JP2008275855A - Display control method of liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display control method of a liquid crystal display device by which a viewing angle is widened and narrowed using viewing angle dependency of characteristics in a liquid crystal display panel. <P>SOLUTION: Each gradation level is actualized by average luminance of two gradation levels (n1, n2). A curve of (wide viewing angle processing) is selected so that the average luminance gradually increases when the gradation level gradually increases in a wide range of the gradation level. A curve of (narrow viewing angle processing) is selected so that inclination (inclination of tangent) becomes small in the wide range of the luminance level. In addition, when the curve is set so as to perform the narrow viewing angle processing, combination of (n1', n2') for actualizing luminance on the curve of the (narrow viewing angle processing) by the average luminance is selected when display data of a screen is created. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a display control method for a liquid crystal display device and a liquid crystal display device using the display control method, and more particularly to a display control method for a liquid crystal display device that performs display control using the viewing angle dependency of γ characteristics.

  In a liquid crystal display device, a TN liquid crystal display panel using a TN (Twisted Nematic) mode liquid crystal is widely used.

  However, the TN liquid crystal display panel has a problem that when a viewer visually recognizes the display surface from an oblique direction, the contrast ratio of the display is lowered and the viewer is visually recognized. That is, when an image in which a gradation difference is clearly identified when viewed from the front is viewed from an oblique direction, the luminance difference between gradations becomes unclear. In addition, the gradation characteristics are reversed, and when a portion that is visually recognized dark from the front is viewed from an oblique direction, a phenomenon that it is viewed brightly may occur (for example, see Patent Documents 1 and 2).

  As liquid crystal display panels with improved viewing angle characteristics, there are liquid crystal display panels in an IPS (In-Plane Switching) mode and an MVA (Multi-Domain Vertical Alignment) mode. In these liquid crystal display panels, a decrease in contrast ratio and a reversal of gradation characteristics when the display surface is viewed from an oblique direction are alleviated.

JP 2004-62146 A (paragraphs 0004-0006) JP-A-10-319373 (paragraph 0002)

  In the IPS mode liquid crystal display panel and the MVA mode liquid crystal display panel, the decrease in contrast ratio and the reversal of gradation characteristics when viewed from an oblique direction are alleviated. There remains a problem of viewing angle characteristics (viewing angle dependency of γ characteristics) that the γ characteristics when the surface is viewed from the front and the γ characteristics when viewed from an oblique direction are different. The viewing angle dependency of the γ characteristic means that the visible brightness (relative brightness) changes with respect to the brightness when the display surface is viewed from the front when the viewing angle of the display surface is different in each gradation. It is. For example, a phenomenon occurs in which a portion whose display contents can be determined when the display surface is viewed from the front is visually recognized with high luminance when viewed from an oblique direction, and the display content cannot be determined.

  FIG. 14A is an explanatory diagram showing viewing angle characteristics of a general IPS mode liquid crystal display panel, and FIG. 14B is an explanatory diagram showing viewing angle characteristics of a general MVA mode liquid crystal display panel. is there. 14A and 14B, the horizontal axis indicates the gradation level, and the vertical axis indicates the relative luminance. Note that the liquid crystal display panel can display 256 gradations. The relative luminance is the luminance when the maximum displayable luminance is 1 and the minimum luminance is 0. The angles (0 °, 30 °, 45 °, and 60 °) described in FIGS. 14A and 14B are angles (viewing angles) in the viewing direction from the normal to the display surface, and from the normal The angle tilted to the left or right. Hereinafter, the case where the display surface is visually recognized along the normal to the display surface may be expressed as “view the display surface from the front”.

  As shown in FIG. 14A, in the liquid crystal display panel of the IPS mode, the luminance is almost the same even when the viewing angle changes at each gradation level. Further, as shown in FIG. 14B, in the MVA mode liquid crystal display panel, the luminance increases as the viewing angle increases. As shown in FIG. 14B, in the MVA mode liquid crystal display panel, the γ characteristic when the display surface is viewed from the front and the γ characteristic when viewed from the oblique direction are different.

  The problem of the viewing angle dependence of the γ characteristic exists not only in the MVA mode liquid crystal display panel but also in other types of liquid crystal display panels such as a TN liquid crystal display panel.

  Various proposals have been made to improve the viewing angle dependency of the γ characteristic (see, for example, Patent Document 1 above).

  In addition, a proposal for realizing a special display state using the viewing angle dependency in the TN liquid crystal display panel has been made (see, for example, Patent Document 2 above). For example, Patent Document 2 describes a liquid crystal display device that can widen or narrow a viewing angle. In Patent Document 2, widening the viewing angle means keeping the contrast ratio at a high value even when the angle in the viewing direction from the normal to the display surface increases. In addition, narrowing the viewing angle means that the contrast ratio is extremely lowered when the viewing angle becomes a certain degree or more.

  However, Patent Documents 1 and 2 describe that a special display state is realized by using the viewing angle dependency of the γ characteristic (the characteristic that the luminance to be viewed changes when the viewing angle is different in each gradation). Not. Patent Documents 1 and 2 only use the viewing angle dependence of the contrast ratio in a TN liquid crystal display panel.

  An object of the present invention is to provide a display control method for a liquid crystal display device that can widen or narrow a viewing angle by using the viewing angle dependency of γ characteristics in a liquid crystal display panel.

  In the following description, widening the viewing angle means that the gradation difference can be discriminated even when the angle in the viewing direction from the normal to the display surface increases. In addition, narrowing the viewing angle means that the gradation difference cannot be discriminated when the angle in the viewing direction from the normal to the display surface exceeds a certain level.

  First, the characteristics of the liquid crystal display panel, which is the basis of the display control method of the liquid crystal display device according to the present invention, will be described. FIG. 1A is an explanatory diagram illustrating an example of the viewing angle dependency of the luminance of each gradation level in the MVA mode liquid crystal display panel. In FIG. 1A, the horizontal axis is the inclination (viewing angle) from the normal to the display surface, and is the angle θ inclined to the left or right from the normal. The positive value of the angle θ corresponds to the rightward inclination, and the negative value of the angle θ corresponds to the leftward inclination. The vertical axis represents the luminance I (n, θ) with respect to I (255, 0) (the luminance of the image at the gradation level 255 when the display surface is viewed from the front), that is, the relative luminance [I (n, θ) / I. (255, 0)]. n represents a gradation level. FIG. 1B shows the luminance I (n, θ) with respect to the gradation level 255 (the highest luminance level) at various angles (viewing angles) θ of the respective gradation levels, that is, relative luminance (luminance ratio) [I. (N, θ) / I (255, θ)]. Hereinafter, the relative luminance is simply referred to as “luminance”.

  As shown in FIG. 1B, when the absolute value of the viewing angle is small (close to 0 °) at each gradation level, the luminance is viewed low, but when the absolute value of the viewing angle is large, the luminance is viewed high. . In addition, the angle range (field of view) in which the luminance is high and visually recognized is relatively wide. Hereinafter, the fact that the luminance is visually recognized as low (or high) is simply referred to as low (or high) luminance. Further, the difference in luminance regarding the two gradation levels when the absolute value of the viewing angle is small is different from the difference in luminance when the absolute value of the viewing angle is large. For example, in the example shown in FIG. 1B, the difference between the luminance at the gradation level 160 (about 0.4) and the luminance at the gradation level 64 (about 0.1) when the viewing angle θ is 0 ° is When the viewing angle θ is 30 ° compared to 0.3, the difference between the luminance at the gradation level 160 (about 0.6) and the luminance at the gradation level 64 (about 0.25) is 0.35. When the viewing angle θ is 50 °, the difference between the luminance at the gradation level 160 (about 0.9) and the luminance at the gradation level 64 (about 0.5) is 0.4.

  Focusing on the four gradation levels, when the viewing angle θ is 0 °, the average value A of the luminances of the two gradation levels is the same as the average value B of the luminances of the other two gradation levels. Even when the viewing angle is increased (at an oblique viewpoint), the average value A of the luminances of the two gradation levels is not the same as the average value B of the luminances of the other two gradation levels. For example, when the viewing angle θ is 0 °, the brightness of the gradation level 128 (corresponding to the average value of the gradation level 128 and the gradation level 128: 0.25) and the gradation level 160 The average value of the luminance (about 0.4) and the luminance of the gradation level 64 (about 0.1) is substantially equal, but when the viewing angle θ is 50 °, the luminance of the gradation level 128 (about 0.75). ) Is different from the average value (about 0.7) of the luminance at the gradation level 160 (about 0.9) and the luminance at the gradation level 64 (about 0.5). Hereinafter, the average value of the luminance of the two gradation levels is referred to as average luminance.

  FIG. 2 is an explanatory diagram for explaining that the average value A and the average value B are not the same at an oblique viewpoint. As shown in FIG. 2A, when the viewing angle θ is 0 °, the luminance of the gradation level 160 (corresponding to the average value A when the two gradation levels are both 160) is the gradation. Although it is the same as the average value B of the luminance at the level 0 and the luminance at the gradation level 224, the average value A is larger than the average value B when the viewing angle θ is 50 °. In FIG. 2A, the arrows indicate the difference between the average value A and the average value B when the viewing angle θ is 50 °. Note that the gradation levels 0, 160, and 224 illustrated in FIG. 2 are examples. In addition, “one gradation display” described in FIG. 2A corresponds to luminance display at gradation level 160, and “two gradation average display” corresponds to luminance at gradation level 0 and gradation level. This corresponds to an average luminance display with a luminance of 224.

  FIGS. 2B and 2C show the state of luminance that is visually recognized when the four adjacent regions in the liquid crystal display panel have the gradation level 160 or the gradation level (0 + 224) / 2. ing. (0 + 224) / 2 indicates that the luminance is the luminance of gradation level 0 and the average luminance of gradation level 224. Note that the luminance of the gradation level 0 and the average luminance of the gradation level 224 are realized by, for example, temporal averaging or spatial averaging of the gradation levels, as will be described later.

  FIG. 2B shows a state of luminance visually recognized when the viewing angle θ is 0 °, and FIG. 2C shows a state of luminance visually recognized when the viewing angle θ is 50 °. It is shown. As shown in FIG. 2B, the luminance difference is not visually recognized when the viewing angle θ is 0 °. However, when the viewing angle θ is 50 °, the luminance difference is not visible as shown in FIG. Visible.

  According to the display control method of the liquid crystal display device according to the present invention, even when the average value A and the average value B are substantially the same when the display screen is observed from the front as described above, Special display is realized by utilizing the fact that the average value B is not the same.

The relationship between the gradation level n and the luminance I is the γ characteristic represented by the equation (1).
I (n, γ) = (n / 255) ^ γ (1)

  However, it is preferable to follow the inherent γ characteristic of the liquid crystal display panel. In the equation (1), I (n, γ) is the luminance at the gradation level n, and γ is generally 2.2. “^” Indicates a power exponent. The luminance I (n, γ) is the luminance when the viewing angle θ is 0 °.

  By selecting n1 and n2 satisfying the expression (2) for the luminance I (n, γ) when the gradation level is n, the gradation level n1 when the viewing angle θ is 0 °. The average luminance at the gradation level n2 is equal to the luminance at the gradation level n.

  I (n, γ) = [I (n1, γ) + I (n2, γ)] / 2 (2)

  As described above, even when the expression (2) is satisfied when the viewing angle θ is 0 °, when the MVA mode liquid crystal display panel is used, the average value A (two gray levels are Both are equivalent to the average value when n) and the average value B (corresponding to the average value of the luminance at the gradation level n1 and the luminance at the gradation level n2) are not the same. Therefore, the viewing angle is 0 ° between the case where the liquid crystal display panel performs display at gradation level n and the case where the luminance of the average value of gradation level n1 and gradation level n2 is displayed. The brightness that is visible when it becomes larger is not the same.

  FIG. 3 is an explanatory diagram showing a set of gradation levels n1 and n2 having the same average luminance when the viewing angle is 0 ° and different average luminance at an oblique viewpoint. As shown in the explanatory diagram of FIG. 3, there are many combinations of n1 and n2 that satisfy the expression (2) for the gradation level n. In FIG. 3, the arc indicated by the number with S indicates the position where the combination of (n1, n2) with respect to the gradation level indicated by the number exists. That is, the combination of (n1, n2) exists on the arc. Specifically, the set Sn of (n1, n2) that satisfies the expression (3) is a combination of (n1, n2) existing on the arc in FIG.

  Sn = {n1, n2 | I (n, γ) = [I (n1, γ) + I (n2, γ)] / 2} (3)

  Equation (3) shows all the combinations of (n1, n2) that satisfy the condition on the right side of |. In addition, since n is a discrete value (for example, any integer of 0 to 255), it is preferable that the set Sn has a sufficient condition as shown in, for example, the equation (4).

  Sn = {n1, n2 | I (n−0.5, γ) <[I (n1, γ) + I (n2, γ)] / 2 <I (n + 0.5, γ)} (4)

  When the viewing angle increases with respect to 0 °, the luminance (average value of luminance, that is, average luminance) by each of the combinations of a number of (n1, n2) belonging to the set Sn is different from the luminance at the gradation level n. Above, different from each other. This is because the brightness of each gradation level at a certain viewing angle is different as shown in FIG.

  Based on the characteristics shown in FIG. 1A, it is possible to derive the luminances of the gradation levels n1 and n2 when the viewing angle increases with respect to 0 °. Therefore, the average luminance of the gradation levels n1 and n2 can be derived. As an example, FIG. 4 shows the average luminance of each (n1, n2) combination belonging to the set Sn with respect to the gradation level n when the viewing angle is 60 °. In FIG. 4, the horizontal axis indicates the gradation level n, and the vertical axis indicates the luminance. FIG. 4 also shows a curve indicating the luminance when the viewing angle θ is 0 ° when γ = 2.2.

  In FIG. 4, a hatched area indicates a luminance area that can be selected when the viewing angle is 60 ° when the average luminance is the same when the viewing angle is 0 °. In FIG. 4, the curve shown as (lower limit) shows the lowest value among the average luminances of the combinations of (n1, n2) for the respective gradation levels n (n = 0 to 255). The curve shown as (upper limit) shows the highest value among the average luminances of the combinations of (n1, n2) for the respective gradation levels n (n = 0 to 255). Note that (normally n display) indicates the luminance of the gradation level n when the viewing angle is 60 °. In FIG. 4, (usually n display) matches (upper limit). However, in general, (usually n display) and (upper limit) do not match.

  For example, when the gradation level n is 100, the (lower limit) is about 0.5, and the (upper limit) is the same as in the case of (usually n display), which is almost 0.8. This means that when two combinations of (n1, n2) having the same average luminance are selected when the viewing angle is 0 °, 0.4 (= 0) when the viewing angle is 60 °. .8-0, 4) indicates that a difference can be made in the luminance to be visually recognized.

  When the viewing angle is 0 °, a curve (characteristic) indicating (usually n display) matches a curve indicating (lower limit) and a curve indicating (upper limit).

  Not only when the gradation level n is 100, but also for other gradation levels n, similarly, two (n1, n2) combinations having the same average luminance when the viewing angle is 0 ° are used. When selected, if the viewing angle is 60 °, it is possible to make a difference in the visually recognized luminance. That is, FIG. 4 illustrates the case where the viewing angle is 60 °, but the shape of the region within the hatched line is different at other viewing angles, but the region similar to the shaded region in FIG. is there.

  FIG. 5 shows the luminance of the combination of (n1, n2) and (n1 ′, n2 ′) that satisfies the expression (2) when the viewing angle θ is 0 °, and the luminance of the gradation level n. It is explanatory drawing which shows the example of the brightness | luminance in an oblique viewpoint. As an example, the gradation level n is 186. The gray level n1 is 80, the gray level n2 is 246, the gray level n1 'is 0, and the gray level n2' is 255. 5A shows two pixels at gradation level n, FIG. 5B shows a pixel at gradation level n1 and a pixel at gradation level n2, and FIG. 5C shows a gradation level n2. A pixel of level n1 ′ and a pixel of gradation level n2 ′ are shown. In FIG. 5, the difference in the density of the hatched lines indicates that the luminance is different.

  Note that the combination of (n1, n2) and the combination of (n1 ′, n2 ′) are combinations existing on the same arc in FIG. At an oblique viewpoint, the luminance at the gradation level n, the average luminance at the gradation levels n1 and n2, and the average luminance at the gradation levels n1 'and n2' are different from each other.

  The display control method of the liquid crystal display device according to the first aspect of the present invention is a liquid crystal display panel in which the γ characteristic when the display surface as described above is viewed from the front and the γ characteristic when viewed from the oblique direction are different. Is a display control method for a liquid crystal display device using the above, and for each gradation level n (n: natural number), the average luminance when the display surface is viewed from the front is substantially the same (the extent that the viewer sees the same luminance) The difference in average brightness when viewed from an oblique direction (for example, the angle of the viewing direction from the normal to the display surface is 60 °) is different (N: positive number of 2 or more). (Integer) combination of gradation levels, when the gradation level gradually increases between the lowest gradation level and the highest gradation level (between the lowest level and the highest level actually used for display) Average brightness gradually increases A combination of gradation levels to be selected is selected, and an image by average display of the selected combinations of N gradation levels is displayed on the liquid crystal display panel. By controlling as such, wide viewing angle display is realized.

  In the display control method of the liquid crystal display device according to the second aspect of the present invention, the average luminance when the display surface is viewed from the front is substantially the same for each gradation level n (n: natural number) and viewed from an oblique direction. A combination of N (N: a positive integer greater than or equal to 2) gradation levels having different average luminances, and in a predetermined section between the lowest gradation level and the highest gradation level, the gradation level A combination of gradation levels in which the average luminance does not substantially change even if the brightness changes is selected, and an image by average display of the selected combinations of N gradation levels is displayed on the liquid crystal display panel. By controlling in such a manner, a narrow viewing angle display is realized.

  In the display control method of the liquid crystal display device according to the third aspect of the present invention, the average luminance when the display surface is viewed from the front is substantially the same for each gradation level n (n: natural number) and viewed from an oblique direction. The average brightness gradually increases as the gradation level gradually increases between the lowest gradation level and the highest gradation level, which are gradation levels n1, n2 (n1, n2: natural numbers) with different average luminance. The gradation levels n1 and n2 are selected, and an image by the average display of the selected gradation levels n1 and n2 is displayed on the liquid crystal display panel. By controlling as such, wide viewing angle display is realized.

  A display control method for a liquid crystal display device according to a fourth aspect of the present invention is a liquid crystal display device using a liquid crystal display panel having different γ characteristics when the display surface is viewed from the front and γ characteristics when viewed from an oblique direction. In the display control method, for each gradation level n (n: natural number), the average luminance when the display surface is viewed from the front is substantially the same, and the average luminance when viewed from an oblique direction is different. n1 ′, n2 ′ (n1 ′, n2 ′: natural numbers), and in a predetermined section between the lowest gradation level and the highest gradation level, the average luminance is substantially effective even if the gradation level changes. The gradation levels n1 ′ and n2 ′ that do not change to 1 are selected, and an image based on the average display of the selected gradation levels n1 ′ and n2 ′ is displayed on the liquid crystal display panel. By controlling in such a manner, a narrow viewing angle display is realized.

  An average display of gradation levels (N or (n1, n2)) is realized by, for example, a time average and / or a space average (a time average, a space average, or a combination of a time average and a space average).

  According to the present invention, the viewing angle can be widened or narrowed by utilizing the viewing angle dependency of the γ characteristic in the liquid crystal display panel.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In the present invention, as shown in FIG. 2A, the average value A of the luminances of the two gradation levels is the same as the average value B of the luminances of the other two gradation levels at the viewing angle of 0 °. However, when the viewing angle is increased (at an oblique viewpoint), the average value A of the luminances of the two gradation levels is not the same as the average value B of the luminances of the other two gradation levels. For example, the viewing angle is widened or the viewing angle is narrowed by utilizing the existence of a hatched region in FIG. That is, the slope of the γ curve (curve representing the γ characteristic) is changed so as to substantially widen the viewing angle or narrow the viewing angle. In this embodiment, it is assumed that an MVA mode liquid crystal display panel is used. However, if the liquid crystal display has a characteristic as shown in FIG. 2A, the liquid crystal display in a mode other than the MVA mode is used. Panels can be used.

  FIG. 6 is an explanatory diagram showing that the γ characteristic is different when the viewing angle is different in the MVA mode liquid crystal display panel (MVA Display). In FIG. 6, the horizontal axis indicates the gradation level n, and the vertical axis indicates the luminance. FIG. 6 shows the luminance of one gradation level n, not the average luminance of two gradation levels. FIG. 4 also shows a curve indicating the luminance when the viewing angle θ is 0 ° when γ = 2.2. As shown in FIG. 6, for example, the luminance in the γ characteristic at a viewing angle of 45 ° decreases with respect to the luminance in the γ characteristic at a viewing angle of 60 ° (see the arrow in FIG. 6). Further, the luminance in the γ characteristic at a viewing angle of 30 ° is further reduced.

  FIG. 4 shows the average luminance of each (n1, n2) combination belonging to the set Sn with respect to the gradation level n when the viewing angle is 60 °, and the hatched area has a viewing angle of 0 °. In some cases, when the average luminance is the same, it is a region of luminance that can be selected when the viewing angle is 60 °. For example, the maximum value of the average luminance by the combination of (n1, n2) that realizes the gradation level 100 is approximately 0.8. Further, the minimum value of the average luminance by the combination of (n1, n2) that realizes the gradation level 100 is approximately 0.5.

  FIG. 7 is an explanatory diagram showing a combination of (n1, n2) used in the display control method of the liquid crystal display device of the present embodiment. FIG. 7 shows the average luminance of the combination of (n1, n2) when the viewing angle is 60 °, as in the case of FIG. In FIG. 7, the horizontal axis indicates the gradation level n, and the vertical axis indicates the luminance.

  (Processing limit) in FIG. 7 is the same as (Lower limit) in FIG. Further, (usually 60 ° viewpoint) is the same as (usually n display) in FIG. 4, and indicates the luminance of the gradation level n when the viewing angle is 60 °.

  There is a combination of (n1, n2) selected when a wide viewing angle is desired on the curve shown as (wide viewing angle processing), and the viewing angle is narrowed on the curve shown as (narrow viewing angle processing). There are (n1, n2) combinations that are selected when desired.

  The curve of (wide viewing angle processing) is selected so that there is a change in luminance when the gradation level is different in a wide range of gradation levels within the hatched area shown in FIG. That is, the average luminance is selected so as to gradually increase as the gradation level gradually increases.

  The curve of (narrow viewing angle processing) is selected so that the inclination (tangential inclination) becomes small in a wide range of gradation levels within the hatched area shown in FIG. That is, the luminance change is selected to be small in the widest possible range even if the gradation level is different. In other words, in a predetermined section between the lowest gradation level and the highest gradation level, the average luminance is selected so as not to change substantially even if the gradation level changes.

  Since the combination of (n1, n2) on the (wide viewing angle processing) curve is selected so that there is always a change in luminance when the gradation level is different, observation is possible even when the viewing angle is 60 °. The difference in brightness is visually recognized by the person. That is, the observer can determine the display image. In general, as the viewing angle approaches 60 ° from 0 °, an observer can more easily recognize the difference in luminance. Also, the combination of (n1, n2) on the (narrow viewing angle processing) curve is selected so that the luminance change is small even if the gradation level is different, so that the viewing angle is 60 ° It is difficult for the observer to visually recognize the difference in luminance. That is, it is difficult for the observer to determine the display image.

  Then, even if the viewing angle is large, if the gradation level is varied so that there is a change in luminance in a wide range of gradation levels within the hatched region shown in FIG. If a curve with a non-zero inclination (for example, a substantially straight line with an inclination) is selected as a (wide viewing angle processing) curve in a wide range, the observer can discriminate the display image from 0 ° to at least the viewing angle. . That is, a wide viewing angle is obtained.

  Further, when the viewing angle is large, it is selected so that the inclination is small in a wide range of gradation levels in the shaded area shown in FIG. 4, that is, the inclination is close to 0 in the wide range of gradation levels. If a curve (for example, a substantially straight line with a slope of 0) is selected as the (narrow viewing angle processing) curve, the observer cannot discriminate the display image at least at a viewing angle near the viewing angle. Actually, it becomes impossible to determine the display image before the viewing angle is reached (at a viewing angle smaller than the viewing angle). That is, it becomes a narrow viewing angle.

  Hereinafter, the combination of gradation levels on the curve of (wide viewing angle processing) is (n1, n2), and the combination of gradation levels on the curve of (narrow viewing angle processing) is (n1 ′, n2 ′). And When it is set to perform wide viewing angle processing, a combination of (n1, n2) that realizes the luminance on the curve of (wide viewing angle processing) with average luminance when creating screen display data Select. Further, when the narrow viewing angle processing is set to be performed, the luminance on the curve of (narrow viewing angle processing) is realized by the average luminance when the screen display data is created (n1 ′, n2). ') Select a combination.

  As described above, in this embodiment, there are many combinations of (n1, n2) having the same average luminance when the viewing angle is 0 °, and when the viewing angle is increased, the average luminance of each of these combinations is different. This makes it possible to widen or narrow the field of view of the liquid crystal display panel.

  In this embodiment, it is assumed that monochrome display is performed on the liquid crystal display panel, but the γ characteristics of R (red), G (green), and B (blue) do not completely match. When performing display control for a color image, it is preferable to perform display control according to the present embodiment for each of R, G, and B γ characteristics.

  Specifically, since the RGB γ characteristics in the front view in RGB are different for each color, when selecting the combination of (n1, n2), that is, when selecting the elements of the set Sn, the color image in the front view In order to compensate for the appearance, it is preferable to consider the γ characteristics of R, G, and B. That is, a combination of (n1, n2) that satisfies the equation (4) is selected for each of R, G, and B. By selecting the elements of the set Sn in consideration of the γ characteristics of R, G, and B, the appearance of the color image in the front view can be greatly improved. In order to maximize the effect of viewing angle control, when selecting the combination (n1, n2) with the highest luminance and the combination (n1 ′, n2 ′) with the lowest luminance from the set Sn, R , G, and B are preferably considered.

  In this embodiment, the average luminance of two gradation levels (n1 or n1 'and n2 or n2') is used, but the average luminance of three or more gradation levels may be used.

  Hereinafter, examples for realizing the display control method of the liquid crystal display device of each of the above embodiments will be described.

  FIG. 8 is a block diagram showing an example of a liquid crystal display device together with an MPU (Micro Processing Unit) 40. In the example shown in FIG. 8, a liquid crystal display panel 10 in which TFTs (Thin Film Transistors) are arranged in a matrix and MVA mode liquid crystal is sandwiched between a pixel electrode and a common electrode is used. A drive circuit for driving the liquid crystal display panel 10 includes a source driver (data electrode driver) 12 to which each source electrode (source wiring) as a data electrode connected to the source of the TFT in the same column in the liquid crystal display panel 10 is connected, A gate driver (scanning electrode driver) 13 connected to each gate electrode (gate wiring) as a scanning electrode connected to the gate of the TFT in the same row in the liquid crystal display panel 10, and a voltage for generating a data voltage as a source driver 12 And a power supply circuit 14 for supplying a voltage for generating a selection voltage (ON voltage) and a non-selection voltage (OFF voltage) to the gate driver 13.

  The controller 11 as a control circuit has a RAM 111 for temporarily storing display data (pixel data) input from an MPU provided outside the drive circuit, and causes the source driver 12 and the gate driver 13 to start a frame. A VSYNC (vertical synchronization) signal corresponding to the indicated signal is output, and an LP (Latch Pulse) signal is output for each selection period (a period in which a selection voltage as an ON voltage is applied to one gate wiring). .

  The gate driver 13 has a built-in counter, and resets the counter when the VSYNC signal is input, and increments the counter value by +1 when the LP signal is input. Then, a selection voltage for making the TFT gate conductive is applied to the gate wiring indicated by the counter value, and a non-selection voltage for making the TFT gate shut off is applied to the other gate wiring. A common voltage output unit 131 built in the gate driver 13 applies a common voltage to the common wiring.

  When the LP signal is input, the source driver 12 latches the data signal and applies a data voltage corresponding to the latched data signal to the source wiring. Since the gate driver 13 applies the selection voltage to the gate wiring in synchronization with the LP signal, the source driver 12 applies the data voltage to each source wiring in synchronization with the application of the selection voltage to the gate wiring.

  When the MPU 40 is set to perform wide viewing angle processing, when creating display data of the screen, for example, the MPU 40 realizes the luminance on the curve of (wide viewing angle processing) in FIG. 7 with average luminance. A combination of (n1, n2) is selected. Note that the combination of (n1, n2) is selected for each gradation level. In practice, the combination of (n1, n2) for realizing the luminance on the curve of (wide viewing angle processing) with the average luminance is set in, for example, a ROM data table. The MPU 40 reads out a combination of (n1, n2) corresponding to the gradation level to be used from the data table.

  Further, when the MPU 40 is set to perform narrow viewing angle processing, when creating display data for the screen, for example, the luminance on the curve of (narrow viewing angle processing) in FIG. A combination of (n1 ′, n2 ′) to be realized is selected. Note that the combination of (n1 ', n2') is selected for each gradation level. In practice, a combination of (n1 ′, n2 ′) that realizes the luminance on the curve of (narrow viewing angle processing) with average luminance is set in, for example, a ROM data table. The MPU 40 reads a combination of (n1 ′, n2 ′) corresponding to the gradation level to be used from the data table.

  In addition, the MPU 40 transmits a normal original image, instructs whether to perform further wide viewing angle processing, narrow viewing angle processing, or display the original image, and the control circuit that receives the command (N1, n2) may be selected.

  Then, the generated display data, that is, data indicating the gradation level of each pixel is output to the liquid crystal display device. In the liquid crystal display device, the controller 11 temporarily stores display data in the RAM 111. The controller 11 outputs display data stored in the RAM 111 to the source driver 12.

  Next, a method for realizing average display for obtaining average luminance will be described. First, a method for realizing average luminance by time averaging will be described. FIG. 9 is an explanatory diagram for explaining a method for realizing the average luminance by two gradation levels. Each square in FIGS. 9A and 9B represents a pixel. In FIGS. 9A and 9B, pixels having the same small letter alphabet a to p represent the same pixel. The number “1” in the pixel indicates the display in the first frame, and the number “2” indicates the display in the second frame. Further, it is assumed that the gradation level of the pixel assigned the number “2” is higher than the gradation level of the pixel assigned the number “1”. For example, the gradation level of the pixel indicated by a2 is higher than the gradation level of the pixel indicated by a1. 9 indicates that the luminance in the first frame is different from the luminance in the second frame.

  When the display shown in FIG. 9 (A) and the display shown in FIG. 9 (B) are alternately displayed for each frame, the luminance depending on the gradation level of the pixel to which the number “1” is attached and “2” are displayed. The average luminance of the luminance according to the gradation level of the pixel to which the number is attached is visually recognized. Therefore, each pixel indicated by the uppercase alphabet in FIG. 9C is represented by the luminance according to the gradation level of the lowercase alphabetic pixel to which the number “1” is attached and the alphabet to which the number “1” is attached. It is visually recognized by the average luminance with the luminance according to the gradation level of the pixel to which the numeral “2” is attached in the same alphabet.

  Therefore, the capital letters A to P indicate natural numbers representing arbitrary gradation levels 0 to 255 of the pixels, respectively. Further, (a1 to p1, a2 to p2) corresponds to the above (n1, n2). For example, (a1, a2) represents two gradation levels that are selected to display the gradation level A on average. In detail, it has the relationship which satisfy | fills the following formula | equation.

  I (A, γ) = [I (a1, γ) + I (a2, γ)] / 2 (a1 ≦ a2)

  In the example shown in FIG. 9, the gradation levels of the pixels A to P are different. Accordingly, display in which 16 types of average luminance are visually recognized is realized. When realizing an average luminance of a certain gradation level n, for example, the gradation level of the pixel a1 shown in FIG. 9 corresponds to the above n1 or n1 ′, and the gradation level of the pixel a2 corresponds to the above n2 or n2 ′. Correspond. The MPU 40 can realize the average luminance of the two gradation levels by the method as shown in FIG.

  Even when the average luminance of three or more gradation levels is used, display is performed at each gradation level in consecutive frames according to the number of gradation levels at which the luminance is averaged. FIG. 10 is an explanatory diagram for explaining a method for realizing an average luminance with four gradation levels. Each square in FIGS. 10A to 10D represents a pixel. 10A to 10D, pixels having the same small letter alphabets a to p represent the same pixel. A number in a pixel indicates a display in a frame indicated by the number. In each pixel, the gradation levels in different frames are different. For example, (the gradation level of the pixel indicated by a1) ≦ (the gradation level of the pixel indicated by a2) ≦ (the gradation level of the pixel indicated by a3) ≦ (the gradation level of the pixel indicated by a4) is there.

Therefore, a combination that satisfies the following formula is selected.
I (A, γ) = [I (a1, γ) + I (a2, γ) + I (a3, γ) + I (a4, γ)] / 4 (a1 ≦ a2 ≦ a3 ≦ a4)

  When the display shown in FIG. 10 (A) to the display shown in FIG. 10 (D) are displayed in order, the luminance according to the gradation level of the pixel to which the number “1” is attached and the number “2” are attached. The average luminance of the luminance depending on the gradation level of the pixel, the luminance depending on the gradation level of the pixel assigned with the numeral “3”, and the luminance depending on the gradation level of the pixel assigned with the numeral “4” Is visible.

  In the example shown in FIG. 10, the gradation levels of 16 pixels are different. Accordingly, display in which 16 types of average luminance are visually recognized is realized. However, for example, when the average luminance of a certain gradation level n is realized by the average value of the luminances of the gradation levels n1, n2, n3, and n4, the gradation level of the pixel a1 corresponds to n1, and the level of the pixel a2 The tone level corresponds to n2, the tone level of the pixel a3 corresponds to n3, and the tone level of the pixel a4 corresponds to n4. Further, the MPU 40 can realize the average luminance by the method as shown in FIG.

  Next, a method for realizing average luminance by spatial averaging will be described. FIG. 11 is an explanatory diagram for explaining a method for realizing the average luminance by two gradation levels. Each square in FIGS. 11A and 11B represents a pixel. Each pixel indicated by uppercase alphabets A to P in FIG. 11A is the same pixel as each pixel indicated by lowercase alphabets a to p in FIG.

  Assume that 16 pixels shown in FIG. 11A are pixels of an image (original image) to be displayed. The MPU 40 lowers the gradation level of the image to be displayed on the pixels (a1, c1, f1, h1, i1, k1, n1, p1) numbered “1” in FIG. This is realized by assigning a tone level and assigning a higher tone level to the pixels (b2, d2, e2, g2, j2, l2, m2, o2) to which the number “2” is attached. The pixels with the number “1” and the pixels with the number “2” are arranged alternately in space.

  Note that the gradation levels (all gradation levels are the same) of the pixels a1 to p1 to which the number “1” is attached correspond to the above n1 or n1 ′, and the pixels b2 to b2 to which the number “2” is attached. The gradation level of o2 (the gradation levels are all the same) corresponds to the above n2 or n2 ′. Further, the MPU 40 can realize the average luminance by the method as shown in FIG.

  FIG. 12 is an explanatory diagram for explaining a method for realizing the average luminance by four gradation levels. Each square in FIG. 12 represents a pixel. The MPU 40 assigns the gradation level of the image to be displayed to the pixels a1, c1, i1, k1 with the number “1” in FIG. 12, and assigns the number “2” to the pixel. The second lowest gradation level is assigned to the pixels f2, h2, n2, and p2, and the second highest gradation level is assigned to the pixels e3, g3, m3, and o3 that are numbered “3”. This is realized by assigning the lowest gradation level to the pixels b4, d4, j4 and l4 to which the numeral “4” is attached. Arbitrary adjacent four pixels are a pixel with a number “1”, a pixel with a number “2”, a pixel with a number “3”, and a number “4”. It consists of attached pixels. That is, pixels with the same number are spatially distributed.

  In the case where one average luminance is realized by an average luminance value based on the gradation levels of n1, n2, n3, and n4, for example, the gradation levels of the pixels a1, c1, i1, and k1 correspond to n1, and the pixel f2 , H2, n2, and p2 correspond to n2, the gradation levels of pixels e3, g3, m3, and o3 correspond to n3, and the gradation levels of pixels b4, d4, j4, and l4 correspond to n4. To do. Further, the MPU 40 can realize the average luminance by the method as shown in FIG.

  As described above, the average luminance is realized by the time average or the space average, but the time average and the space average may be used in combination.

  FIG. 13 is an explanatory diagram showing a specific method of selecting (n1, n2) (or (n1 ′, n2 ′)) when the gradation level n is 0 to 255. Here, the case where it is set to perform wide viewing angle processing is taken as an example. The MPU 40 is configured to be able to read data from a ROM in which the data table shown in FIG. 13B is stored. In the data table shown in FIG. 13B, the combination of (n1, n2) corresponding to each gradation level from 0 to 255, and the gradation level n is set when the viewing angle is 0 °. Although it is visually recognized, the combination data of (n1, n2) that is visually recognized at a luminance different from the luminance of the gradation level n is set at an oblique viewpoint. Each of the data (n1, n2) shown in FIG. 13B is data that realizes the luminance on the curve of (wide viewing angle processing) in FIG. 7 at each gradation level n.

  This is a data table similar to the data table shown in FIG. 13B, in which data of a combination of (n1 ′, n2 ′) used when narrow viewing angle processing is set is set. A data table is also stored in the ROM in advance. Each (n1 ′, n2 ′) data in the data table is data for realizing the luminance on the curve of (narrow viewing angle processing) in FIG. 7 at each gradation level n.

  In actuality, as shown in FIG. 13A, the MPU 40 includes, as an example of spatial averaging, a pixel to which n1 (or n1 ′) is assigned and a pixel to which n2 (or n2 ′) is assigned on the display screen. Decide in advance. The pixels to which n1 (or n1 ') is assigned and the pixels to which n2 (or n2') is assigned are alternately arranged. Then, (n1, n2) (or (n1 ′, n2 ′)) corresponding to the gradation level n of each pixel is used for the data table (or narrow viewing angle processing) shown in FIG. Data table).

  Note that when display control of average luminance is performed for each of R, G, and B, as shown in FIG. 13C, each of R, G, and B is virtually regarded as one pixel. Thus, the higher gradation level n1 (or n1 ′) and the lower gradation level n2 (or n2 ′) of (n1, n2) (or (n1 ′, n2 ′)) may be arranged. preferable.

  Further, in the above-described embodiments and examples, when the wide viewing angle processing is set to be performed, the wide viewing angle processing prepared in advance is used when any display image is displayed. If (n1, n2) is selected from the data table (see FIG. 13B) and the narrow viewing angle processing is set, any display image can be displayed. (N1 ′, n2 ′) is selected from a data table for narrow viewing angle processing prepared in advance. In other words, the γ curve to be applied is one type regardless of the content of the display image. However, the γ curve to be applied may be changed according to the content of the display image. For example, in the case of a dark image as a whole, it is preferable to use the original γ curve (curve of γ = 2.2) without using the data table.

  The present invention is applicable to a liquid crystal display device using a liquid crystal display panel in which a γ characteristic when a display surface such as an MVA mode is viewed from the front and a γ characteristic when viewed from an oblique direction are different.

Explanatory drawing which shows an example of the viewing angle dependence of the brightness | luminance of each gradation level in the liquid crystal display panel of a MVA mode. Explanatory drawing for demonstrating that the average value A and the average value B do not become the same at an oblique viewpoint. Explanatory drawing which shows set Sn of gradation level n1, n2 from which an average brightness | luminance is the same when a viewing angle is 0 degree, and an average viewpoint differs in an oblique viewpoint. Explanatory drawing which shows the average brightness | luminance of each (n1, n2) combination which belongs to set Sn. Explanatory drawing which shows the example of the brightness | luminance by two gradation levels in which the brightness | luminance of gradation level n and an average brightness | luminance are comparable when viewing angle (theta) is 0 degree. Explanatory drawing which shows that (gamma) characteristics differ if a viewing angle differs in the liquid crystal display panel of a MVA mode. Explanatory drawing which shows the combination of (n1, n2) used in the display control method of a liquid crystal display device. The block diagram which shows an example of a liquid crystal display device with MPU. Explanatory drawing for demonstrating the method for implement | achieving the average brightness | luminance by two gradation levels by time average. Explanatory drawing for demonstrating the method for implement | achieving the average brightness | luminance by four gradation levels by time average. Explanatory drawing for demonstrating the method for implement | achieving the average brightness | luminance by two gradation levels by a spatial average. Explanatory drawing for demonstrating the method for implement | achieving the average brightness | luminance by four gradation levels by a spatial average. Explanatory drawing which shows the concrete selection method of (n1, n2) when the gradation level n is 0-255. Explanatory drawing which shows the viewing angle characteristic of the liquid crystal display panel of an IPS mode, and the liquid crystal display panel of an MVA mode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Liquid crystal display panel 11 Controller 12 Source driver 13 Gate driver 14 Power supply circuit 40 MPU
111 RAM
131 Common voltage output

Claims (5)

A display control method for a liquid crystal display device using a liquid crystal display panel having different γ characteristics when viewed from the front and γ characteristics when viewed from an oblique direction,
For each gradation level n (n: natural number), the average brightness when the display surface is viewed from the front is substantially the same, and the average brightness when viewed from an oblique direction is different (N: a positive integer of 2 or more) ) And a combination of gradation levels in which the average luminance gradually increases as the gradation level gradually increases between the lowest gradation level and the highest gradation level,
A display control method for a liquid crystal display device, characterized in that an image based on an average display of a combination of N selected gradation levels is displayed on a liquid crystal display panel. A display control method for a liquid crystal display device using a liquid crystal display panel having different γ characteristics when viewed from the front and γ characteristics when viewed from an oblique direction,
For each gradation level n (n: natural number), the average brightness when the display surface is viewed from the front is substantially the same, and the average brightness when viewed from an oblique direction is different (N: a positive integer of 2 or more) ), And in a predetermined section between the lowest gradation level and the highest gradation level, the average luminance does not substantially change even if the gradation level changes. Select a combination
A display control method for a liquid crystal display device, comprising: displaying an image based on an average display of a combination of N selected gradation levels on a liquid crystal display panel. A display control method for a liquid crystal display device using a liquid crystal display panel having different γ characteristics when viewed from the front and γ characteristics when viewed from an oblique direction,
For each gradation level n (n: natural number), the average brightness when the display surface is viewed from the front is substantially the same, and the gradation levels n1, n2 (n1, n2: A natural number), and gradation levels n1 and n2 are selected such that the average luminance gradually increases as the gradation level gradually increases between the lowest gradation level and the highest gradation level;
A display control method for a liquid crystal display device, characterized in that an image based on an average display of selected gradation levels n1 and n2 is displayed on a liquid crystal display panel. A display control method for a liquid crystal display device using a liquid crystal display panel having different γ characteristics when viewed from the front and γ characteristics when viewed from an oblique direction,
For each gradation level n (n: natural number), the average luminance when the display surface is viewed from the front is substantially the same, and the gradation levels n1 ′ and n2 ′ (n1 ′) are different from each other when viewed from an oblique direction. , N2 ′: natural number) and in a predetermined section between the lowest gradation level and the highest gradation level, the gradation level n1 ′ where the average luminance does not substantially change even if the gradation level changes. , N2 ′,
A display control method for a liquid crystal display device, comprising: displaying an image based on an average display of selected gradation levels n1 ′ and n2 ′ on a liquid crystal display panel. The display control method for a liquid crystal display device according to any one of claims 1 to 4, wherein the average display of the two gradation levels is realized by a time average and / or a spatial average of the two gradation levels. .

Images