JP2007163843A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a liquid crystal display device 1 having a changeable viewing angle without complicating the configuration of a liquid crystal panel, increasing the thickness and power consumption of the panel, and adding many hardware resources. <P>SOLUTION: The liquid crystal display device 1 is provided with: a liquid crystal panel 2 for gradation display; a viewing angle information input part 9 for receiving the information of a requested viewing angle; and a viewing angle changing means 7 for changing a viewing angle of a display image by changing a color of a part of the display image displayed on the liquid crystal panel 2 in accordance with the requested viewing angle inputted to the viewing angle information input part 9. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device in which a viewing angle of a liquid crystal panel can be selectively changed.

  A liquid crystal display device is a thin, light, and low power consumption display device, and is widely used in OA equipment such as an image display device such as a television and a personal computer.

  In general, a liquid crystal panel of a liquid crystal display device has a narrow viewing angle compared to other display devices (for example, CRT). This is because the liquid crystal panel uses liquid crystal alignment for display, and the relationship between the orientation of the liquid crystal alignment and the viewing angle affects the transmittance and the reflectance. On the other hand, various methods for expanding the viewing angle, such as an alignment division method, an IPS (in-plane switching) method, a VA (vertical alignment) method, or a retardation film disposed between the polarizing filter and the liquid crystal layer. Various methods have also been proposed and put into practical use.

  The liquid crystal display device preferably has a wide viewing angle when used by a large number of people, such as a television. However, the liquid crystal display device is not suitable for use in a public environment such as a mobile terminal, a mobile phone, or a laptop computer. It is desirable that the viewing angle is narrow in a usage pattern that the three parties do not want to see. As described above, which of the wide viewing angle and the narrow viewing angle is desirable depends on the usage form of the liquid crystal display device.

  Also, for example, when a television is displayed on a mobile terminal, it is desirable to have a narrow viewing angle in a situation where the television is viewed alone on a crowded train, but the television is viewed together with friends. In such a use situation, it is desirable to have a wide viewing angle. As described above, it may be desirable to selectively change the viewing angle to a wide viewing angle or a narrow viewing angle depending on the usage state of the liquid crystal display device.

  Prior arts related to a liquid crystal display device capable of selectively changing the viewing angle as described above include the following prior arts 1 and 2.

<Prior Art 1>
In the liquid crystal display device according to this prior art 1 (Patent Document 1), gamma conversion means for converting an input image signal as an output signal having a plurality of different gamma characteristics, and an image signal applied to the same pixel. Means for switching and controlling the gamma characteristics every n frames (n is a natural number of 2 or more), and corresponding pixels of a certain consecutive n frames have a display signal voltage corresponding to the same gamma characteristics and continuous frames. The display signal voltages having different polarities are applied and controlled so that the liquid crystal is driven so as to widen the viewing angle in accordance with the output of the gamma conversion means, which complicates the TFT manufacturing process and the panel manufacturing process. Without changing the viewing angle, the display signal is spatiotemporally modulated by applying a signal voltage with different gamma characteristics to each pixel every frame or every few frames. It is made possible to a large is.

<Conventional technology 2>
In the liquid crystal display device according to the related art 2 (Patent Document 2), a drive signal generation unit and a look for adjusting visual distortion of a gradation curve indicating a relationship between a gradation and a luminance ratio in a display image of a liquid crystal panel An up table is provided, and the distortion due to the viewing angle of the gradation curve is adjusted by the distortion adjusting means, thereby realizing a wide viewing angle or a narrow viewing angle.

Japanese Patent No. 3202450 JP 2003-295160 A

  In the prior arts 1 and 2 described above, both the gamma characteristic for the wide viewing angle and the gamma characteristic for the narrow viewing angle are divided and used spatially or temporally.

  In the case of using spatial division, specifically, one pixel is divided into a plurality of parts and each has a different gamma characteristic. In this case, it is necessary to drive each of the divided pixels. There are drawbacks in that the configuration of the liquid crystal panel is complicated, the thickness is increased, and the power consumption is increased.

  On the other hand, when using time division, specifically, different gamma characteristics are given in units of several frames. In this case, there is a drawback that flicker and flickering are easily noticeable.

  In either case, there is a drawback that a table or the like for holding information on a plurality of gamma characteristics is required.

  Also, when converting an input image with gamma characteristics, there is a drawback that a lot of hardware resources are required. For example, in the case of a color liquid crystal (RGB = 666), 18-bit bus width look-up tables are required for the number of gamma characteristics in the address space of 262144, and a correspondingly large capacity memory is required.

  Therefore, the present invention has been made to solve the above-described problems, and without complicating the configuration of the liquid crystal panel, increasing the thickness, and increasing the power consumption, it also requires a lot of hardware resources. An object is to obtain a liquid crystal display device in which the viewing angle can be changed without adding.

  In order to solve the above problems, the invention according to claim 1 is a liquid crystal panel capable of gradation display, a viewing angle information input unit for inputting information of a required viewing angle, and an input to the viewing angle information input unit. Viewing angle changing means for changing the viewing angle of the display image by changing the color of a part of the display image displayed on the liquid crystal panel in accordance with the requested viewing angle.

  According to the first aspect of the present invention, the color of a part of the display image displayed on the liquid crystal panel is changed in accordance with the required viewing angle input to the viewing angle information input unit, and the viewing angle of the display image is changed. Therefore, a liquid crystal display device capable of changing the viewing angle without complicating the configuration of the liquid crystal panel, increasing the thickness and power consumption, and without adding many hardware resources is obtained. Can do.

<Principle of the invention>
The present invention is a liquid crystal display device that can selectively change the viewing angle of a display image on a liquid crystal panel using the viewing angle characteristics of a general liquid crystal panel capable of gradation display.

  First, the viewing angle characteristics of a general liquid crystal panel capable of gradation display will be described. Here, the number of gradations of the liquid crystal panel is 64. For example, the minimum gradation 0 is the darkest gradation and the maximum gradation 63 is the brightest gradation.

  FIG. 1 is a graph showing the relationship between the viewing angle and the luminance of a liquid crystal panel.

  The vertical axis of the graph in FIG. 1 is the luminance, and the horizontal axis is the viewing angle. The viewing angle represents the viewing angle viewed from the front as 0 °, the viewing angle viewed from the left as-, and the viewing angle viewed from the right as +. Each curve in the graph of FIG. 1 is a characteristic curve at each gradation of every 16 gradations. The lower curve corresponds to a smaller gradation, and the upper curve corresponds to a larger gradation.

  From FIG. 1, it can be seen that the luminance becomes maximum at any viewing angle of 0 ° and decreases as the viewing angle approaches ± 80 °.

  FIG. 2 is a graph showing the relationship between the gradation and the luminance of the liquid crystal panel.

  The vertical axis of the graph in FIG. 2 is the luminance (normalized luminance obtained by normalizing with the luminance of white luminance (V63 gradation) here), and the horizontal axis is the gradation. Each curve in the graph of FIG. 2 is a characteristic curve at each viewing angle (in the graph, from 20 ° viewing angle (viewing angle viewed from the front) to −80 ° (viewing angle viewed from the left) every 20 ° for convenience. Only the characteristic curves at the five viewing angles are shown).

  In the graph of FIG. 2, the characteristic curve at each viewing angle has a larger downward curve as the viewing angle goes to 0 °, and the lower curve becomes smaller as the viewing angle goes to −80 °. .

  From this, when comparing the luminance difference between the maximum gradation 63 and, for example, the minimum gradation 0 and the intermediate gradation (for example, 15 to 55), in the case of the minimum gradation 0, the viewing angle 0 ° side (that is, the liquid crystal panel Both the front side and the viewing angle −80 ° side (that is, the lateral side of the liquid crystal panel) are large without much difference. However, in the case of intermediate gradation, the viewing angle becomes −80 ° side (that is, the front side of the liquid crystal panel). It can be seen that there is a characteristic that it becomes smaller as it goes to the ° side (that is, the side of the liquid crystal panel), and there is a large difference between the viewing angle 0 ° side and the −80 ° side.

  FIG. 3 is a graph showing the relationship between the viewing angle and the luminance of the liquid crystal panel.

  The vertical axis of the graph of FIG. 3 is luminance (here, normalized luminance obtained by normalization with luminance of white luminance (V63 gradation)), and the horizontal axis is the viewing angle. The viewing angle represents the viewing angle viewed from the front as 0 °, the viewing angle viewed from the left as-, and the viewing angle viewed from the right as +. Each curve in the graph is a characteristic curve at each gradation (here, for convenience, only characteristic curves at seven gradations from gradation 0 to gradation 63 are described at predetermined intervals) A higher gradation corresponds to the upper characteristic curve, and a lower gradation corresponds to the lower characteristic curve.

  In the graph of FIG. 3, the characteristic curve at each gradation is curved downward at a viewing angle of about 0 °, and the degree of curvature is larger as the characteristic curve at the intermediate gradation, and the characteristic at the maximum gradation 63 side. The curve and the characteristic curve on the minimum gradation 0 side are smaller.

  Accordingly, as in the case of FIG. 2, for example, when the luminance difference between the minimum gradation 0 and the intermediate gradation and the maximum gradation 63 is compared, in the case of the minimum gradation 0, the viewing angle 0 ° side (that is, the liquid crystal The front of the panel) and the viewing angle ± 80 ° side (that is, the side of the liquid crystal panel) are large without much difference, but in the case of intermediate gradation, the viewing angle increases toward the 0 ° viewing angle (ie, the front of the liquid crystal panel). It can be seen that there is a characteristic that it becomes smaller as it goes to the −80 ° side (that is, the side of the liquid crystal panel), and there is a large difference between the viewing angle 0 ° side and the viewing angle ± 80 ° side.

  From the above results (particularly FIGS. 2 and 3), by changing the color (in this case, the color gradation) of a part of the display image displayed on the liquid crystal panel using the above characteristics (more details) Change the color of a part of the display image (here, the gradation of the color) so that the difference between the brightness of the color (here, the brightness of the gradation) and the brightness of the remaining color of the display image increases. Thus, it can be seen that the visibility of the part of the display image, that is, the viewing angle of the display image can be changed to a wide viewing angle (or a narrow viewing angle). In the liquid crystal display device of the present application, the viewing angle of the display image can be selectively changed using this principle. Here, in general, as the difference between the luminance of the color of the part and the luminance of the color of the remaining part increases (or decreases) with respect to a part and the remaining part of the display image, the visibility of the part is increased. Take advantage of being high (or low).

<Structure of the invention>
A liquid crystal display device according to an embodiment of the present invention will be described.

  The liquid crystal display device according to this embodiment is applied to, for example, a display screen of a mobile phone, and the display image G (FIG. 5) displayed on the liquid crystal panel as the required viewing angle from the user increases (or decreases). ) (A part of an object that is not desired to be visually recognized by a third party) G1 color gradation, and the difference between the luminance of the gradation and the remaining part of the display image G (for example, the background part) G2 increases. By changing so as to (or decrease), the visibility of a part G1 of the display image, that is, the viewing angle of the display image G can be changed to a wide viewing angle (or a narrow viewing angle).

  As shown in FIG. 4, the liquid crystal display device 1 controls a liquid crystal panel 2 that can display a general gradation, a backlight 3 that illuminates the liquid crystal panel 2, a backlight power source 4, and a backlight power source 4. A power supply control unit for backlight (backlight control means) 5 and each object portion (character, pattern, design, etc.) G1, G3 and background portion G2 in the display image G (FIG. 5) displayed on the liquid crystal panel 2 The color information holding unit 6 that holds the color information, the image data generation unit (viewing angle changing means) 7 that generates image data based on the color information of the color information holding unit 6, and the image data generation unit 7 An image data transmitting unit 8 for transmitting image data to the liquid crystal panel 2; a user interface unit (viewing angle information input unit) 9 for inputting information on a required viewing angle of the liquid crystal panel 2 by a user; Based on the request viewing angle information input to the centers face portion 9, and a control unit 10 for controlling the power supply control unit 5 for the image data generation unit 7 and the backlight.

  In the user interface unit 9, two types of modes, for example, a wide viewing angle mode and a narrow viewing angle mode are set.

  When the requested viewing angle information (in this case, information indicating which of the wide viewing angle mode and the narrow viewing angle mode is selected) is input to the user interface unit 9, the control unit 10 stores the information in the image data generation unit 7 and the back view. This is transmitted to the power supply control unit 5 for writing.

  Based on the required viewing angle information from the control unit 10, the backlight power supply control unit 5 controls the backlight power supply 4 to increase the luminance of the backlight 3 as the required viewing angle is wider (or narrower). Let (or lower) change.

  More specifically, the backlight power supply control unit 5 turns off the backlight power supply 4 when the requested viewing angle information from the control unit 10 is the requested viewing angle information indicating that the narrow viewing angle mode is selected. By controlling, the current amount to the backlight 3 is reduced to a current amount lower than a normal current amount (current amount in the wide viewing angle mode) to change the luminance of the backlight 3 to be low. If the requested viewing angle information is the requested viewing angle information indicating that the wide viewing angle mode is selected, the backlight power supply 4 is controlled to change the current amount to the backlight 3 to the normal current amount. Thus, the luminance of the backlight 3 is changed to a high level (normal height).

  Here, the brightness of the backlight 3 in the narrow viewing angle mode is such that the display image G can be recognized by the user positioned in front of the liquid crystal panel 2 and the display image can be displayed from the third party positioned next to the user. The brightness of G is difficult to recognize, and the brightness of the backlight 3 in the wide viewing angle mode is such that the display image G can be recognized by both the user and the third party.

  More specifically, the distance between the liquid crystal panel 2 and the user located in front of the liquid crystal panel 2 (viewing angle 0 °) is 30 cm, and the distance between the user and a third person located next to the user is the adult's distance. If the average shoulder width is 40-45 cm, the viewing angle when a third person looks at the liquid crystal panel 2 is about 55 °. Therefore, the brightness of the backlight 3 in the narrow viewing angle mode is the brightness that the visibility from the viewing angle of about 55 ° is the worst while ensuring the visibility from the front (viewing angle 0 °), and the wide viewing angle mode. The luminance of the backlight 3 at that time is a luminance that can ensure visibility from the front (viewing angle 0 °) and visibility from a viewing angle of about 55 °.

Quantitatively speaking, for example, in order for the object part G1 on the display image G to be generally recognized, the luminance difference between the background part G2 and the object part G1 only needs to be about 10 cd / m ² or more. In the mode, the luminance of the backlight 3 may be changed so that the luminance difference between the background portion G2 and the object portion G1 is lower than about 10 cd / m ^{2. In} the wide viewing angle mode, the luminance of the backlight 3 is What is necessary is just to change so that the brightness | luminance difference of the background part G2 and the object part G1 may become about 10 cd / m < ² > or more.

  The color information holding unit 6 holds the color information of the respective parts G1, G2, and G3 of the display image G, but particularly for an object part (an object part that is not desired to be viewed by a third party) G1, required viewing angle information. The color information is held so as to have a plurality of gradations according to the color.

  For example, when the background part G2 of the display image G is set to white (corresponding to the maximum gradation in FIGS. 2 and 3) and the object part G1 is set to gray, the color of the object part G1 is wide. As the gradation in the viewing angle mode, for example, black (minimum gradation) is maintained so that the luminance difference from the color (white) of the background portion G2 increases, and the background portion G2 is used as the gradation in the narrow viewing angle mode. For example, a gray color (intermediate gradation) is maintained so that the luminance difference from the color (white) decreases. For the color of the portion G3 that may be visually recognized by a third party, for example, black (a color in which the luminance difference from the color of the background portion G2 increases) is maintained regardless of the narrow viewing angle mode and the wide viewing angle mode. Yes.

  The image data generation unit 7 determines the colors and background portions of the object portions G1 and G3 of the display image G based on the color information held in the color information holding unit 69 in accordance with the requested viewing angle information from the control unit 10. The display image G is generated by determining the color of G2, and the display image G is displayed on the liquid crystal panel 2 via the image data transmission unit 8.

  Next, the operation of the liquid crystal display device 1 will be described. Here, as described above, in the display image G, the background part G2 is set to white, the object part G1 that is not desired to be viewed by a third party is set to gray, and the object part that may be viewed by a third party A case where G2 is set to black will be described.

  When requested viewing angle information is input to the user interface unit 9, the requested viewing angle information is transmitted to the backlight power source control unit 5 and the image data generation unit 7 via the control unit 10.

  If the requested viewing angle information is the requested viewing angle information indicating that the narrow viewing angle mode is selected, the image data generating unit 7 performs the narrow viewing angle mode held in the color information holding unit 6. A display image G is generated based on the color information. That is, the background portion G2 is, for example, white, and for the object portion G1 that the third party does not want to see, the gradation of the color is the luminance of the gradation and the luminance of the background portion G2 (white). For example, the object portion G3 which is changed to a gray color (intermediate gradation) so that the difference is reduced (the visibility of the object portion G1 is narrowed to a narrow viewing angle) and may be visually recognized by a third party. For example, the display image G is generated in black, and the display image G is displayed on the liquid crystal panel 2 via the image data transmission unit 8.

In parallel with this, the backlight power source control unit 5 controls the backlight power source 4 to reduce the amount of current to the backlight 3 to a current amount lower than the normal current amount. Is changed so that the luminance difference between the object portion G1 and the background portion G2 is lower than, for example, about 10 cd / m ² (this further narrows the viewing angle of the object portion G1).

  In this way, the viewing angle of the object portion G1 (that is, the viewing angle of the display image G) is narrowed and the display image G is displayed on the liquid crystal panel 2.

  On the other hand, when the requested viewing angle information is requested viewing angle information indicating that the wide viewing angle mode has been selected, the image data generating unit 7 is in the wide viewing angle mode held by the color information holding unit 6. A display image G is generated based on the color information. That is, the background portion G2 is, for example, white, and for the object portion G1 that the third party does not want to see, the gradation of the color is the luminance of the gradation and the luminance of the background portion G2 (white). For example, the object portion G3 that is changed to black (minimum gradation) so that the difference increases (this increases the visibility of the object portion G1 and wide viewing angle) and may be viewed by a third party is, for example, The display image G is generated in black, and the display image G is displayed on the liquid crystal panel 2 via the image data transmission unit 8.

In parallel with this, the backlight power supply control unit 5 controls the backlight power supply 4 to increase the amount of current to the backlight 3 to a normal amount of current. The luminance difference between the object portion G1 and the background portion G2 is changed to be, for example, about 10 cd / m ² or more (this further widens the visibility of the object portion G1 and the wide viewing angle).

  In this way, the viewing angle of the object portion G1 (that is, the viewing angle of the display image G) is widened, and the display image G is displayed on the liquid crystal panel 2.

  According to the liquid crystal display device 1 configured as described above, a part of the display image G displayed on the liquid crystal panel 2 according to the requested viewing angle input to the viewing angle information input unit 9 (visited by a third party). Change the color of the object portion (for example, a communication message such as a character) G1) (more specifically, the larger the required viewing angle, the part of the color of the display image G (here, the color gradation)). The brightness of the color (in this case, the brightness of the gradation) and the color brightness of the remainder of the display image G (for example, the background portion G2) are changed so that the viewing angle of the display image G is increased. Thus, a liquid crystal display device is obtained that can change the viewing angle without complicating the configuration of the liquid crystal panel 2, increasing the thickness, and increasing power consumption, and without adding many hardware resources. be able to.

  Further, since only a part of the display image G (object portion G1) is changed in the wide viewing angle mode and the narrow viewing angle mode, the color of the entire display image G is changed as in the prior art. This has the advantage of using less memory. That is, when converting the color of the entire display image G as in the prior art, it is necessary to have a look-up table having output color data corresponding to all input color data (that is, a look-up table having a large capacity). A large-capacity memory is required. However, when only a part of the color of the display image G is changed as in the present invention, it is necessary to have such a large-capacity look-up table, so a large-capacity memory is required. There are advantages to not.

  Further, since only a part of the color of the display image G is changed, the color of the display image G can be changed in a short time (that is, the display image G can be compared with the case where the color of the entire display image G is changed as in the prior art. The viewing angle can be changed).

  In addition, as the required viewing angle input to the viewing angle information input unit is wider or narrower, the luminance of the backlight 3 is changed to be higher or lower, so that the viewing angle of the display image G is effectively widened or narrowed. Can be a corner. In particular, by reducing the luminance of the backlight 3 when the required viewing angle is narrow, it is possible to contribute to a reduction in power consumption of the backlight 3.

  In addition, the viewing angle information input section has two types, a wide viewing angle mode and a narrow viewing angle mode, so you can choose between a wide viewing angle and a narrow viewing angle. Can be improved.

  In addition, the viewing angle of the display image G can be changed only by changing the color gradation of the object portion G1 (for example, characters) displayed in a single color in the display image G (that is, only by setting a small amount of color information).

  Further, as in the present embodiment, the object portion (a part of the display image G) G1 is set to gray, and the background portion (the remaining portion of the display image G) G2 is white (the maximum gradation 63 in FIGS. 2 and 3). In the wide viewing angle mode, the color gradation of the object part G1 is changed to black (minimum gradation), and in the narrow viewing angle mode, the color gradation of the object part G1 is set. By changing to a gray color (intermediate gradation), the viewing angle of the display image G can be easily selectively changed to a wide viewing angle or a narrow viewing angle.

  Further, in this embodiment, when there is a frame portion G4 of the display image G as shown in FIG. 5, the color of the frame portion G4 is black in both the wide viewing angle mode and the narrow viewing angle mode (that is, the background). You may set to the color which the brightness | luminance difference with the color (white) of the part G2 becomes the largest. In this way, in the narrow viewing angle mode, the contrast of the eye follows the color of the frame portion G4, and an illusion can be made so that the gray object portion G1 becomes more difficult to visually recognize ( That is, the display image G can contribute to a narrow viewing angle.)

  Further, in this embodiment, the object portion G1 that changes the color gradation according to the viewing angle is a single color for convenience of explanation, but it may naturally be a multicolor.

  Further, in this embodiment, the user interface unit 9 has a format in which the wide viewing angle mode or the narrow viewing angle mode is selectively input by the user, but continuous viewing angle information is input. Correspondingly, the color gradation of the object portion G1 may be continuously changed, and the viewing angle of the display image G may be continuously changed.

It is a figure which shows the relationship between the viewing angle and the brightness | luminance in the liquid crystal panel in which a general gradation display is possible. It is a figure which shows the relationship between the gradation and the brightness | luminance in the liquid crystal panel in which a general gradation display is possible. It is a figure which shows the relationship between the viewing angle and the brightness | luminance in the liquid crystal panel in which a general gradation display is possible. 1 is a schematic configuration diagram of a liquid crystal display device according to an embodiment of the present invention. It is a figure which shows an example of the display image of the liquid crystal display device which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device, 2 Liquid crystal panel, 3 Backlight, 5 Power supply control part for backlight (backlight control means), 6 color information holding part, 7 Image data generation part (viewing angle change means), 8 Image data transmission part , 9 User interface part, 10 control part, G display image, G1 object part, G2 background part.

Claims (7)

A liquid crystal panel capable of gradation display;
A viewing angle information input unit for inputting information of a required viewing angle;
Viewing angle changing means for changing the viewing angle of the display image by changing the color of a part of the display image displayed on the liquid crystal panel according to the requested viewing angle input to the viewing angle information input unit;
A liquid crystal display device comprising: The viewing angle changing means is
As the required viewing angle is wider, the color of a part of the display image displayed on the liquid crystal panel is changed so that the difference between the luminance of the color and the luminance of the remaining color of the display image is increased, The liquid crystal display device according to claim 1, wherein the viewing angle of the display image is changed. A backlight for illuminating the liquid crystal panel;
Backlight control means for changing the brightness of the backlight higher as the required viewing angle input to the viewing angle information input unit is wider,
The liquid crystal display device according to claim 1, further comprising:   The liquid crystal display device according to claim 1, wherein the viewing angle information input unit is set with two types of modes, a wide viewing angle mode and a narrow viewing angle mode.   The liquid crystal display device according to claim 1, wherein the part of the display image is an object portion displayed in a single color.   The liquid crystal display device according to claim 5, wherein the part of the display image is a character. When the part of the display image is a gray object part and the remaining part of the display image is a white background part, the gradation of the part color is changed to black in the wide viewing angle mode. 5. The liquid crystal display device according to claim 4, wherein the gradation of the partial color is changed to a gray color in the narrow viewing angle mode.

Images