JP2011227424A - Liquid crystal display - Google Patents

Abstract

An object of the present invention is to provide a liquid crystal display device capable of obtaining an optimum gradation-luminance characteristic in a viewing direction regardless of ambient illuminance conditions.
A liquid crystal display device according to the present invention includes a display region 7 for displaying an image and a peripheral portion thereof, and a light detection pixel 9 that is disposed in the peripheral portion and has the same configuration as the pixels disposed in the display region 7. Based on the illuminance sensor 11 that is disposed in the peripheral portion with a predetermined positional relationship with the light detection pixel 9 and detects light incident from the light detection pixel 9, and the illuminance value detected by the illuminance sensor 11, And a conversion circuit 17 for converting the gradation-luminance characteristics of the display image in the display area 7.
[Selection] Figure 2

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device that is visible in an environment where ambient light changes.

  When viewing the display image of a liquid crystal display (LCD) in an environment where ambient light exists, when the brightness of the display image is constant, the visibility of the display image is very bright The display image feels dark, and when the surroundings are dark, the display image feels dazzling (bright). In either case, the visibility is poor. Therefore, in order to obtain good visibility, the brightness of the surrounding environment (ambient illuminance) is detected by an illuminance sensor. When the ambient illuminance is high, the brightness of the backlight is increased, and when the ambient illuminance is low A technique for reducing the brightness of the backlight is applied.

  However, there is a limit to obtaining good visibility by increasing the brightness of the backlight when the LCD is viewed in a very bright ambient environment such as in direct sunlight, and the power consumption is increased. There was a problem.

  As countermeasures against such problems, a transflective LCD in which a transmissive part and a reflective part are provided in each pixel of the LCD, or a so-called micro-reflective structure in which a transflective layer is provided between a transmissive liquid crystal panel and a backlight. An LCD having both reflection characteristics using ambient light and transmission characteristics using backlight light, such as a type LCD, is useful.

  As described above, the display image of the transflective LCD is displayed by light that combines the reflection component of ambient light and the transmission component of backlight light at a predetermined ratio, and when the ambient illuminance is low, the transmission component is displayed. Is mainly used, and when the ambient illuminance is high, the light mainly using the reflection component is used. However, when the ambient illuminance is high, the reflection component is mainly used, so that the intermediate gradation of the display image is bright (high brightness) and is visually recognized. Therefore, even the same display image is visually recognized as an image having different luminance depending on the ambient illuminance. Further, the above-described micro-reflection type LCD also has a different tendency from the semi-transmission type LCD, but the gradation-relative luminance characteristic changes depending on the ambient illuminance.

  Conventionally, the brightness of the surrounding environment is detected by an illuminance sensor, and the gradation voltage applied to the liquid crystal is changed according to the detected value, or the display image data is converted. Thus, a technique for controlling the gradation-luminance characteristics is disclosed (for example, see Patent Document 1).

JP 2008-40488 A

  Conventionally, the illuminance sensor detects the ambient illuminance and controls the gradation-luminance characteristics. However, the viewing angle characteristics of the reflection component of the transflective LCD are not uniform and have a specific angle profile. In addition, the viewing direction of the observer is not limited to the direction perpendicular to the display image (for example, directly in front of the display image), but varies depending on the application and installation location of the display device. Therefore, regardless of the value of ambient illuminance, the characteristic of the reflection component changes depending on the ambient illuminance condition and the viewing condition, and thus it is difficult to control the optimum gradation-luminance characteristic.

  The present invention has been made to solve these problems, and an object of the present invention is to provide a liquid crystal display device capable of obtaining an optimum gradation-luminance characteristic in a viewing direction regardless of ambient illuminance conditions.

  In order to solve the above-described problems, a liquid crystal display device according to the present invention includes a display region for displaying an image and a peripheral portion thereof, and a light detection device having the same configuration as a pixel disposed in the peripheral portion and disposed in the display region. Based on the illuminance sensor that is arranged in a predetermined positional relationship with the pixel for light detection at the peripheral portion and detects light incident from the pixel for light detection, and the illuminance value detected by the illuminance sensor And a conversion circuit for converting the gradation-luminance characteristics of the display image.

  According to the present invention, the light detection pixels arranged in the peripheral portion and having the same configuration as the pixels arranged in the display region, and the light detection pixels are arranged in the peripheral portion in a predetermined positional relationship from the light detection pixels. Since it includes an illuminance sensor that detects incident light and a conversion circuit that converts the gradation-luminance characteristics of the display image in the display area based on the illuminance value detected by the illuminance sensor, Therefore, an optimum gradation-luminance characteristic can be obtained in the viewing direction.

It is a figure which shows the liquid crystal display device by Embodiment 1 of this invention, and the photon detection area | region provided in the said liquid crystal display device. It is a figure which shows the AA cross section of FIG. 1 by Embodiment 1 of this invention. It is a figure which shows the BB cross section of FIG. 1 by Embodiment 1 of this invention. It is a figure which shows the positional relationship of the liquid crystal display device by Embodiment 1 of this invention, and a viewer. It is a block diagram of the liquid crystal display device by Embodiment 1 of this invention. It is a figure which shows the gradation-relative luminance characteristic of the display image by Embodiment 1 of this invention. It is a figure which shows the AA cross section of FIG. 1 by Embodiment 2 of this invention. It is a figure which shows the BB cross section of FIG. 1 by Embodiment 2 of this invention. It is a figure which shows the AA cross section of FIG. 1 by Embodiment 3 of this invention. It is a figure which shows the BB cross section of FIG. 1 by Embodiment 3 of this invention. It is a figure which shows an example of the change of the display brightness with respect to ambient illuminance in transflective LCD by a base technology. It is a figure which shows an example of the gradation-relative luminance characteristic in the transflective LCD by a premise technique. It is a figure which shows an example of the gradation-relative luminance characteristic of the display image visually recognized in the transflective LCD by a base technology. It is a figure which shows the positional relationship with a light source in the case of visually recognizing the transflective LCD by a base technology from the direction of (theta). It is a figure which shows the positional relationship of the illumination intensity sensor and light source in transflective LCD by a base technology.

  Embodiments of the present invention will be described below with reference to the drawings.

<Prerequisite technology>
First, the technology that is the premise of the present invention will be described.

  FIG. 11 is a diagram illustrating an example of a change in display luminance with respect to ambient illuminance in a transflective LCD according to the base technology. As described above, a transflective LCD uses light mainly composed of a transmissive component when the ambient illuminance is low, and uses light mainly composed of a reflective component when the ambient illuminance is high. Therefore, as shown in FIG. 11, sufficiently high display luminance can be obtained by the effect of the reflection component even when the ambient illuminance is high.

  FIG. 12 is a diagram showing an example of gradation-relative luminance characteristics in the transflective LCD according to the base technology. As shown in FIG. 12, (T) shows the transmission component, and (R) shows the gradation-relative luminance characteristic of the reflection component. Since the transmission component and the reflection component have different optical paths, the gradation-relative luminance characteristics are also different. The display image visually recognized on the LCD is a combination of the reflection component and the transmission component at a predetermined ratio. For example, as shown by a broken line in FIG. 12, the transmission image is (T) and the reflection component ( R).

  However, as described above, when the ambient illuminance is high, the reflection component is mainly used, so that the intermediate gradation of the display image is viewed brightly (high brightness), and even if the same display image is displayed, the ambient illuminance is There is a problem that it is visually recognized as an image with different luminance. As a countermeasure for such a problem, conventionally, the brightness of the surrounding environment is detected by an illuminance sensor, and the gradation-luminance characteristics are controlled based on the detection result. Since the characteristics vary depending on ambient light conditions and viewing conditions, it is difficult to control the optimum gradation-luminance characteristics.

  FIG. 13 is a diagram illustrating an example of gradation-relative luminance characteristics of a display image visually recognized on the transflective LCD according to the base technology. As shown in FIG. 13, (T) shows the transmission component, and (R) shows the gradation-relative luminance characteristic of the reflection component. In an environment where various ambient ambient light exists, in the display image, the ratio between the transmitted component and the reflected component varies depending on the intensity of ambient ambient light, the irradiation direction, or the viewing direction. (A) and (B) shown in FIG. 13 show gradation-relative luminance characteristics when a transmissive component and a reflective component coexist, and (A) shows a case where the reflective component is larger than (B). It is a gradation-relative luminance characteristic.

  FIG. 14 is a diagram illustrating a positional relationship with the light source when the transflective LCD according to the base technology is viewed from the direction of θ. In FIG. 14, for example, highly parallel light such as sunlight is applied to the display surface of the LCD from the direction of the angle φ1 or the angle φ2 with respect to the normal to the display surface, and from the direction of the angle θ with respect to the normal. The positional relationship between the light source and the viewer when the viewer visually recognizes is shown. In FIG. 14, it is assumed that φ1≈θ and φ2 <θ. The display image viewed from the direction of the angle θ includes a reflection component and a transmission component, but when the reflection characteristic of the LCD has directivity in the regular reflection direction with respect to incident light, the direction of the angle φ1 , The ratio of the reflection component is larger than the incident light from the direction of the angle φ2.

  On the other hand, FIG. 15 is a diagram showing the positional relationship between the illuminance sensor 30 and the light source in the transflective LCD according to the base technology. As shown in FIG. 15, the detection surface of the illuminance sensor 30 is parallel to the image display surface. When installed at a position, the magnitude of the detected illuminance is greater for incident light from the direction of angle φ2 than for incident light from the direction of angle φ1. In the LCD, since the gradation-luminance characteristic is controlled so as to correct the gradation in order to reduce the luminance of the reflection component that becomes stronger as the illuminance increases, the incident light from the direction of the angle φ2 at which the illuminance is detected is greatly increased. Is judged to have a large amount of reflection component, and gradation-luminance characteristics are controlled so as to lower the intermediate gradation.

  Thus, in FIG. 14, the incident light from the direction of the angle φ1 has a larger ratio of the reflected component than the incident light from the direction of the angle φ2, whereas in FIG. 15, the incident light from the direction of the angle φ2 The ratio of the reflection component is larger for light. That is, in the illuminance sensor 30 installed as shown in FIG. 15, the phenomenon that the ratio of the reflection component becomes larger in the incident light from the direction of the angle φ1 as shown in FIG. 14 cannot be detected. Therefore, there has been a problem that the optimum gradation-luminance characteristics cannot be controlled with respect to ambient light conditions.

  The present invention has been made to solve the above problems, and will be described in detail below.

<Embodiment 1>
FIG. 1 is a diagram showing a liquid crystal display device according to Embodiment 1 of the present invention and a light detection region provided in the liquid crystal display device. As shown in FIG. 1, a light detection region 8 is provided outside the display region (periphery) of the liquid crystal display device. In the light detection region 8, a light detection pixel 9 having a reflection portion 91 and a transmission portion 92 having the same configuration as the display pixel formed in the display region is formed. In addition, an illuminance sensor 11 that detects light incident from the light detection pixel 9 is provided at a peripheral portion in a predetermined positional relationship with the light detection pixel 9.

  In the liquid crystal display device according to the present embodiment, both the reflection unit that reflects the ambient light and displays the screen and the transmission unit that transmits the light from the backlight and displays the screen are included in one pixel. A transflective liquid crystal display device (hereinafter also referred to as an LCD) is provided. In the first embodiment, it is assumed that the viewer visually recognizes the display image from the right direction of the LCD (see FIG. 4), and the illuminance sensor 11 in the light detection region 8 is connected to the light detection pixel 9. It is assumed that it is provided on the side opposite to the display area (the right side of the light detection pixel 9 in FIG. 1).

  2 is a view showing a cross section AA in FIG. 1, and FIG. 3 is a view showing a cross section BB in FIG. As shown in FIGS. 2 and 3, a color filter side polarizing plate 2 is provided on the front side of the color filter substrate 1, and a liquid crystal layer 5 and a TFT (Thin Film Transistor) are provided on the back side of the color filter substrate 1. A substrate 3 and a TFT side polarizing plate 4 are sequentially provided. The liquid crystal layer 5 is formed by sealing liquid crystal between the color filter substrate 1 and the TFT substrate 3, and light is irradiated from a backlight 6 provided on the back side of the TFT side polarizing plate 4. The display area 7 is an area where display pixels are formed, and the reflection portion 91 and the transmission portion 92 of the light detection pixel 9 are formed in the light detection area 8 outside (peripheral edge) of the display area 7.

In the light detection region 8, a light shielding layer 10 is formed on the backlight 6 side of the color filter substrate 1, and the light detection pixel 9 of the light shielding layer 10 is formed in the display region 7. An opening having the same size as the pixel is provided. The illuminance sensor 11 is closely attached to the color filter side polarizing plate 2 so that the light receiving surface 12 is on the color filter side polarizing plate 2 side, and the light receiving surface 12 is a light shielding layer provided at a location where the light detection pixels 9 are formed. The area is about the same as the 10 openings. The center position of the illuminance sensor 11 is opposite to the display area 7 (at the end of the LCD) from the intersection with the color filter side polarizing plate 2 orthogonal to the perpendicular H passing through the center of the light detection pixel 9. Is set to be shifted by a predetermined distance d. That is, the distance d is the distance in the display area surface direction between the light detection pixel 9 and the illuminance sensor 11. Here, the distance d is the sum of the thicknesses of the color filter substrate 1 and the color filter side polarizing plate 2 (the distance from the arrangement position of the light detection pixels 9 to the arrangement plane of the illuminance sensor 11) t. Then
d = t × tan θ (1)
The illuminance sensor 11 is installed so that The angle θ in the formula (1) is an angle formed between the perpendicular H passing through the center of the LCD and the viewing direction (an angle formed between the perpendicular to the display region 7 passing through the center of the display region 7 and the viewing position direction). The range is 0 ° <θ <90 °. In the first embodiment, it is assumed that the viewing position is defined as a specific position with respect to the display area of the LCD.

In the above description, the color filter substrate 1, the color filter side polarizing plate 2, and the refractive index of air are not considered, but actually, the illuminance is based on Snell's law in consideration of these refractive indexes. The position of the sensor 11 is set. Specifically, the distance d ′ between the intersection of the perpendicular H and the color filter side polarizing plate 2 and the center position of the illuminance sensor 11 (distance in the display area surface direction between the light detection pixel 9 and the illuminance sensor 11) is ,
d ′ = t × tan θ ′ (2)
And θ ′ is
sin θ ′ = (n / n ′) × sin θ (3)
Because
d ′ = t × {[(n / n ′) ² × (sin θ) ² ] / [1- (n / n ′) ² × (sin θ) ² ]} ^0.5 (4)
It becomes. Here, n is the refractive index of the air layer, n ′ is the refractive index of the color filter substrate 1 (specifically, the thicknesses of the respective refractive indexes of the color filter substrate 1 and the color filter side polarizing plate 2 are weighted. Average refractive index).

  Next, the operation in the light detection region 8 will be described with reference to FIGS.

  In FIG. 2, the light incident on the light detection pixel 9 in the same manner as the light incident on the pixels in the display area 7 out of the ambient light is reflected by the reflection portion 91 of the light detection pixel 9. Of the reflected light, only the light reflected in the direction of the angle θ is detected by the illuminance sensor 11. On the other hand, in FIG. 3, the light incident on the light detection pixel 9 from the backlight 6 is transmitted through the transmission portion 92 of the light detection pixel 9, and only the light transmitted in the direction of the angle θ of the transmitted light is transmitted. It is detected by the illuminance sensor 11. As described above, the light detected by the illuminance sensor 11 is light in the same direction as the viewing direction (angle θ shown in FIG. 4) with respect to the display image. The component of the reflected light (reflection component) and the component of the light transmitted through the transmission part 92 (transmission component) are included, and the ratio of these reflection component and transmission component is the ratio of the display image visually recognized by the viewer The ratio between the reflection component and the transmission component is the same. That is, the visual recognition position for visually recognizing the image is defined as a specific position with respect to the display area 7, and the predetermined positional relationship between the light detection pixel 9 and the illuminance sensor 11 is similar to the positional relationship between the display area 7 and the visual recognition position. It becomes a relationship.

  Next, a method of controlling the liquid crystal display device based on the illuminance magnitude (illuminance value) detected by the illuminance sensor 11 will be described with reference to FIGS.

  FIG. 5 is a block diagram of the liquid crystal display device according to the first embodiment of the present invention. As shown in FIG. 5, the signal based on the illuminance value detected by the illuminance sensor 11 is A / D converted by the A / D conversion circuit 13 and then converted to the illuminance value by the timing control circuit 17 (conversion circuit). Based on this, the gradation-relative luminance characteristic of the display image is controlled (converted) and then output to the display area. The timing control circuit 17 includes a data conversion table 14, a data conversion circuit 15, and a synchronization signal control circuit 16, and is a circuit that controls the gradation-relative luminance characteristics of the display image based on the illuminance value.

  FIG. 6 is a diagram showing the gradation-relative luminance characteristics of the display image according to Embodiment 1 of the present invention. For example, the gradation-relative luminance characteristics (t) in the case where the ambient illuminance is substantially zero are different from the gradation-relative luminance characteristics (t) when the ambient illuminance is changed to La, Lb, and Lc. ) And (c), the case where each gradation-relative luminance characteristic is controlled to become a characteristic close to (t) will be described.

  As shown in FIG. 6, when the illuminance is La, the relative luminance at the gradation G (t) is B (t) when the ambient illuminance is substantially zero, but B when the illuminance is La. Since (a), the gradation is read from G (t) to G (a) in order to change the relative luminance from B (a) to B (t). Similarly, when the illuminance is Lb, the relative luminance at the gradation G (t) is B (b). Therefore, in order to change the relative luminance from B (b) to B (t), the gradation is set to G. Read (convert) from (t) to G (b). The above replacement is performed by the data conversion circuit 15 shown in FIG.

  The above data is reread for each gradation under each illuminance condition. Gradation data used for reading is stored in the data conversion table 14 of the timing control circuit 17 by measuring gradation-luminance characteristics while changing the illuminance condition in advance on an actual LCD.

  From the above, according to the configuration according to the first embodiment, the illuminance sensor 11 can detect the illuminance of light in the direction of the same angle as the viewing direction with respect to the display image. Therefore, since optimum gradation-luminance characteristics can be obtained in the viewing direction regardless of ambient illumination conditions such as ambient light intensity and irradiation direction, the display image is controlled based on the gradation-luminance characteristics. The viewer can visually recognize the optimum display image.

  In the first embodiment, it is assumed that the viewer visually recognizes the display image on the LCD from the right direction, and the illuminance sensor 11 is opposite to the display region with respect to the light detection pixel 9 (in FIG. However, when the display image is viewed from the left side of the LCD, the illuminance sensor 11 is placed on the display area side with respect to the light detection pixel 9 (on the left side of the light detection pixel 9 in FIG. 1). ). When the display image is viewed from above the LCD, the illuminance sensor 11 is provided on the upper side of the light detection pixel 9, and when the display image is viewed from below the LCD, the illuminance sensor 11 is detected by light. It is provided below the working pixel 9. Furthermore, by providing a plurality of positional relationships between the light detection pixels 9 and the illuminance sensor 11, it is possible to visually recognize an optimal display image with respect to the plurality of viewing directions. That is, the illuminance sensor 11 is arranged at any one of the upper, lower, left, and right positions or a plurality of positions with respect to one light detection pixel 9.

  Further, in the first embodiment, the light detection area is described on the right side outside the display area (periphery) of the LCD. A plurality of light detection regions may be provided at each position (right side, left side, upper side, lower side). That is, a set of a light detection pixel and an illuminance sensor may be provided in each of a plurality of different locations on the peripheral edge.

  In the first embodiment, the case of a transflective type liquid crystal display device has been described. However, the present invention can be applied to a case of a micro-reflection type, a transmission type, and a reflection type.

<Embodiment 2>
The second embodiment of the present invention is characterized in that a light reflection layer and a light absorption layer are provided on the front and back surfaces of the color filter substrate 1, respectively. Other configurations and operations are the same as those in the first embodiment, and thus description thereof is omitted here.

  7 is a view showing a cross section AA in FIG. 1, and FIG. 8 is a view showing a cross section BB in FIG. As shown in FIGS. 7 and 8, the light reflecting layers 18, 19, 20, 21 and the light absorbing layers 22, 23, 24, 25 are provided on the front and back surfaces of the color filter substrate 1. That is, the light reflection layers 18, 19, 20, 21 and the light absorption layers 22, 23, 24, 25 are on the illuminance sensor 11 side of the color filter substrate 1 arranged between the light detection pixels 9 and the illuminance sensor 11. And the surface on the light detection pixel 9 side are provided in an alternating arrangement. The light reflecting layers 18, 19, 20, and 21 and the light absorbing layers 22, 23, 24, and 25 are approximately the same size as the pixels formed in the display area. As shown in FIG. 4, the formation position of the absorption layer) is the light reflected by the reflecting portion 91 of the light detection pixel 9, where θ is the angle formed between the perpendicular H passing through the center of the LCD and the viewing direction. In addition, the light transmitted through the transmission part 92 is formed at such a position as to be incident on the illuminance sensor 11 at an angle θ after being reflected by the light reflection layers 18, 19, 20, and 21 at an angle θ. In the second embodiment, as shown in FIGS. 7 and 8, the light reflecting layers are formed on the both sides of the color filter substrate 1 at two places, four places in total. In the second embodiment, a total of four light reflecting layers and light absorbing layers are formed. However, the number of light reflecting layers and light absorbing layers is not limited to four and may be provided at a plurality of locations.

  Next, the operation in the light detection region 8 will be described with reference to FIGS.

  In FIG. 7, the light incident on the light detection pixel 9 in the same manner as the light incident on the pixels in the display region 7 out of the ambient light is reflected by the reflection portion 91 of the light detection pixel 9, and Of the reflected light, only the light reflected in the direction of the angle θ is detected by the illuminance sensor 11 after being sequentially reflected by the light reflecting layers 18, 19, 20, and 21. On the other hand, in FIG. 8, the light incident on the light detection pixel 9 from the backlight 6 is transmitted through the transmission part 92 of the light detection pixel 9, and only the light transmitted in the direction of the angle θ among the transmitted light is transmitted. The light reflection layers 18, 19, 20, and 21 are sequentially reflected and detected by the illuminance sensor 11. That is, the light from the light detection pixel 9 is incident on the illuminance sensor 11 after being reflected by the light reflection layer a plurality of times in the color filter substrate 1. As described above, the light detected by the illuminance sensor 11 is light in the same direction as the viewing direction (angle θ shown in FIG. 4) with respect to the display image. The component of the reflected light (reflection component) and the component of the light transmitted through the transmission part 92 (transmission component) are included, and the ratio of these reflection component and transmission component is the ratio of the display image visually recognized by the viewer The ratio between the reflection component and the transmission component is the same.

  As in the first embodiment, the signal based on the illuminance value detected by the illuminance sensor 11 is based on the gradation-luminance characteristic replacement gradation data that is calculated in advance and set in the data conversion table 14 of FIG. To convert.

  From the above, according to the configuration according to the second embodiment, the illuminance sensor 11 can detect the illuminance of light in the direction of the same angle as the viewing direction with respect to the display image. Therefore, since optimum gradation-luminance characteristics can be obtained in the viewing direction regardless of ambient illumination conditions such as ambient light intensity and irradiation direction, the display image is controlled based on the gradation-luminance characteristics. The viewer can visually recognize the optimum display image. Further, since the light reflection layers 18, 19, 20, 21 and the light absorption layers 22, 23, 24, 25 are provided, the illuminance sensor 11 can be installed at a position away from the light detection pixels 9. Accordingly, since there is no light blocking object (for example, the illuminance sensor 11) on the color detection substrate 1 side of the light detection pixel 9, the restriction on the incident direction of ambient light and the restriction on the light detection direction (viewing direction) are reduced. That is, the illuminance sensor 11 can be arranged on either the top, bottom, left, or right side of the light detection pixel 9, and the installation of the illuminance sensor 11 is not limited by the viewing direction.

  In the second embodiment, it is assumed that the viewer visually recognizes the display image on the LCD from the right direction, and the illuminance sensor 11 is opposite to the display region with respect to the light detection pixel 9 (in FIG. However, when the display image is viewed from the left side of the LCD, the illuminance sensor 11 is placed on the display area side with respect to the light detection pixel 9 (on the left side of the light detection pixel 9 in FIG. 1). ). When the display image is viewed from above the LCD, the illuminance sensor 11 is provided on the upper side of the light detection pixel 9, and when the display image is viewed from below the LCD, the illuminance sensor 11 is detected by light. It is provided below the working pixel 9. Furthermore, by providing a plurality of positional relationships between the light detection pixels 9 and the illuminance sensor 11, it is possible to visually recognize an optimal display image with respect to the plurality of viewing directions.

  In the second embodiment, the light detection area is arranged on the right side outside the display area (periphery) of the LCD. A plurality of light detection regions may be provided at each position (right side, left side, upper side, lower side).

  In the second embodiment, the case of a transflective type liquid crystal display device has been described. However, the present invention can also be applied to a case of a fine reflection type, a transmission type, and a reflection type.

<Embodiment 3>
Embodiment 3 of the present invention is characterized in that a two-dimensional image sensor is provided as an illuminance sensor. Other configurations and operations are the same as those in the first embodiment, and thus description thereof is omitted here.

  FIG. 9 is a view showing a cross section AA in FIG. 1, and FIG. 10 is a view showing a cross section BB in FIG. As shown in FIG. 9, the two-dimensional image sensor 26 is closely attached to the color filter side polarizing plate 2 so that the light receiving surface 12 is on the color filter side polarizing plate 2 side. The two-dimensional image sensor 26 may be a CCD (Charge Coupled Device) type sensor array, a CMOS (Complementary Metal Oxide Semiconductor) type sensor array, or the like. .

  In the first and second embodiments, since the positional relationship between the light detection pixel 9 and the illuminance sensor 11 is fixed, it is possible to detect light that matches the viewing direction, but the viewing direction from the viewer with respect to the LCD is It was limited to one direction assumed beforehand. On the other hand, in the third embodiment, since the two-dimensional image sensor 26 is used, the light receiving surface is not a single point, so the light detection position can be arbitrarily selected within the light receiving surface, and the viewing direction from the viewer with respect to the LCD However, the effect of the present invention can be obtained not only in one direction but also in a somewhat free direction (a viewing direction within a predetermined angle range with respect to the display screen).

  Next, the operation in the light detection region 8 will be described with reference to FIGS. 9 and 10.

  In FIG. 9, the light incident on the light detection pixel 9 in the same manner as the light incident on the pixels in the display region 7 out of the ambient light is reflected by the reflection portion 91 of the light detection pixel 9 and is 2 It is detected by the dimensional image sensor 26. On the other hand, in FIG. 10, the light incident on the light detection pixel 9 from the backlight 6 passes through the transmission portion 92 of the light detection pixel 9 and is detected by the two-dimensional image sensor 26.

Here, for example, as shown in FIGS. 9 and 10, when viewing from an angle θ1 with respect to a perpendicular passing through the center of the LCD,
d = t × tan θ1 (5)
The light intensity at the point P1 of the light receiving surface 12 of the two-dimensional image sensor 26 determined in step S1 is detected.

For example, when viewing from the angle θ2 with respect to a perpendicular passing through the center of the LCD,
d = t × tan θ2 (6)
The light intensity at the position P2 of the light receiving surface 12 of the two-dimensional image sensor 26 determined in step S2 is detected.

  As described above, the light detected at the points P1 and P2 of the light receiving surface 12 of the two-dimensional image sensor 26 is light in the same direction as the viewing direction (θ1, θ2) with respect to the display image, and the two-dimensional image sensor. 26 includes a component of light reflected by the reflection unit 91 (reflection component) and a component of light transmitted through the transmission unit 92 (transmission component). These reflection components and transmission components are included in the light. Is the same as the ratio of the reflection component and the transmission component of the display image visually recognized by the viewer.

  As in the first and second embodiments, the signal based on the illuminance value detected by the two-dimensional image sensor 26 is calculated in advance, and the gradation-luminance characteristic reading level set in the data conversion table 14 of FIG. Convert based on key data.

  From the above, according to the configuration according to the third embodiment, an optimum gradation-luminance characteristic can be obtained in a viewing direction within a predetermined angle range with respect to the display screen regardless of the ambient illuminance condition. By controlling the display image based on the gradation-luminance characteristics, the viewer can visually recognize the optimum display image.

  In the third embodiment, it is assumed that the viewer visually recognizes the display image on the LCD from the right direction, and the two-dimensional image sensor 26 is opposite to the display region with respect to the light detection pixel 9 (in FIG. 1). Although provided on the right side of the light detection pixel 9, when the display image is viewed from the left side of the LCD, the two-dimensional image sensor 26 is positioned on the display region side (in FIG. 1, for light detection). Provided on the left side of the pixel 9. Further, when the display image is viewed from above the LCD, the two-dimensional image sensor 26 is provided above the light detection pixel 9, and when the display image is viewed from below the LCD, the two-dimensional image sensor. 26 is provided below the light detection pixel 9. Further, by providing a plurality of positional relationships between the light detection pixels 9 and the two-dimensional image sensor 26, it is possible to visually recognize an optimal display image with respect to the plurality of viewing directions.

  In the third embodiment, the light detection region 8 is described on the right side outside the display region (periphery) of the LCD. Or a plurality of light detection regions at each position (right side, left side, upper side, lower side).

  In the third embodiment, the case of a transflective type liquid crystal display device has been described. However, the present invention can be applied to a case of a micro-reflection type, a transmission type, and a reflection type.

  DESCRIPTION OF SYMBOLS 1 Color filter substrate, 2 Color filter side polarizing plate, 3 TFT substrate, 4 TFT side polarizing plate, 5 Liquid crystal layer, 6 Backlight, 7 Display area, 8 Photodetection area, 9 Photodetection pixel, 91 Reflection part, 92 Transmission unit, 10 light shielding layer, 11 illuminance sensor, 12 light receiving surface, 13 A / D conversion circuit, 14 data conversion table, 15 data conversion circuit, 16 synchronization signal control circuit, 17 timing control circuit, 18, 19, 20, 21 Light reflection layer, 22, 23, 24, 25 Light absorption layer, 26 Two-dimensional image sensor, 30 Illuminance sensor.

Claims (8)

A display area for displaying an image and its peripheral edge;
A pixel for light detection that is disposed in the peripheral portion and has the same configuration as the pixel disposed in the display region;
An illuminance sensor that is disposed at a predetermined positional relationship obliquely facing the light detection pixel at the peripheral edge, and detects light incident from the light detection pixel;
A conversion circuit that converts a gradation-luminance characteristic of a display image in the display area based on an illuminance value detected by the illuminance sensor;
A liquid crystal display device comprising: The visual recognition position for visually recognizing the image is defined as a specific position with respect to the display area,
The liquid crystal display device according to claim 1, wherein the predetermined positional relationship between the light detection pixel and the illuminance sensor is similar to a positional relationship between the display region and the visual recognition position. The distance d in the display area plane direction between the light detection pixel and the illuminance sensor is:
An angle formed by a perpendicular to the display area passing through the center of the display area and the viewing position direction is θ (0 ° <θ <90 °), and is orthogonal to the light sensor placement surface from the light detection pixel placement position. Let t be the distance to
d = t × tan θ (1)
The liquid crystal display device according to claim 2, wherein the liquid crystal display device is a liquid crystal display device. The distance d in the display area plane direction between the light detection pixel and the illuminance sensor is:
An angle formed between a perpendicular to the display area passing through the center of the display area and the viewing position direction is θ (0 ° <θ <90 °), and the light detection pixel is arranged on the illuminance sensor arrangement surface. Assuming that the distance to the orthogonal is t, the refractive index of the air layer is n, and the refractive index of the color filter substrate disposed between the distances t is n ′,
d = t × {[(n / n ′) ² × (sin θ) ² ] / [1- (n / n ′) ² × (sin θ) ² ]} ^0.5 (2)
The liquid crystal display device according to claim 2, wherein the liquid crystal display device is a liquid crystal display device. A color filter substrate disposed between the light detection pixel and the illuminance sensor;
Further comprising light reflecting layers and light absorbing layers provided in an alternating arrangement on each of the surface on the illuminance sensor side of the color filter substrate and the surface on the pixel side for light detection,
3. The liquid crystal display according to claim 1, wherein light from the light detection pixel is incident on the illuminance sensor after being reflected by the light reflection layer a plurality of times in the color filter substrate. apparatus.   The liquid crystal display device according to claim 1, wherein the illuminance sensor is a two-dimensional image sensor.   The illuminance sensor is arranged at any one of the upper, lower, left and right positions or a plurality of positions with respect to one of the light detection pixels. Liquid crystal display device.   The liquid crystal display device according to claim 1, further comprising a set of the light detection pixel and the illuminance sensor at a plurality of different locations on the peripheral edge.

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