privacy can be further improved by combining it with the viewing angle control function of overlapping the second image on the first image. Fig.10 An example of a method of displaying an image using the viewing angle control function will be described. Fig.10 2 is a block diagram showing an example of a display method when displaying a viewing angle control pattern. The control unit 200 inputs different image signals to the first and second pixels so that a second image different from the first image can be observed from a wide viewing angle. This display method is also called a viewing angle control function.

[0103] like Fig.10 As shown, the control unit 200 may further include a viewing angle control pattern database 206 (hereinafter referred to as database 206 ) storing information related to viewing angle control patterns (viewing angle control pattern data) and a viewing angle control switching unit 207 .

[0104] When the viewing angle control display switching signal 218 is input to the viewing angle control switching unit 207, the viewing angle control switching unit 207 obtains the viewing angle control pattern data 219 from the database 206, and outputs the viewing angle control pattern image signal 220 to the image data output unit 204. The image data output unit 204 synthesizes the gamma-corrected image data 216 output from the gamma correction unit 203 and the viewing angle control pattern image signal 220, and outputs the liquid crystal panel driving signal 217 to the gate driver 101 and the source driver 102.

[0105] The display based on the viewing angle control function can further improve privacy by combining it with the narrow viewing angle mode. Therefore, when the narrow viewing angle mode is selected, the viewing angle control display switching signal 218 can be input from the above-mentioned display mode switching unit 201 to the viewing angle control switching unit 207.

[0106] For example, when a common voltage is applied to the second electrode 14, different voltages are applied to the first electrodes 12 corresponding to the first pixel 70 and the second pixel 71, respectively, so that the second image is observed from a wide viewing angle. In this case, the first electrode 12 is preferably provided for each pixel. On the other hand, when a common voltage is applied to the first electrode 12, different voltages are applied to the second electrodes 14 corresponding to the first pixel 70 and the second pixel 71, respectively, so that the second image is observed from a wide viewing angle.

[0107] Fig.11 It is a schematic plan view showing an example of one display unit included in a liquid crystal panel. Fig.12FIG. 1 is a schematic top view showing an example of a color element when a color display is performed using a viewing angle control function. Fig.11 As shown, the liquid crystal panel 100 may have a plurality of display units 72 for displaying images using a viewing angle control function. Preferably, the display units 72 are arranged adjacent to each other in a column direction and include a pair of pixels consisting of a first pixel 70 selected from an odd row and a second pixel 71 selected from an even row.

[0108] like Figure 2 and Fig.11 As shown, the first pixel 70 and the second pixel 71 can be captured as one pixel respectively. Fig.12 As shown, a combination of a first red pixel 70R, a first green pixel 70G, and a first blue pixel 70B is captured as a first pixel 70, and a combination of a second red pixel 71R, or a second green pixel 71G, and a second blue pixel 71B is captured as a second pixel 71. In addition, when color display is performed using a normal display method, color display can be performed by independently driving each pixel including red, green, and blue. In the case of normal color display, display can be performed at a resolution twice that of color display using a viewing angle control function.

[0109] In the case of color display, preferably, the liquid crystal panel includes: a red display unit 72R including a first red pixel 70R and a second red pixel 71R, a green display unit 72G including a first green pixel 70G and a second green pixel 71G, and a blue display unit 72B including a first blue pixel 70B and a second blue pixel 71B. The color element 73 may include a red display unit 72R, a green display unit 72G, and a blue display unit 72B. The first and second pixels of each color overlap with the color filter 32R of each color at the optical opening portion, respectively.

[0110] As a method of displaying an image using the viewing angle control function, for example, if the data value of the brightness of the original image to be displayed as the first image is set to Data1, Data1 is divided into two data values ​​Data2 and Data3 that are equal to each other, and the data value of Data1+Data2 is input to either the first pixel 70 or the second pixel 71, and the data value of Data1-Data3 is input to the other. When the liquid crystal panel is observed from a narrow viewing angle, the brightness of the first pixel 70 and the brightness of the second pixel 71 are spatially averaged and visually recognized as the brightness of the original image. On the other hand, when observed from a wide viewing angle, it is visually recognized as the brightness of Data1+Data2 or the brightness of Data1-Data3.

[0111] Fig.13is a schematic top view showing an example of a display pattern of a color element. Fig.13 As shown, when the first red pixel 70R, the second green pixel 71G, and the second blue pixel 71B are set to black display, and the second red pixel 71R, the first green pixel 70G, and the first blue pixel 70B are set to white display, when observed from the 225° azimuth, the liquid crystal molecules present in the second red pixel 71R are observed in the short axis direction of the liquid crystal molecules with high delay, so red is observed, but since the liquid crystal molecules present in the first green pixel 70G and the first blue pixel 70B are observed in the long axis direction of the liquid crystal molecules with low delay, the corresponding color is not observed. As a result, it is visually recognized as red. On the other hand, if observed from the 315° azimuth, the liquid crystal molecules present in the first green pixel 70G and the first blue pixel 70B are observed in the short axis direction of the liquid crystal molecules, so the mixed color of blue and green, that is, cyan, can be visually recognized, but since the liquid crystal molecules present in the second red pixel 71R are observed in the long axis direction, the corresponding color is not observed. As a result, it is visually recognized as cyan.

[0112] Fig.14 FIG. 1 is a schematic top view showing another example of a display pattern of a color element. Fig.14 As shown, when the first red pixel 70R, the first green pixel 70G and the second blue pixel 71B are set to black display and the second red pixel 71R, the second green pixel 71G and the first blue pixel 70B are set to white display, when observed from a 225° azimuth, it is visually identified as a mixture of red and green, that is, yellow, and when observed from a 315° azimuth, it is visually identified as blue.

[0113] By combination Fig.13 The display pattern of the color element shown and Fig.14 The display pattern of the color element shown is observed as a white display when viewed from the normal direction (front) of the liquid crystal panel. In the halftone range, the difference in contrast between the images visually recognized by the plurality of pixels arranged on the odd-numbered row side and the plurality of pixels arranged on the even-numbered row side is large. It is preferable to create a soft viewing angle control pattern in such a halftone range that can sufficiently obtain the difference in visual recognition between the odd-numbered row side and the even-numbered row side.

[0114] The second image is preferably a viewing angle control pattern. The viewing angle control pattern is a display image that is displayed on the first image and is difficult to visually identify the first image. By displaying the viewing angle control pattern, privacy can be further improved. The viewing angle control pattern is not particularly limited, and can display geometric patterns such as stripes and checkered patterns, text, images, etc. [Example]

[0115] Hereinafter, the effects of the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[0116] (Example 1) Example 1 is a specific example of implementation mode 1, having Figure 1 to Figure 6 The first substrate 10 has an FFS type electrode structure, and the first electrode 12 is a full-surface electrode without an opening. The second electrode 14 is configured as follows: for each pixel configuration, there are three first linear electrode portions 14a with a width of 2.5 μm, and there are openings 14b with a width of 3.5 μm between the first linear electrode portions 14a. The liquid crystal molecules are set to positive liquid crystal materials.

[0117] The third electrode 34 is disposed on the second substrate 30. The third electrode 34 includes a second linear electrode portion 34a disposed along the upper and lower ends of the pixel and two third linear electrode portions 34b overlapping the optical aperture. The width W of the second linear electrode portion 34a is 34a is 31 μm, and the width W of the third linear electrode portion 34 b is 34b The distance d1 between adjacent third linear electrode portions 34 b is 11 μm.

[0118] An angle θ1 formed by the extending direction (first direction D1) of the first linear electrode portion 14a and the extending directions (second direction D2) of the second linear electrode portion 34a and the third linear electrode portion 34b of the third electrode is 80°.

[0119] In the wide viewing angle mode, a constant voltage (common voltage) is applied to the third electrode. As the constant voltage, a fixed voltage of 0V is applied. In the narrow viewing angle mode, an AC voltage of 4V is applied to the third electrode relative to the constant voltage. In the wide viewing angle mode and the narrow viewing angle mode, grayscale display is performed by applying a common voltage (0V) to the first electrode 12 and changing the voltage applied to the second electrode 14.

[0120] Above Figure 7 to Figure 9 This is also a graph of Example 1. In Example 1, based on Figure 7 The VT curves for narrow and wide viewing angle modes are shown, creating Fig. 9 The gamma correction table for the wide viewing angle mode in which the grayscale characteristic is set to γ=2.2 and the gamma correction table for the narrow viewing angle mode in which the grayscale characteristic is set to γ=2.2 are shown. Fig. 9 The wide viewing angle mode uses a gamma correction table with Figure 8 The gamma correction table for the wide viewing angle mode is the same as that for the wide viewing angle mode. In Embodiment 1, gamma correction is performed using Table 1 in the wide viewing angle mode, and gamma correction is performed using Table 2 in the narrow viewing angle mode.

[0121] In Example 1, the grayscale characteristics of the wide viewing angle mode and the narrow viewing angle mode after gamma correction are corrected to γ=2.2, so the γ curves of the wide viewing angle mode and the narrow viewing angle mode are consistent. Therefore, even if the wide viewing angle mode and the narrow viewing angle mode are switched, the brightness and color tone of the liquid crystal panel will not change.

[0122] (Comparative Example 1) In Comparative Example 1, the same liquid crystal panel as in Example 1 was used, and gamma correction was performed using the same gamma correction table in both the narrow viewing angle mode and the wide viewing angle mode. Figure 8 The gamma correction table shown in Table 1 performs gamma correction.

[0123] Fig.15 Graphs showing γ curves in the narrow viewing angle mode and the wide viewing angle mode of the liquid crystal display device according to Comparative Example 1. Fig.15 As shown in the figure, when the same gamma correction table is used for gamma correction in narrow viewing angle mode and wide viewing angle mode, the shape of the gamma curve in wide viewing angle mode is very different from that in narrow viewing angle mode. Compared with wide viewing angle mode, the brightness of narrow viewing angle mode is high on the low grayscale side and low on the high grayscale side. When displayed in narrow viewing angle mode, the color tone is not clear.

[0124] (Example 2) In Example 2, the same liquid crystal panel as in Example 1 was used, and gamma correction was performed in the wide viewing angle mode using Table 1 in the same manner as in Example 1. Figure 7 For the VT curve of the narrow viewing angle mode shown, a gamma correction table for the narrow viewing angle mode was created (Table 3) in which the grayscale characteristic was set to γ=1.8, and gamma correction was performed. Fig.16 : is a graph showing a gamma correction table for the narrow viewing angle mode used in Embodiment 1 and a gamma correction table for the narrow viewing angle mode used in Embodiment 2.

[0125] Fig.17 This is a graph comparing the γ curves when the narrow viewing angle mode and the wide viewing angle mode are observed from the front for Example 1 and Example 2. Fig.18 2 is a graph comparing the γ curves when the narrow viewing angle mode and the wide viewing angle mode are observed from the front for Example 2 and Comparative Example 1. Fig.17 As shown in FIG. 1 , the brightness ratio of Example 2 is slightly higher than that of Example 1 in the halftone mode of the narrow viewing angle mode, but Fig.18 As shown, compared with Comparative Example 1, the difference in brightness ratio between the narrow viewing angle mode and the wide viewing angle mode is small, and the sense of incongruity in color tone is reduced.

[0126] Fig.192 is a graph comparing the γ curves when the narrow viewing angle mode and the wide viewing angle mode are observed from an oblique direction for Example 1 and Example 2. Fig.19 As shown, when observed from an oblique direction (180° azimuth, polar angle 45°), it is confirmed that: in both Examples 1 and 2, the brightness ratio of the narrow viewing angle mode is higher than that of the wide viewing angle mode at grayscale 0, and privacy is obtained by limiting visual recognition. In addition, in Example 2, the brightness ratio of the narrow viewing angle mode in halftone is higher than that of Example 1, and when observed from an oblique direction, the visual recognition becomes lower and looks whitish, so the privacy can be further improved.

[0127] (Example 3) In Example 3, the same liquid crystal panel as in Example 1 was used, and gamma correction was performed in the wide viewing angle mode using Table 1 in the same manner as in Example 1. Figure 7 For the VT curve of the narrow viewing angle mode shown, a gamma correction table for the narrow viewing angle mode was created (Table 4) in which the grayscale characteristic was set to γ=2.0, and gamma correction was performed.

[0128] In Example 3, the difference in brightness ratio between the narrow viewing angle mode and the wide viewing angle mode is also smaller than in Comparative Example 1, and the inharmonious feeling of the color tone is reduced. In addition, in Example 3, the brightness ratio of the halftone in the narrow viewing angle mode is higher than that in Example 1, and the visual recognition is reduced when observed from an oblique direction. Although it is worse than Example 2, the privacy can be improved compared with Example 1.

[0129] (Example 4) Example 4 is a specific example of implementation mode 2, and a gamma correction table having multiple gamma values ​​between grayscale 0 to 255 is used. In Example 4, the same liquid crystal panel as in Example 1 is used, and in the wide viewing angle mode, gamma correction is performed using Table 1 in which the gamma value is 2.2 and constant between grayscale 0 to 255. In the narrow viewing angle mode of Example 4, as shown in Table 1 below, a gamma correction table (Table 5) is created in which the gamma value varies between grayscale 0 to 255 by 2.0 to 2.4, and gamma correction is performed. Fig. 20 : is a graph showing a gamma correction table for the narrow viewing angle mode used in Embodiment 4.

[0130] As described above, the liquid crystal panel 100 increases the brightness of the oblique black display (0 grayscale) in the narrow viewing angle mode, so that the contrast of the band observed from the oblique direction is extremely reduced, thereby reducing visual recognition and improving privacy. In Example 4, in the narrow viewing angle mode, γ is set to be non-fixed and varies in each grayscale. When it is below 64 grayscales, γ=1.8, and when it is above 192 grayscales, γ=2.6. In Example 4, by changing the γ value from 1.8 to 2.6 in the range of 64 to 192 grayscales, the contrast limited to halftones can be reduced compared to Example 1. Usually, images in display are mostly expressed in halftones, so by reducing the contrast of halftones, the visual recognition when observed from an oblique direction in the narrow viewing angle mode can be further reduced, and privacy can be improved.

[0131] Fig.21 4 is a graph showing the γ curve when the narrow viewing angle mode and the wide viewing angle mode are observed from the front. Fig.21 As shown in the figure, the change in the brightness ratio between 64 and 192 grayscales is smaller in the narrow viewing angle mode than in the wide viewing angle mode. Since the γ value is suppressed to change within the range of 1.8 to 2.6, the front visibility in the narrow viewing angle mode is at a level where the change in brightness cannot be visually recognized, which is good.

[0132] (Examples 5 to 7) In the narrow viewing angle mode, Examples 5 to 7 are the same as Example 4 except that gamma correction tables (Tables 6 to 8) are created to vary the γ value between grayscales 0 to 255 and gamma correction is performed as shown in Table 1 below.

[0133] [Table 1]

[0134] In Example 5, by changing the γ value from 2.0 to 2.4 within the range of 64 to 192 grayscales, the contrast only in halftones can be reduced compared to Example 1. As a result, in the narrow viewing angle mode, when viewed from an oblique direction, visibility can be further reduced, thereby improving privacy. Fig. 22 2 is a graph showing the γ curve when the narrow viewing angle mode and the wide viewing angle mode are observed from the front for Example 5. Fig. 22 As shown, in Example 5, the change in the brightness ratio between 64 and 192 grayscales is smaller in the narrow viewing angle mode than in the wide viewing angle mode, and the front visibility in the narrow viewing angle mode is at a level where the brightness change cannot be visually recognized, which is good.

[0135] In Examples 6 and 7, the changes in the brightness ratio between 64 to 128 grayscales and 128 to 192 grayscales are smaller in the narrow viewing angle mode than in the wide viewing angle mode, and the front visual recognition in the narrow viewing angle mode is good. In addition, compared with Example 1, Examples 6 and 7 can reduce the contrast between 64 to 128 grayscales and 128 to 192 grayscales, respectively.

[0136] In the narrow viewing angle mode of Examples 1 to 7 and Comparative Example 1, (1) visibility in an oblique direction, (2) brightness from the front, and (3) color tone from the front were evaluated based on the following criteria. The results are summarized in Table 2 below.

[0137] (1) Visual recognizability from the oblique direction The liquid crystal display devices of the embodiments and comparative examples are used to display the display image in a narrow viewing angle mode, and are observed from an inclined direction (0-180° azimuth, polar angle 45°) to evaluate whether the display image can be visually recognized by eye. The visibility of the display image in the narrow viewing angle mode of Comparative Example 1 is set to 1 point, and the visual recognition in the narrow viewing angle mode of each embodiment is scored with 1 to 3 points. It can be said that the higher the score, the more difficult it is to visually recognize the display image in the narrow viewing angle mode, and the higher the privacy. As the above-mentioned display image, a colorful landscape painting is displayed.

[0138] (2) Brightness of the front For the liquid crystal display devices of the embodiment and the comparative example, the luminance from the normal direction in the wide viewing angle mode at 255 grayscales was set to 100%, and the luminance from the normal direction in the narrow viewing angle mode at 255 grayscales was measured. If the front luminance in the narrow viewing angle mode was 90% or more, it was set to 0, and if it was less than 90%, it was set to ×.

[0139] (3) Positive color tone The liquid crystal display devices of the embodiment and the comparative example were observed from the normal direction and displayed with a display image, and when the wide viewing angle mode and the narrow viewing angle mode were switched, five panelists were asked to judge whether the color tone of the narrow viewing angle mode was inconsistent with that of the wide viewing angle mode based on the following criteria. As the display image, a color landscape painting was displayed. 0: 4 or 5 out of 5 people do not notice any difference in color tone between wide viewing angle mode and narrow viewing angle mode △: 2 or 3 out of 5 people did not notice the difference in color tone between wide viewing angle mode and narrow viewing angle mode ×: 0 or 1 out of 5 people did not notice a difference in color tone between the wide viewing angle mode and the narrow viewing angle mode

[0140] [Table 2] Description of Reference Numerals

[0141] 1: Gate wiring 2: Source wiring 3: Thin Film Transistor 10: First substrate 11: First supporting substrate 12: First electrode 13: First insulation layer 14: Second electrode 14a: First linear electrode portion 14b: Opening 20: Liquid crystal layer 30: Second substrate 31: Second supporting substrate 32, 32B, 32G, 32R: Color filters 33: Black Matrix 34: The third electrode 34a: Second linear electrode portion 34b: Third linear electrode portion 61: First polarizing plate 61A, 62A: Absorption axis 62: Second polarizing plate 70: First Pixel 70B: First blue pixel 70G: The first green pixel 70R: First red pixel 71: Second Pixel 71B: Second blue pixel 71G: Second green pixel 71R: Second red pixel 72, 72B, 72G, 72R: Display units 73: Color components 100: LCD panel 101: Gate Driver 102: Source Driver 103: Third electrode driving circuit 200: Control Department 201: Display mode switching unit 202: Gamma correction table storage unit 203: Gamma Correction Department 204: Image data output unit 205: Original image data generation unit 206: Viewing angle control pattern database 207: View control switching unit 211: Display mode switching signal 212: Display mode signal 213: Original image signal 214: Original image data 215: Gamma Correction Table 216: Image data after gamma correction 217: LCD panel drive signal 218: Viewing angle control display switching signal 219: Viewing angle control pattern data 220: Viewing angle control pattern image signal 300: Backlight 1000: Liquid crystal display device

Claims

1. A liquid crystal display device, characterized in that: The invention comprises a liquid crystal panel and a control unit for driving the liquid crystal panel. The liquid crystal panel comprises a first substrate, a liquid crystal layer and a second substrate in sequence. The first substrate has a first electrode and a second electrode stacked with a first insulating layer interposed therebetween, or has a first electrode and a second electrode arranged opposite to each other, The second substrate has a third electrode, The control unit includes a display mode switching unit, a gamma correction table storage unit, a gamma correction unit, and an image data output unit. The display mode switching unit switches between the narrow viewing angle mode and the wide viewing angle mode by controlling the voltage applied to the third electrode. The gamma correction table storage unit stores a gamma correction table that associates grayscale values ​​with voltages applied to the first electrode and / or the second electrode. The gamma correction unit obtains different gamma correction tables from the gamma correction table storage unit in the narrow viewing angle mode and the wide viewing angle mode, performs gamma correction on the original image data based on each gamma correction table, and outputs the obtained gamma-corrected image data to the image data output unit. The image data output unit outputs a liquid crystal panel driving signal to the liquid crystal panel, and adjusts a voltage applied to the first electrode and / or the second electrode.

2. The liquid crystal display device according to claim 1, wherein A difference between a gamma value of the gamma correction table used in the narrow viewing angle mode and a gamma value of the gamma correction table used in the wide viewing angle mode is 0.4 or less.

3. The liquid crystal display device according to claim 1, wherein A gamma value of the gamma correction table used in the narrow viewing angle mode is smaller than a gamma value of the gamma correction table used in the wide viewing angle mode.

4. The liquid crystal display device according to claim 1, wherein The gamma correction table storage unit includes a gamma correction table having a constant gamma value between gray levels 0 to 255.

5. The liquid crystal display device according to claim 1, wherein: The gamma correction table storage unit includes a gamma correction table having a plurality of gamma values ​​between grayscales 0 to 255.

6. The liquid crystal display device according to claim 4 or 5, characterized in that: The gamma value of the gamma correction table used in the wide viewing angle mode is constant between grayscales 0 and 255, and the gamma value of the gamma correction table used in the narrow viewing angle mode has a plurality of values ​​between grayscales 0 and 255.

7. The liquid crystal display device according to claim 6, wherein: When any grayscale between 0 and 255 is set as X, In grayscales greater than or equal to 0 and less than X, the gamma value of the gamma correction table used in the narrow viewing angle mode is smaller than the gamma value of the gamma correction table used in the wide viewing angle mode, In grayscales greater than or equal to X and less than or equal to 255, a gamma value of the gamma correction table used in the narrow viewing angle mode is greater than a gamma value of the gamma correction table used in the wide viewing angle mode.

8. The liquid crystal display device according to claim 6, wherein: When any grayscale between 0 and 255 is set as X, and any grayscale greater than X is set as Y, In grayscales greater than or equal to 0 and less than X, the gamma value of the gamma correction table used in the narrow viewing angle mode is smaller than the gamma value of the gamma correction table used in the wide viewing angle mode, In grayscales greater than or equal to Y and less than or equal to 255, a gamma value of the gamma correction table used in the narrow viewing angle mode is greater than a gamma value of the gamma correction table used in the wide viewing angle mode.

9. The liquid crystal display device according to claim 1, wherein: At least one of the first electrode and the second electrode includes a linear electrode portion that is arranged for each pixel and extends in a first direction. The third electrode includes a linear electrode portion extending in a second direction intersecting the first direction in a plan view.

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