JP6346788B2 - Liquid crystal display device and control method thereof - Google Patents

Description

  The present invention relates to a liquid crystal display device and a control method thereof.

  2. Description of the Related Art Conventionally, as a display format of a liquid crystal display device, a horizontal electric field method is known in which display is performed by rotating the molecular axis direction (director) of liquid crystal molecules in a plane parallel to a substrate. For example, Patent Document 1 discloses an IPS (In-Plane Switching) mode liquid crystal display device, which is a representative example of a horizontal electric field method.

  By the way, in general, in the liquid crystal display device, since the alignment state of the liquid crystal molecules relatively changes according to the viewing angle direction, the viewing angle dependency of the display quality is high, and the viewing angle at which good display characteristics can be obtained is narrow. Has drawbacks.

  On the other hand, the liquid crystal display device of the horizontal electric field type has a viewing angle dependency because only the minor axis direction of the liquid crystal molecules is basically observed even when the viewer views the display screen from different viewing angle directions. It is small and has a characteristic that good display characteristics can be obtained over a wide viewing angle range. Therefore, in recent years, horizontal electric field type liquid crystal display devices tend to be frequently used.

  Conventionally, as a technique for improving the viewing angle dependency of a liquid crystal display device, a display pattern that combines a low gradation and a high gradation that hardly affect the viewing angle when displaying an intermediate gradation image. A technique for performing viewing angle improvement processing for reproducing the image is known.

  FIG. 20 is an explanatory diagram showing a method of viewing angle improvement processing. As shown in this figure, in the viewing angle improvement processing, an input image of intermediate gradation (see FIG. 20A) is a staggered pattern in which low gradation pixels and high gradation pixels are alternately arranged (see FIG. 20). By expressing it with a display pattern such as 20 (see (b)), it is possible to suppress problems such as whitening that occur when viewed from an oblique direction.

Japanese Patent Application Laid-Open No. 07-036058 (published on February 7, 1995)

  However, when the above-described viewing angle improvement processing is performed in the horizontal electric field type liquid crystal display device, as shown in FIG. 21, the display quality called shadow (color misregistration) deteriorates in a region other than the target region of the viewing angle improvement processing. It will occur.

  That is, in the case of a horizontal electric field type liquid crystal display device, the pixel electrode (pixel electrode) and the counter electrode are arranged so as to be adjacent to each other with an insulating layer interposed therebetween, so that capacitive coupling is established between the pixel electrode and the counter electrode. It is easy for crosstalk to occur. Also, when crosstalk occurs between the pixel electrode and the counter electrode, the potential of the counter electrode fluctuates due to the influence of the potential change of the pixel electrode, and the potential difference between the counter electrode and the pixel electrode becomes The potential difference corresponding to the image data to be displayed deviates and shadows occur. For this reason, when the viewing angle improvement process is performed on a part of the display area in the horizontal electric field type liquid crystal display device, a shadow is generated in an area other than the target area of the viewing angle improvement process.

  It should be noted that the shadow caused by such crosstalk displays a predetermined display pattern such as a staggered pattern in a liquid crystal display device that performs polarity inversion driving that inverts the polarity of the potential applied to the pixel electrode at predetermined intervals. This is especially likely to occur.

  The present invention has been made in view of the above-described problems, and the object of the present invention is to cause a shadow due to crosstalk between a picture element electrode and a counter electrode during a viewing angle improvement process in a liquid crystal display device. It is to suppress this.

  A liquid crystal display device according to one embodiment of the present invention is provided at each intersection of a plurality of gate bus lines, a plurality of source bus lines intersecting with the gate bus lines, and the gate bus lines and the source bus lines. A liquid crystal display device having a liquid crystal panel having a predetermined picture element, wherein an intermediate-tone image is converted from an input image data to a picture element having a gradation lower than the gradation and a gradation higher than the gradation. A viewing angle improvement processing unit for performing a viewing angle improvement process for converting the image into a reproducible image by a display pattern combined with a picture element, and an intensity parameter selection unit for setting an intensity parameter of the viewing angle improvement process. The intensity parameter selection unit is configured to display a gate bus line when the display area for performing the viewing angle improvement process is only a part of the extending direction of the gate bus line on the display screen of the liquid crystal panel. The intensity parameter is set to be smaller than that in the entire stretching direction, and the viewing angle improvement processing unit increases the gradation between the low gradation picture element and the high gradation picture element as the intensity parameter increases. It is characterized by setting a large value difference.

  According to the above configuration, when the display area for performing the viewing angle improvement processing is only a part of the extending direction of the gate bus line on the display screen of the liquid crystal panel, the low gradation picture element and the high gradation picture element By setting the difference in the gradation values to be small, it is possible to reduce the bias of the polarity of the applied voltage with respect to the pixels arranged in the extending direction of the gate bus line. Thereby, it is possible to obtain the effect of improving the viewing angle while suppressing the occurrence of shadow by reducing the crosstalk generated between the picture element electrode and the counter electrode during the viewing angle improving process. In addition, when the display area where the viewing angle improvement process is performed extends over the entire extension direction of the gate bus line, the difference in the gradation value between the low gradation picture element and the high gradation picture element is set to be larger. A large viewing angle improvement effect can be obtained.

(A) is explanatory drawing which shows schematic structure of the liquid crystal display device concerning one Embodiment of this invention, (b) is sectional drawing of the AA cross section shown to (a). It is explanatory drawing which shows the structure of the liquid crystal panel with which the liquid crystal display device shown in FIG. 1 is equipped. It is a top view of the sub pixel in the liquid crystal panel of FIG. It is sectional drawing of the sub pixel in the liquid crystal panel of FIG. FIG. 3 is an explanatory diagram schematically showing a voltage applied between a pixel electrode and a counter electrode and an alignment state of liquid crystal molecules in the liquid crystal panel of FIG. 2, (a) is a state when no voltage is applied; (B) has shown the state at the time of voltage application. FIG. 4 is a plan view showing in more detail the configuration of the subpixel shown in FIG. 3. FIG. 7 is an equivalent circuit diagram of the subpixel shown in FIG. 6. FIG. 7 is an explanatory diagram illustrating a relationship between an insulating film between a pixel electrode and a counter electrode and a thickness of a liquid crystal layer in the sub-pixel illustrated in FIG. 6. It is explanatory drawing which shows the ripple noise produced by the crosstalk of a pixel electrode and a counter electrode. (A) is explanatory drawing which shows the electric current which flows into a pixel electrode by the crosstalk of a pixel electrode and a counter electrode, when a switching element becomes conductive, (b) shows the mode in case a switching element is a interruption | blocking state. It is explanatory drawing. It is explanatory drawing which shows an example of the image superimposed by the superimposition process part with which the liquid crystal display device shown in FIG. 1 is equipped. (A)-(f) is explanatory drawing which shows the viewing angle improvement process according to the setting method and intensity | strength parameter of the intensity | strength parameter in the liquid crystal display device shown in FIG. 2A and 2B are explanatory diagrams showing a display pattern used in the viewing angle improvement process in the liquid crystal display device shown in FIG. 1, where FIG. 1A shows a display pattern when the intensity parameter is strong, and FIG. 2B shows a weak intensity parameter. The display pattern is shown. 2A and 2B are explanatory diagrams illustrating a viewing angle improvement process in the liquid crystal display device illustrated in FIG. 1, in which FIG. 1A illustrates a case where the viewing angle improvement process is performed on image data of a full screen display, and FIG. This shows a case where the viewing angle improvement processing is performed. 2A and 2B are explanatory diagrams illustrating a method for setting the polarity of an applied voltage for each sub-pixel in the liquid crystal display device illustrated in FIG. 1, in which FIG. 1A illustrates a case without viewing angle improvement processing, and FIG. Is shown. It is explanatory drawing which shows the relationship between the applied voltage with respect to a pixel electrode, and the ripple noise which arises in a counter electrode or common wiring, When (a) is a big change of the applied voltage with respect to a pixel electrode, (b) is with respect to a pixel electrode. The case where the applied voltage is small is shown. (A) And (b) is the image size of the display area used as the object of the viewing angle improvement process in the liquid crystal display device according to another embodiment of the present invention, and the strength of the viewing angle improvement process performed on the display area. It is explanatory drawing which shows these relationships. It is explanatory drawing which shows the example of the display pattern displayed at the time of a viewing angle improvement process in the liquid crystal display device concerning further another embodiment of this invention, (a) is a 1x1 display pattern, (b) is 2x1. The display pattern is shown. It is explanatory drawing which shows the setting method of the polarity of the applied voltage with respect to each sub pixel in the liquid crystal display device concerning further another embodiment of this invention, (a) shows dot inversion drive, (b) shows 2H dot inversion drive. ing. It is explanatory drawing which shows the method of a viewing angle improvement process. It is explanatory drawing which shows the fall (shadow) of the display quality which arises by a viewing angle improvement process.

Embodiment 1
An embodiment of the present invention will be described.

(1-1. Configuration of the liquid crystal display device 100)
(A) of FIG. 1 is explanatory drawing which shows schematic structure of the liquid crystal display device 100 concerning this embodiment, (b) is sectional drawing of the AA cross section shown to (a).

  As shown in FIG. 1A, the liquid crystal display device 100 includes an image processing unit 10, a power supply circuit 1, a timing controller 2, a gate driver 3, a source driver 4, and a liquid crystal panel 5. Further, as shown in FIG. 1B, a backlight 6 is provided on the back side of the liquid crystal panel 5 (the side opposite to the display surface).

  The power supply circuit 1 converts an input power supply voltage supplied from an external power supply (for example, a commercial power supply, a private power generation power supply, a charging device) into a voltage used in each block (each unit) of the liquid crystal display device 100 and converts each block To supply.

  The image processing unit 10 receives input image data (input images A, B, C,...) Input from an external device (for example, a device that outputs image data such as a PC (Personal Computer) or a TV tuner). Are subjected to a superimposition process and a viewing angle improvement process, which will be described later, and output the image data subjected to these processes to the timing controller 2.

  The timing controller 2 generates a control signal (gate drive signal, source drive signal) for causing the liquid crystal panel 5 to display an image corresponding to the image data input from the image processing unit 10, and the gate driver 3 and the source driver 4. Output to.

  The gate driver 3 controls the voltage applied to each gate bus line provided in the liquid crystal panel 5 on the basis of a control signal (gate drive signal) input from the timing controller 2, so that the gate bus line to be written is controlled. Switch periodically.

  The source driver 4 is provided in the liquid crystal display device 100 at a timing synchronized with the switching cycle of the gate bus line to be written by the gate driver 3 based on a control signal (source drive signal) input from the timing controller 2. A voltage corresponding to the image data is applied to the source bus line. In addition, the source driver 4 sets the polarity of the voltage applied to each source bus line to a reverse polarity for each adjacent source bus line (for each subpixel arranged in the extending direction of the gate bus line). However, the present invention is not limited to this. For example, the source driver 4 may set the polarity of the voltage applied to each source bus line to a reverse polarity for each of the plurality of source bus lines. That is, the source driver 4 sets the polarity of the voltage applied to each source bus line to a reverse polarity for each predetermined number (one or more) of subpixels arranged in the extending direction of the gate bus line.

  The liquid crystal panel 5 includes an optical sheet 11 such as a diffusion sheet that diffuses light incident from the backlight 6, a polarizing plate 12, a TFT substrate 13, a liquid crystal layer 14, a counter substrate 15, and a polarizing plate 16 from the backlight 6 side. Arranged in order.

  The backlight 6 includes an LED substrate 21 and a plurality of LEDs (light sources) 22 arranged on the surface of the LED substrate 21 on the liquid crystal panel 5 side. In addition, a reflection sheet 23 for reflecting the light emitted from the LEDs 22 to the liquid crystal panel 5 side is provided on the surface of the LED substrate 21 on the liquid crystal panel 5 side.

  As a result, the liquid crystal panel 5 controls the transmittance of light emitted from the LED 22 and passing through the liquid crystal panel 5 for each subpixel (picture element) according to the image data.

  In the present embodiment, the case where the liquid crystal display device 100 is a transmissive liquid crystal display device 100 that performs display using light emitted from the backlight 6 will be described. It may be a reflective liquid crystal display device that reflects the incident light and uses it as display light, and is a transflective liquid crystal display that combines the functions of a transmissive liquid crystal display device and the reflective liquid crystal display device. It may be a device.

  FIG. 2 is an explanatory diagram showing a schematic configuration of the liquid crystal panel 5. As shown in this figure, the liquid crystal panel 5 includes a plurality of source bus lines S connected to the source driver 4 and a plurality of gates connected to the gate driver 3 and arranged so as to intersect each source bus line S. And a bus line G. In addition, a subpixel sp is provided at each intersection between the gate bus line G and the source bus line S.

  As shown in FIG. 2, one of the color filters R (red), G (green), and B (blue) is attached to the position corresponding to each subpixel sp on the counter substrate 15. One pixel P is constituted by three subpixels sp. FIG. 2 shows a configuration (vertical stripe pattern) in which the RGB sub-pixels sp are arranged in a stripe pattern, but the arrangement method of the sub-pixels is not limited to this. For example, a delta pattern method in which RGB subpixels are arranged in a triangular shape may be used.

  Each subpixel sp is provided with a switching element 31 made of TFT (Thin Film Transistor). The gate terminal of each switching element 31 is a gate bus line G, the source terminal is a source bus line S, and the drain terminal is described later. The pixel electrodes 32 are connected to the pixel electrodes 32 respectively.

  FIG. 3 is an explanatory diagram schematically showing the configuration of the subpixel sp, and FIG. 4 is a cross-sectional view of the subpixel sp.

  As shown in these drawings, a gate bus line G, a common wiring 35, and a counter electrode 33 are formed on the TFT substrate 13, and a gate insulating film (insulating film) 17 is formed so as to cover these members. On the gate insulating film 17, the semiconductor film 34, the source bus line S, and the pixel electrode 32 are formed. That is, the pixel electrode 32 and the counter electrode 33 are disposed on the same substrate with the insulating layer (gate insulating film 17) interposed therebetween.

  The common wiring 35 is formed to extend substantially parallel to each gate bus line G, and the counter electrode 33 is connected to the common wiring 35. The common wiring 35 is connected to the source driver 4, and the potential of the common wiring 35 is controlled by the source driver 4 to the counter potential Vcom. Note that the counter electrode 33 and the common wiring 35 may be integrally formed.

  The semiconductor film 34 is disposed at a position facing the gate bus line G through the gate insulating film 17, and a part of the source bus line S and a part of the pixel electrode 32 are connected to the semiconductor film 34. As a result, the switching element 31 made of a TFT having the semiconductor film 34 as a channel layer is formed. In the present embodiment, an amorphous silicon film is used as the semiconductor film 34. However, the configuration of the semiconductor film 34 is not limited to this. For example, an oxide semiconductor such as an indium gallium zinc oxide semiconductor may be used, or polysilicon may be used.

  A protective oxide film 18 is formed so as to cover the source bus line S, the semiconductor film 34, and the pixel electrode 32, and an alignment film 19 is further formed so as to cover the protective oxide film 18.

  In addition, an alignment film 20 is formed on a surface of the counter substrate 15 facing the TFT substrate 13, and a polarizing plate 16 is disposed on the surface (display surface side) opposite to the surface facing the TFT substrate 13. Has been. Further, as described above, any one of R, G, and B color filters (not shown) is provided in a region corresponding to each subpixel in the counter substrate 15. The alignment films 19 and 20 regulate the alignment direction of the liquid crystal molecules when no electric field is applied.

  FIG. 5 is an explanatory diagram schematically showing the voltage applied between the pixel electrode 32 and the counter electrode 33 and the alignment state of the liquid crystal molecules, where (a) is the state when no voltage is applied, (b ) Shows a state when a voltage is applied. As shown in FIG. 5A, when no voltage is applied between the picture element electrode 32 and the counter electrode 33 and both the electrodes are at the same potential, the major axis direction of the liquid crystal molecules is the picture. It is oriented so as to face the direction orthogonal to the opposing direction of the elementary electrode 32 and the opposing electrode 33. On the other hand, when a voltage is applied between the pixel electrode 32 and the counter electrode 33, as shown in FIG. 5B, the liquid crystal molecules are applied to the substrate surface by the electric field formed between the two electrodes. Rotate along a parallel direction. As the direction of the liquid crystal molecules rotates in this way, the polarization axis of the light passing through the liquid crystal layer rotates. The rotation angle is determined according to the voltage applied between the pixel electrode 32 and the counter electrode 33.

  As shown in FIG. 1 (b), only light having a specific polarization axis direction is transmitted through the polarizing plate 12 and light having the same polarization axis passes through the liquid crystal layer 14 as shown in FIG. When passing, the polarization axis is shifted by the birefringence of the liquid crystal. The amount of deviation of the polarization axis depends on the amount of rotation of the liquid crystal molecules, and the amount of light transmitted through the liquid crystal panel 5 is determined according to the polarization axis of the light passing through the liquid crystal layer 14 and the polarization axis direction of the polarizing plate 16. . Since the amount of rotation of the liquid crystal molecules depends on the voltage applied between the pixel electrode 32 and the counter electrode 33, gradation display can be performed by controlling the voltage applied to the pixel electrode 32.

  FIG. 6 is a plan view showing the configuration of the subpixel shown in FIG. 3 in more detail. As shown in FIG. 6, the picture element electrode 32 and the counter electrode 33 are formed in a comb-teeth shape, and the comb-teeth portions of these electrodes are alternately arranged. Further, as shown in FIG. 6, each subpixel is provided with an auxiliary capacitance electrode 36 (see the hatched portion in the drawing) and an auxiliary capacitance wiring 37. The auxiliary capacitance line 37 is connected to the common line 35 through the contact hole 39 and supplied with the counter potential Vcom. The auxiliary capacitance electrode 36 is connected to the pixel electrode 32 through a contact hole 38. Thereby, a liquid crystal storage capacitor for holding the potential when the switching element 31 is turned off is formed between the storage capacitor electrode 36 and the storage capacitor wiring 37. In the example of FIG. 6, the auxiliary capacitance line 37 is connected to the common line 35. However, the present invention is not limited to this, and an auxiliary capacitance line is provided separately from the common line 35, and the auxiliary capacitance potential is provided via the auxiliary capacitance line. May be supplied.

  FIG. 7 is an equivalent circuit diagram of the subpixel structure shown in FIG. As shown in this figure, in the horizontal electric field type liquid crystal display device, the source electrode side of the picture element electrode 32 and the switching element 31 and the counter electrode 33 are arranged on the same substrate with an insulating layer sandwiched between them. Capacitive coupling (crosstalk capacitance) occurs at a portion where the source electrode side of the element electrode 32 and the switching element 31 and the counter electrode 33 face each other with the insulating layer interposed therebetween.

  In this embodiment, as shown in FIG. 8, the thickness of the liquid crystal layer 14 is about 3 μm, whereas the thickness of the gate insulating film 17 is only about 0.3 μm. Capacity increases.

  When such a crosstalk capacitance is generated, as shown in FIG. 9, when the switching element 31 is turned on (conductive state) and the potential of the pixel electrode 32 changes, the change passes through the crosstalk capacitance. 9 propagates to the counter electrode 33 and the common wiring 35, and ripple noise as shown in FIG. 9 occurs. This ripple noise is locally generated around the sub-pixel where the switching element 31 is turned on and writing is performed. The magnitude of the ripple noise depends on the magnitude of the potential change of the picture element electrode 32. In the case of a normally black liquid crystal panel, the magnitude of the ripple noise is greatest when polarity inversion occurs during display of the maximum gradation.

  Due to the influence of the ripple noise, as shown in FIG. 10A, the voltage charged in the liquid crystal capacitance when the switching element 31 is turned on (potential difference between the pixel electrode 32 and the counter electrode 33). Deviates from the original value.

  When the switching element 31 is in the OFF state (non-conducting state), since there is a liquid crystal auxiliary capacitor, the potential of the liquid crystal capacitor does not change as shown in FIG.

  The magnitude of the ripple noise depends on the magnitude of the voltage applied to the picture element electrode 32, and is maximized when polarity inversion occurs at the maximum gradation (luminance 100%). In addition, when the polarity deviation occurs in the subpixels arranged in the extending direction of the gate bus line, the ripple noise is not canceled between the subpixels, and the degree of shadowing is increased.

(1-2. Superimposition processing and viewing angle improvement processing)
As shown in FIG. 1A, the image processing unit 10 includes a superimposition processing unit 41, an intensity parameter selection unit 42, and a viewing angle improvement processing unit 43.

  The superimposition processing unit 41 generates a superimposed image by superimposing a plurality of input image data (input video data) input from the external device according to an instruction from the external device, and outputs the superimposed image to the viewing angle improvement processing unit 43. . At this time, the superimposition processing unit 41 performs superimposition after subjecting the input image data to enlargement processing or reduction processing as necessary. Further, the superimposition processing unit 41 generates information indicating the display position and display size of each superimposed image and outputs the information to the intensity parameter selection unit 42.

  FIG. 11 is an explanatory diagram illustrating an example of an image superimposed by the superimposition processing unit 41. In the example shown in this figure, the input image A is displayed with the full screen size of the display screen, and the input images B and C are superimposed on a part of the input image A with a display size smaller than the input image A. The number of input images to be superimposed, the display size of each image, and the display position of each image are not limited to this.

  Based on the information indicating the display position and display size of each image input from the superimposition processing unit 41, the intensity parameter selection unit 42 generates an intensity parameter indicating the intensity of the viewing angle improvement process applied to each image, and the viewing angle Output to the improvement processing unit 43.

  (A)-(f) of FIG. 12 is explanatory drawing which shows the viewing angle improvement process according to the setting method of an intensity parameter, and an intensity parameter.

  The intensity parameter selection unit 42 selects the strong level as the intensity parameter when there is no display area for displaying another image in the extending direction of the gate bus line with respect to the display area for performing the viewing angle improvement processing. That is, in the case of full screen display (display mode in which one image is displayed on the entire display screen) as shown in FIG. 12A, and viewing angle improvement processing is performed as shown in FIG. When the display area covers the entire extending direction of the gate bus line on the display screen (the left-right direction in the example of this figure), the strength parameter selection unit 42 selects the strong level as the strength parameter.

  In addition, as shown in FIGS. 12C to 12F, the intensity parameter selection unit 42 displays a display area for displaying another image in the extending direction of the gate bus line with respect to the display area for performing the viewing angle improvement process. Is present, the weak level is selected as the intensity parameter.

  Note that the user may arbitrarily set whether or not to perform the viewing angle improvement process on each display area, and the image (video) genre, the type of image data input source, and the size of the display area. The intensity parameter selection unit 42 or the viewing angle improvement processing unit 43 may set the display area based on conditions such as the arrangement position of the display area and a preset rule.

  The viewing angle improvement processing unit 43 applies an intermediate gradation image to the image data input from the superimposition processing unit 41 according to the intensity parameter input from the viewing angle improvement processing unit 43. A viewing angle improvement process is performed to convert the image into an image to be reproduced by a display pattern in which a tone subpixel and a subpixel having a higher gradation than the gradation are combined.

  Specifically, when the intensity parameter is strong with respect to the image data of the display area on which the viewing angle improvement process is performed, the viewing angle improvement processing unit 43 displays an intermediate gradation image as shown in FIG. Is converted into an image of a staggered pattern (display pattern in which the bright and dark parts are arranged in a staggered pattern) in which the luminance difference between the bright part and the dark part is in the range of 30% to 100%. Further, when the intensity parameter is weak, as shown in FIG. 13B, the intermediate gradation image is converted into a staggered pattern image in which the brightness difference between the bright part and the dark part is in the range of 0% to 30%. To do. That is, the viewing angle improvement processing unit sets a larger difference in gradation value between the low gradation subpixel and the high gradation subpixel in the display region targeted for the viewing angle improvement processing as the intensity parameter is larger. .

  Therefore, for example, as shown in FIG. 14A, when the viewing angle improvement processing is performed on the image data of the full screen display, the viewing angle improvement processing unit 43 brightens the display image having the gradation value of 50%. Is converted into a staggered pattern in which the luminance difference between the dark portion and the dark portion is 30% to 100% (100% in this example). In addition, as shown in FIG. 14B, when the viewing angle improvement processing is performed on the partial display image data in which the display area of another image exists in the extending direction of the gate bus line, the viewing angle improvement processing unit No. 43 converts a display image having a gradation value of 50% into a staggered pattern in which the luminance difference between the bright part and the dark part is 0 to 30% (20% in the example of this figure).

  In this embodiment, as shown in FIG. 15, the sub-pixels arranged in the extending direction of the source bus line (the vertical direction in the figure) are sub-pixels of the same color (R, G, or B). Yes. Further, in each frame period, a potential having the same polarity is applied to each sub-pixel arranged in the extending direction of the source bus line, and one sub-pixel is arranged in each sub-pixel arranged in the extending direction of the gate bus line (the left-right direction in the figure). A reverse polarity potential is applied to each pixel. In addition, the polarity of the potential applied to each subpixel is inverted every predetermined number of frames (every frame in this embodiment).

  Thus, when the viewing angle improvement process is not performed, as shown in FIG. 15A, the polarity of the applied voltage is not biased between the adjacent gate bus lines.

  On the other hand, when the viewing angle improvement processing is performed, as shown in FIG. 15B, the polarity of the applied voltage is biased between adjacent gate bus lines and between successive frames. For example, in the nth frame, odd-numbered gate bus lines are biased to positive polarity and even-numbered gate bus lines are biased to negative polarity, and in the (n + 1) th frame, odd-numbered gate bus lines are negative-polarity, even-numbered gates. Bus lines are biased toward positive polarity.

  FIG. 16 is an explanatory diagram showing the relationship between the voltage applied to the pixel electrode and the ripple noise generated in the counter electrode or common wiring. FIG. 16A shows a case where the change in the voltage applied to the pixel electrode is large, and FIG. The case where the applied voltage with respect to an elementary electrode is small is shown. As shown in FIG. 16, the larger the change in the voltage applied to the pixel electrode, the greater the ripple noise generated in the counter electrode or common wiring.

  Therefore, in this embodiment, as described above, the viewing angle improvement processing unit 43 has a luminance difference between the bright part and the dark part of 30% to 30% when there is no other image display area in the extending direction of the gate bus line. The viewing angle improvement process is performed using a staggered pattern that is 100% and, if present, a staggered pattern in which the brightness difference between the bright part and the dark part is 0 to 30%. That is, when there is no other image display area in the extending direction of the gate bus line, the degree of viewing angle improvement processing is increased, and when it is present, the degree of viewing angle improvement processing is decreased.

  Thereby, when there is no other image display area in the extending direction of the gate bus line and it is not necessary to consider the suppression of shadow, a larger viewing angle improvement effect can be obtained.

  In addition, when there is a display area for another image in the extending direction of the gate bus line, the bias of the applied voltage to each subpixel on the gate bus line and the application are reduced by reducing the degree of the viewing angle improvement processing. It is possible to reduce the amount of change in voltage and reduce ripple noise to prevent the deterioration of image quality such as shadow in the display area of other images, and to obtain the effect of improving the viewing angle.

[Embodiment 2]
Another embodiment of the present invention will be described. For convenience of explanation, members having the same functions as those described in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and description thereof is omitted.

  In the first embodiment, the configuration in which the intensity parameter of the viewing angle improvement process is set in two stages of “strong” and “weak” has been described. On the other hand, in the present embodiment, the intensity of the viewing angle improvement process is set in more stages (or set continuously) in accordance with the size of the display area that is the target of the viewing angle improvement process.

  FIG. 17A shows the relationship between the image size in the extending direction of the gate bus line of the display area targeted for the viewing angle improvement process and the intensity parameter of the viewing angle improvement process applied to the display area. It is a graph. FIG. 17B is an explanatory diagram showing the relationship between the display area and the strength of the viewing angle improvement processing performed on the display area.

  As shown in FIGS. 17A and 17B, the intensity parameter selection unit 42 extends the gate bus line of the image based on the information indicating the display size of each image input from the superimposition processing unit 41. The size in the direction is specified, and the strength parameter is set so that the strength of the viewing angle improvement processing becomes weaker as the size in the extending direction of the gate bus line is larger. That is, the intensity parameter selection unit 42 sets the intensity parameter of the viewing angle improvement process to be smaller as the width of the display area targeted for the viewing angle improvement process in the extending direction of the gate bus line is wider. However, when the width of the display area covers the entire area of the gate bus line in the display screen, the strength of the viewing angle improvement processing for the display area is set to the maximum.

  Thereby, the viewing angle improvement effect can be more suitably obtained while appropriately preventing the deterioration of image quality such as shadow.

  In other words, the larger the image size in the extending direction of the gate bus line of the display area to be subjected to the viewing angle improvement process, the more likely the shadow is generated in the other area aligned in the extending direction of the gate bus line with respect to the display area. . In contrast, in the present embodiment, by setting the intensity of the viewing angle improvement process according to the size of the display area as described above, the intensity of the viewing angle improvement process is reduced as the condition is likely to cause shadowing. The effect of improving the viewing angle can be obtained while appropriately suppressing the occurrence of shadows. Further, in the case where shadows are unlikely to occur, the strength of the viewing angle improvement process can be increased to obtain a larger viewing angle improvement effect.

  Note that the relationship between the display area targeted for the viewing angle improvement processing and the intensity parameter of the viewing angle improvement processing is not limited to a linear relationship (proportional relationship) as shown in FIG. What is necessary is just to set or adjust suitably according to the display characteristic etc. of the liquid crystal panel 5.

[Embodiment 3]
Still another embodiment of the present invention will be described. For convenience of explanation, members having the same functions as those described in the above-described embodiment are denoted by the same reference numerals as those of the embodiment, and description thereof is omitted.

  In the present embodiment, the intensity parameter of the viewing angle correction process is set according to the genre of the input image data or the type of the input source (source) of the input image data.

  In addition to the information indicating the display position and display size of each display area, the superimposition processing unit 41 outputs information indicating the genre and input source of the input image corresponding to each display area to the intensity parameter selection unit 42.

  The information indicating the video genre may be determined based on information added to the input image data. For example, in the case of image data of digital TV broadcast, it can be determined using information incorporated in program information as meta information. Further, the information indicating the input source may be determined based on, for example, information added to the image data, or may be determined according to the input terminal. In the case of HDMI (registered trademark), device cooperation information You may judge using.

  The intensity parameter selection unit 42 sets the intensity parameter of the viewing angle improvement process for the input image according to the genre and input source of the input image.

  Specifically, a storage unit (not shown) that stores a lookup table in which a plurality of genres and intensity parameter setting methods corresponding to each genre are associated is provided, and the intensity parameter selection unit 42 includes: An intensity parameter setting method corresponding to the genre indicated by the information input from the superimposition processing unit 41 is read from the lookup table, and the intensity parameter is set based on the setting method. In addition, a storage unit (not shown) that stores a lookup table in which a plurality of input source types and intensity parameter setting methods are associated with each other is provided. An intensity parameter setting method corresponding to the type of the input source indicated by the input information is read from the lookup table, and the intensity parameter is set based on the setting method.

  For example, when the genre is martial arts (for example, sumo wrestling, professional wrestling, boxing, etc.), if the change in skin color due to viewing angle dependency is large, the discomfort given to the user is greater than the above-mentioned adverse effects of shadows. Is set to a value larger than normal (a value at which the degree of the viewing angle improvement processing becomes stronger).

  In addition, when the genre is a dish (for example, a cooking program, a gourmet program, etc.), if the change in the color of the cooking due to the viewing angle dependency is large, the discomfort given to the user is greater than the above-described adverse effects of the shadow. Is set to a value larger than normal.

  Further, when the genre is a character, in order to prioritize the visibility of the character, the intensity parameter is set to a value smaller than that in the normal state to suppress the occurrence of the above-described shadow.

  When the input source is a PC (Personal Computer), the user often reads characters at a position close to the front of the screen. Therefore, the viewing angle improvement processing is set to off or the intensity parameter is set to normal. The value is set smaller than the time, giving priority to the fineness of characters and suppressing the occurrence of shadows.

  In addition, when the input source is a game machine, a decrease in response speed due to the viewing angle improvement process may give the user a sense of incongruity. Therefore, the intensity parameter is set to a value smaller than normal, and the above-described shadow Suppresses the occurrence.

  That is, in the liquid crystal display device, so-called overdrive driving is generally performed in which a voltage higher than the applied voltage corresponding to the original display luminance is applied in order to improve the response speed when performing moving image display. However, when the viewing angle improvement process is performed, the display brightness of the intermediate gradation before the viewing angle improvement process is divided into a brightness higher and lower than the brightness (for example, the display brightness 50% before the viewing angle improvement process is reduced to the display brightness). Since the display is performed after being decomposed into 0% and 100%, a luminance higher than the display luminance before the viewing angle improvement processing is used. For this reason, overdrive driving cannot be performed properly, and the response speed may decrease. Therefore, in the case of a genre that needs to emphasize response speed, by setting the strength parameter to a value smaller than normal, it is possible to suppress a decrease in response speed and to suppress the occurrence of the above-described shadow.

  It should be noted that how much intensity is added to the intensity parameter of the viewing angle improvement process according to the genre or the input source may be appropriately set or adjusted according to the display characteristics of the liquid crystal panel 5 or the like.

[Embodiment 4]
Still another embodiment of the present invention will be described. For convenience of explanation, members having the same functions as those described in the above-described embodiment are denoted by the same reference numerals as those of the embodiment, and description thereof is omitted.

  In each of the above-described embodiments, when the viewing angle improvement process is performed, a bright portion (high gradation subpixel) and a dark portion (for each subpixel) in both the extending direction of the gate bus line and the extending direction of the source bus line ( The configuration (see FIG. 15B) using a display pattern (1 × 1 staggered pattern) alternately arranged with sub-pixels of low gradation has been described.

  On the other hand, in this embodiment, the display pattern at the time of viewing angle improvement processing is made different between the case of full screen display and the case of partial display.

  That is, in the case where the size of the display area to be subjected to the viewing angle improvement process in the extending direction of the gate bus line extends over the entire area in the display screen, as shown in FIG. A display pattern (1 × 1 staggered pattern) in which bright portions and dark portions are alternately arranged for each sub-pixel in both the extending direction and the extending direction of the source bus line is used.

  On the other hand, when the size of the display area to be subjected to the viewing angle improvement process with respect to the extending direction of the gate bus line is only a part of the display screen in the extending direction, as shown in FIG. With respect to the extending direction of the bus line, a bright portion and a dark portion are alternately arranged every two sub-pixels, and with respect to the extending direction of the source bus line, a bright portion and a dark portion are alternately arranged every sub-pixel. 2 × 1 staggered pattern).

  In other words, in the present embodiment, when the display area for performing the viewing angle improvement process is only a part of the extending direction of the gate bus line on the display screen of the liquid crystal panel 5, each sub line arranged in the extending direction of the gate bus line is arranged. Display of low-gradation subpixels and high-gradation subpixels so that the polarity of the applied voltage polarity with respect to the pixels is smaller than when the display area where the viewing angle improvement processing is performed extends over the entire extending direction of the gate bus line. A pattern (display pattern used for viewing angle improvement processing) is set.

  As a result, when the size of the display area of the display area subject to the viewing angle improvement process is a part of the same direction in the display screen, the application to each subpixel in the extension direction of the gate bus line It is possible to suppress the bias of the polarity of the voltage and suppress the occurrence of shadow. That is, it is possible to obtain a viewing angle improvement effect while suppressing the occurrence of shadows.

  In addition, when the size of the display area of the display area subject to the viewing angle improvement process in the extending direction of the gate bus line covers the entire area of the display screen, it is not necessary to consider the occurrence of shadows. A display pattern in which bright portions and dark portions are alternately arranged for each subpixel in both the extending direction and the extending direction of the source bus line is used. Thereby, a viewing angle improvement effect can be obtained and high-definition display can be performed.

  In the present embodiment, the configuration using the 1 × 1 display pattern and the 2 × 1 display pattern during the viewing angle improvement processing has been described. However, the present invention is not limited to this, and for example, the 1 × 2 display pattern A 2 × 2 display pattern or the like may be used.

  In addition, the finer the display pattern of the bright and dark areas in the viewing angle improvement process, the closer the display pattern is to 1 × 1, and the higher the resolution, the smaller the polarity, the smaller the bias of the polarity. It is preferable to set the display pattern finely for difficult conditions, and to set the display pattern coarsely for conditions where shadows are likely to occur.

[Embodiment 5]
Still another embodiment of the present invention will be described. For convenience of explanation, members having the same functions as those described in the above-described embodiment are denoted by the same reference numerals as those of the embodiment, and description thereof is omitted.

  In each of the above-described embodiments, in each frame period, a potential having the same polarity is applied to each subpixel arranged in the extending direction of the source bus line, and each subpixel arranged in the extending direction of the gate bus line is applied to each subpixel. The configuration (column line inversion driving) in which the potential of the reverse polarity is applied and the polarity of the potential applied to each subpixel is inverted every frame has been described.

  On the other hand, in this embodiment, a method different from the column line inversion driving is used as a method for setting the polarity of the applied voltage to each subpixel.

  For example, as shown in FIG. 19A, in each frame period, a potential having a reverse polarity is applied to each sub-pixel arranged in the extending direction of the source bus line for each sub-pixel, and in the extending direction of the gate bus line. A driving method (dot inversion driving) may be used in which a potential having a reverse polarity is applied to each subpixel arranged for each subpixel, and the polarity of the potential applied to each subpixel is reversed every frame.

  Further, as shown in FIG. 19B, in each frame period, a potential having a reverse polarity is applied to each sub-pixel arranged in the extending direction of the source bus line every two sub-pixels, and the extending direction of the gate bus line is increased. A driving method (2H dot inversion driving) may be used in which a reverse polarity potential is applied to each of the arranged subpixels for each subpixel, and the polarity of the potential applied to each subpixel is inverted every frame.

  Even if each of these driving methods is used, it is possible to obtain the effect of improving the viewing angle characteristics substantially the same as in the above-described embodiments. Note that in the case of column line inversion driving, the number of times of inversion of the applied voltage to each source bus line during each frame period can be reduced, which has the advantage that power consumption can be reduced.

  In each of the above embodiments, the present invention has been described with reference to an example in which the present invention is applied to a liquid crystal panel (a so-called lateral electric field type liquid crystal panel) in which a pixel electrode and a counter electrode are formed on the same substrate. However, the present invention is not limited to this, and the present invention may be applied to a liquid crystal panel (so-called vertical electric field type liquid crystal panel) in which both electrodes are formed on different substrates.

[Summary]
The liquid crystal display device 100 according to the first aspect of the present invention includes a plurality of gate bus lines, a plurality of source bus lines intersecting with the gate bus lines, and an intersection of the gate bus lines and the source bus lines. In the liquid crystal display device 100 including the liquid crystal panel 5 having the provided picture elements, an intermediate gray scale image is input from the gray scale picture element lower than the gray scale and the gray scale for the input image data. A viewing angle improvement processing unit 43 for performing a viewing angle improvement process for converting the image into a reproducible image by a display pattern combined with a high gradation picture element, and an intensity parameter selection for setting an intensity parameter of the viewing angle improvement process. The strength parameter selection unit 42 includes a display area where the viewing angle improvement process is performed in a part of the extending direction of the gate bus line on the display screen of the liquid crystal panel 5. The intensity parameter is set smaller than in the case where the gate bus line extends in the entire extending direction, and the viewing angle improvement processing unit 43 increases the intensity of the low-gradation picture element and the higher order. It is characterized by setting a large difference in gradation value from the tone picture element.

  According to the above configuration, when the display area for performing the viewing angle improvement process is only a part in the extending direction of the gate bus line on the display screen of the liquid crystal panel 5, the low gradation picture element and the high gradation picture element are displayed. By setting the difference in the gradation value to be small, it is possible to reduce the bias of the polarity of the applied voltage with respect to the pixels arranged in the extending direction of the gate bus line. Thereby, it is possible to obtain the effect of improving the viewing angle while reducing the crosstalk generated between the pixel electrode 32 and the counter electrode 33 during the viewing angle improving process and suppressing the occurrence of shadow. In addition, when the display area where the viewing angle improvement process is performed extends over the entire extension direction of the gate bus line, the difference in the gradation value between the low gradation picture element and the high gradation picture element is set to be larger. A large viewing angle improvement effect can be obtained.

  The liquid crystal display device 100 according to the second aspect of the present invention is the pixel electrode according to the first aspect, wherein each of the picture elements is disposed on the same substrate (TFT substrate 13) with an insulating layer (gate insulating film 17) interposed therebetween. 32 and the counter electrode 33 may be provided.

  In the case where the pixel electrode 32 and the counter electrode 33 are arranged on the same substrate (TFT substrate 13) with the insulating layer (gate insulating film 17) interposed therebetween, the pixel electrode 32 and the counter electrode 33 are arranged between the pixel electrode 32 and the counter electrode 33. Crosstalk is particularly likely to occur, and shadows are likely to occur during viewing angle improvement processing. On the other hand, according to the above configuration, it is possible to reduce the crosstalk between the picture element electrode 32 and the counter electrode 33 and suppress the occurrence of shadow.

  In the liquid crystal display device 100 according to the third aspect of the present invention, in the first or second aspect, the intensity parameter selection unit 42 is configured to extend the gate bus line on the display screen of the liquid crystal panel 5 in which the display area for performing the viewing angle improvement process is In the case of only a part of the direction, the strength parameter is set to be smaller as the width of the display region in the extending direction of the gate bus line is wider.

  According to the above configuration, by setting the strength of the viewing angle improvement processing according to the width of the display area where the viewing angle improvement processing is performed in the extension direction of the gate bus line, it is possible to appropriately generate shadows due to crosstalk. And a larger viewing angle improvement effect can be obtained.

  In the liquid crystal display device 100 according to the aspect 4 of the present invention, in any one of the aspects 1 to 3, the intensity parameter selection unit 42 is configured to adjust the intensity parameter according to the genre of the input image data.

  According to the above configuration, it is possible to adjust which of the viewing angle improvement effect and the shadow suppression effect should be emphasized according to the genre of the input image data. In other words, depending on the genre of the input image data, in the case of a genre where the viewing angle improvement effect should be more important than the shadow suppression effect, the intensity parameter should be set larger, and the shadow suppression effect more important than the viewing angle improvement processing effect. In the case of a genre to be used, the intensity parameter can be set small.

  In the liquid crystal display device 100 according to the fifth aspect of the present invention, in any one of the first to fourth aspects, the intensity parameter selection unit 42 adjusts the intensity parameter according to the type of input source of the input image data. is there.

  According to the above configuration, it is possible to adjust which of the viewing angle improvement effect and the shadow suppression effect should be emphasized according to the type of the input source of the input image data. That is, depending on the type of input source of the input image data, in the case of a genre where the viewing angle improvement effect should be more important than the shadow suppression effect, the intensity parameter is set larger, and the shadow suppression than the viewing angle improvement processing effect is set. In the case of a genre where the effect should be emphasized, the intensity parameter can be set small.

  The liquid crystal display device 100 according to the sixth aspect of the present invention is the liquid crystal display device 100 according to any one of the first to fifth aspects, wherein the viewing angle improvement processing unit includes a gate bus line on the display screen of the liquid crystal panel. When the display area is only a part of the extending direction of the gate bus line, the bias of the polarity of the applied voltage to each pixel arranged in the extending direction of the gate bus line is such that the display area for performing the viewing angle improvement process extends over the entire extending direction of the gate bus line. The display pattern is set to be smaller than the case.

  According to the above configuration, when the display area for performing the viewing angle improvement process is only a part of the extending direction of the gate bus line on the display screen of the liquid crystal panel 5, the pixel electrode and the counter electrode are The occurrence of shadows can be suppressed while reducing the crosstalk generated during the period. Further, when the display area where the viewing angle improvement process is performed covers the entire extending direction of the gate bus line, a larger viewing angle improvement effect can be obtained.

  The control method of the liquid crystal display device 100 according to the aspect 7 of the present invention includes a plurality of gate bus lines, a plurality of source bus lines intersecting with the gate bus lines, and an intersection of the gate bus lines and the source bus lines. A method of controlling a liquid crystal display device including a liquid crystal panel 5 having a picture element provided for each unit, wherein an intermediate gray scale image is lower than a gray scale picture element for input image data. And a viewing angle improvement process step for performing a viewing angle improvement process for converting the image into an image that reproduces the image using a display pattern that combines a pixel with a higher gradation than the gradation, and an intensity parameter for the viewing angle improvement process. The strength parameter selection step, and in the strength parameter selection step, the display area where the viewing angle improvement processing is performed is the extending direction of the gate bus line on the display screen of the liquid crystal panel In the case where it is only a part, the intensity parameter is set to be smaller than the case where the gate bus line extends in the entire extending direction, and in the viewing angle improvement processing step, the lower the gradation parameter, the larger the intensity parameter is. It is characterized in that a difference in gradation value from the high gradation picture element is set large.

  According to the above method, when the display area for performing the viewing angle improvement process is only a part of the extending direction of the gate bus line on the display screen of the liquid crystal panel 5, the effect of improving the viewing angle is suppressed while suppressing the occurrence of shadow. Can be obtained. In addition, when the display area where the viewing angle improvement process is performed extends over the entire extension direction of the gate bus line, the difference in the gradation value between the low gradation picture element and the high gradation picture element is set to be larger. A large viewing angle improvement effect can be obtained.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The present invention can be applied to a liquid crystal display device that performs a viewing angle improvement process.

DESCRIPTION OF SYMBOLS 1 Power supply circuit 2 Timing controller 3 Gate driver 4 Source driver 5 Liquid crystal panel 6 Backlight 10 Image processing part 13 TFT substrate 15 Opposite substrate 17 Gate insulating film (insulating film)
31 switching element 32 picture element electrode 33 counter electrode 41 superimposition processing unit 42 intensity parameter selection unit 43 viewing angle improvement processing unit 100 liquid crystal display device

Claims (7)

A liquid crystal panel having a plurality of gate bus lines, a plurality of source bus lines intersecting with each of the gate bus lines, and a picture element provided at each intersection of the gate bus line and the source bus line is provided. A liquid crystal display device,
The input image data, the display pattern of a combination of a picture element of high gradation than the picture element and the intermediate gray low image halftone than the halftone gradation image which reproduces the image A viewing angle improvement processing unit for performing a viewing angle improvement process to be converted;
An intensity parameter selection unit for setting the intensity parameter of the viewing angle improvement process,
The intensity parameter selection unit is configured so that when the display area for performing the viewing angle improvement process is only a part of the extending direction of the gate bus line on the display screen of the liquid crystal panel, the display area of the liquid crystal panel extends over the entire extending direction of the gate bus line. Set the intensity parameter small,
The viewing angle improvement processing unit sets a larger difference in gradation value between the low gradation picture element and the high gradation picture element as the intensity parameter increases.   2. The liquid crystal display device according to claim 1, wherein each of the picture elements includes a picture element electrode and a counter electrode arranged on the same substrate with an insulating layer interposed therebetween. The intensity parameter selection unit
When the display area for performing the viewing angle improvement process is only a part of the extending direction of the gate bus line in the display screen of the liquid crystal panel, the larger the width of the display area in the extending direction of the gate bus line, The liquid crystal display device according to claim 1, wherein the liquid crystal display device is set small. The intensity parameter selection unit
4. The liquid crystal display device according to claim 1, wherein the intensity parameter is adjusted according to a genre of input image data. The intensity parameter selection unit
5. The liquid crystal display device according to claim 1, wherein the intensity parameter is adjusted according to a type of an input source of the input image data. The viewing angle improvement processing unit
When the display area where the viewing angle improvement processing is performed is only a part of the extending direction of the gate bus line on the display screen of the liquid crystal panel, there is a bias in the polarity of the applied voltage to each pixel arranged in the extending direction of the gate bus line. 6. The display pattern according to claim 1, wherein the display pattern is set so that a display area where the viewing angle improvement process is performed is smaller than a case where the display area extends in the whole extending direction of the gate bus line. Liquid crystal display device. A liquid crystal panel having a plurality of gate bus lines, a plurality of source bus lines intersecting with each of the gate bus lines, and a picture element provided at each intersection of the gate bus line and the source bus line is provided. A method of controlling a liquid crystal display device,
The input image data, the display pattern of a combination of a picture element of high gradation than the picture element and the intermediate gray low image halftone than the halftone gradation image which reproduces the image A viewing angle improvement process for performing a viewing angle improvement process to be converted;
Including an intensity parameter selection step for setting an intensity parameter of the viewing angle improvement process,
In the intensity parameter selection step, when the display area for performing the viewing angle improvement process is only a part of the extending direction of the gate bus line on the display screen of the liquid crystal panel, it is more than in the case of extending over the entire extending direction of the gate bus line. Set the intensity parameter small,
In the viewing angle improvement processing step, the larger the intensity parameter is, the larger the difference in gradation value between the low gradation picture element and the high gradation picture element is set. .

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