JP2010191188A - Backlight, control method thereof, liquid crystal display device and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily avoid a phenomenon that a screen end portion becomes darker than the screen center when successively emitting light from a plurality of light emitting areas, in a backlight for irradiating a liquid crystal display panel with light. <P>SOLUTION: A light source driving circuit is configured to successively turn on first to sixth-area light sources with a luminance of 100%. The first-area light source positioned at the uppermost end of the screen is turned on with a luminance of 60% at the timing before the timing of turning on with a luminance of 100%, and also, the first-area light source is turned on with a luminance of 20% before the timing. The sixth-area light source positioned at the downmost end of the screen is turned on with a luminance of 60% after the timing of turning on with a luminance of 100%, further, the sixth-area light source is turned on with a luminance of 20% at the timing after the subsequent timing. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technique for uniformly irradiating light from the back side of a liquid crystal display panel.

  A liquid crystal display device used as a display unit of an information terminal device such as a mobile phone is visualized by irradiating light onto a light modulation image by a liquid crystal display panel. Liquid crystal display panels are broadly divided into transmissive and reflective types, but the transmissive type that turns on the backlight installed on the back side of the panel can better see high-quality images even in dark places. There are many advantages. By the way, the liquid crystal display panel generates a feeling of afterimage when displaying a moving image. For this reason, a technique has been proposed in which the light emission area of the backlight is divided into a plurality of areas and each area emits light intermittently in synchronization with the scanning of the liquid crystal display panel (see Patent Document 1).

JP 2002-182182 A (FIG. 1)

However, when the light emitting area is divided into a plurality of areas and each area is caused to emit light intermittently, a problem has arisen that the edge of the screen becomes darker than the center of the screen.
The present invention has been made in view of the above-described circumstances, and one of its purposes is to divide the light emitting area into a plurality of areas and to intermittently emit light in each area. The object is to provide a technique capable of easily avoiding the phenomenon of darker than the center.

In order to solve the above problems, the backlight according to the present invention is provided corresponding to each of a plurality of areas in which the display area of the liquid crystal display panel is divided along one direction and arranged side by side in the other direction, A plurality of light sources that respectively irradiate light to each of the regions from the back side of the liquid crystal display panel, and a plurality of the light sources are turned on with a first luminance at a predetermined timing in a predetermined order. Among the light sources, a light source that lights a light source positioned at an end in the array of the regions at a second luminance that is darker than the first luminance at a timing before or after the timing at which the light is lit at the first luminance. And a driving circuit. According to the present invention, it is eliminated that the area located at the end is darker than the other areas.
In the present invention, the one direction is a direction in which the scanning lines of the liquid crystal display panel extend, and the other direction is a direction in which the data lines of the liquid crystal display panel extend, from the first region to the Nth ( N is an integer of 3 or more), and the light source drive circuit turns on the light source of the first region when the light source driving circuit sequentially lights from the light source of the first region to the light source of the N region with a first luminance. The second luminance is lit at a timing before the timing at which the first luminance is lit, and the second luminance at a timing after the timing at which the light source in the Nth region is lit at the first luminance. It may be turned on. According to this configuration, the luminance change in the first region and the Nth region approaches the luminance change in the other regions, so that the luminance perceived by a person can be made uniform.
In the present invention, when N is an integer of 5 or more, the light source driving circuit has the second timing at a timing before the timing at which the light source in the first region is lit at the second luminance. The light source may be lit darker than the luminance, and the light source of the Nth region may be lit darker than the second luminance at a timing prior to the timing when the light source is lit at the second luminance. The light source is lit darker than the second luminance at a timing before the timing at which the first luminance is turned on, and the light source in the (N-1) region is turned on at the first luminance. It may be lit darker than the second luminance at the previous timing. In this way, the influence of light leakage from a remote area is also reduced, so that the brightness of the screen can be made more uniform.
In addition to the backlight, the present invention can be conceptualized as a backlight control method, a liquid crystal display device, and an electronic device.

It is a figure which shows the structure of the liquid crystal display device which concerns on embodiment. It is a figure which shows the relationship between a screen area | region and a light emission area | region. It is a figure which shows the structure of a light source drive circuit. It is a figure which shows the relationship between the count value in a light emission amount instruction | indication circuit, and instruction | indication light emission amount. It is a figure which shows an example of a structure of the light emission amount instruction | indication circuit. It is a figure which shows temporal transition with the irradiation amount in each screen area | region. It is a figure which shows the scroll of the light emission area with respect to a screen. It is a figure which shows the time change of the brightness | luminance in each part of a screen. It is a figure which shows the structure of the mobile telephone to which the liquid crystal display device which concerns on embodiment is applied. It is a figure which shows that the brightness of a screen becomes non-uniform | heterogenous in a comparative example. It is a figure which shows the time change of the brightness | luminance in each part of the screen in a comparative example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of a liquid crystal display device according to an embodiment.
As shown in this figure, the liquid crystal display device 1 includes a liquid crystal display panel 100, a display control circuit 20, and a backlight 30. The liquid crystal display device 1 is supplied with the video data Vd from the upper circuit in synchronization with the synchronization signal Sync. This video data Vd designates a gradation level for each pixel of the liquid crystal display panel 100, and is used as a vertical scanning signal, a horizontal scanning signal, and a dot clock signal (all not shown) included in the synchronization signal Sync. Therefore, they are supplied in the order of the scanned pixels.

The liquid crystal display panel 100 is, for example, an active matrix transmissive type, and 600 lines of scanning lines 112 extend in the X (horizontal) direction in the figure in the display region, and 3 m (m Is an integer) columns of data lines 114 extending in the Y (vertical) direction in the figure and provided so as to be electrically insulated from each scanning line 112, and these scanning lines 112 and data lines 114. Pixels 110 are respectively arranged corresponding to the intersections. The area where the pixels 110 are arranged in this way is the display area 101.
The three pixels 110 corresponding to the intersections of the scanning lines 112 in one row and the three data lines 114 adjacent to each other correspond to R (red), G (green), and B (blue), respectively. It is configured to represent the color of one dot with three pixels of RGB.
The pixel 110 has a well-known liquid crystal element in which a liquid crystal layer is sandwiched between a pixel electrode and a common electrode, although details are not shown in detail. That is, in the liquid crystal element in the pixel 110, when the scanning line 112 is selected, the data signal supplied to the data line 114 is applied to the pixel electrode, and the voltage is held by the pixel electrode and the common electrode. The transmittance is high.

The display control circuit 20 controls the operation of each unit in accordance with the synchronization signal Sync supplied from the upper circuit.
The Y driver 130 selects the scanning lines 112 in the order of the first, second, third,..., And 600th rows over the frame in accordance with the control by the display control circuit 20, and applies the selection voltage to the selected scanning lines. The scanning line driving circuit applies a non-selection voltage to each scanning line.
Note that a frame refers to a period required to display one frame of an image by driving the liquid crystal display panel 100. If the frequency of the vertical scanning signal included in the synchronization signal Sync is 60 Hz, the reciprocal thereof. 16.7 milliseconds.
The X driver 140 converts the video data Vd into an analog data signal according to the control by the display control circuit 20, and outputs the converted data signal to each of the pixels 110 for one row selected by the Y driver 130. These are data line driving circuits that are supplied via the data lines 114, respectively.

The backlight 30 includes light sources 31 to 36 and a light source driving circuit 40. Here, FIG. 2A is a plan view showing the light emitting area of the backlight 30 in relation to the display area 101, and FIG. 2B is an end view showing the configuration of the backlight 30.
As shown in these drawings, the light emission area by the backlight 30 is obtained by dividing six areas obtained by dividing the display area 101 along the X direction that is the extending direction of the scanning lines into Y that is the extending direction of the data lines. The first to sixth regions are arranged in order from the top. That is, in the present embodiment, N is “6”. Here, the division of the display area means not a physical division but a convenient division.

Here, the first area corresponds to the 1st to 100th lines of the scanning line, and similarly, the second area corresponds to the 101st to 200th lines of the scanning line, and the third area corresponds to the scanning line. Corresponding to the 201st to 300th lines, the fourth area corresponds to the 301st to 400th lines of the scanning line, the fifth area corresponds to the 401st to 500th lines of the scanning line, and the sixth area corresponds to the scanning line. Corresponds to the 501st to 600th lines.
The light irradiation sources in the first to sixth regions are the light sources 31 to 36, respectively, and, for example, white LEDs are used in the present embodiment.

As shown in FIG. 2B, the backlight 30 is a back direct type in which the light sources 31 to 36 are disposed on the back side of the liquid crystal display panel 100, and the light sources 31 to 36 are formed by partition walls that also serve as reflectors. In the liquid crystal display panel 100, light is applied to a corresponding region.
Although the backlight 30 is of a type directly under the back surface, the light sources 31 to 36 are provided on the side surface side of the liquid crystal display panel 100, and the irradiation light is guided to the back side of each region by a light guide or the like. Various configurations such as a side edge type in which light is irradiated from the back side of the panel 100 can be applied.

In the present embodiment, although the light emitting area is divided into the first to sixth areas, actually, the light emitting area is emitted from a light source in a certain area due to a gap or diffraction when the backlight 30 is assembled to the liquid crystal display panel 100. It is assumed that the incident light leaks into the adjacent area.
For example, the light emitted from the light source 33 corresponding to the third region is incident not only on the pixels 110 in the third region but also on the pixels in the second and fourth regions adjacent to the third region due to leakage, Enters the pixels in the first and fifth regions. Of course, the degree of light leakage decreases with increasing distance from the area of the light source to be lit.

The light source driving circuit 40 drives the light sources 31 to 36 in accordance with the synchronization signal Sync, and a detailed configuration will be described with reference to FIGS.
FIG. 3 is a diagram illustrating a configuration of the light source driving circuit 40. As shown in this figure, the light source drive circuit 40 includes a line counter 42, a light emission amount instruction circuit 400, D / A conversion circuits (DACs) 411 to 416, and amplification circuits 421 to 426.
Among these, the line counter 42 counts up the count value Ca by “1” every time the start of horizontal scanning is instructed by the horizontal scanning signal Hsync included in the synchronizing signal Sync, and the count value Ca is used as the synchronizing signal Sync. When the vertical scanning start is instructed by the included vertical scanning signal Vsync, it is reset to zero.

  The light emission amount instruction circuit 400 outputs the light emission amount instruction values Cb1 to Cb6 according to the count value Ca as shown in FIG. When the light emission amount instruction values Cb1 to Cb6 are converted into decimal values, any one of “0”, “25”, “50”, “75”, “150”, and “255” is output. For example, if the count value Ca is “250”, the light emission amount instruction circuit 400 is “150” as the light emission amount instruction value Cb1, “25” as Cb2, “0” as Cb3 and Cb4, “75” as Cb5, “255” is output as Cb6.

The DAC 411 converts the light emission amount instruction value Cb1 into an analog voltage, and the amplifier circuit 421 appropriately amplifies the analog voltage and supplies the analog voltage to the light source 31. Similarly, for the DACs 412 to 416, the light emission amount instruction values Cb2 to Cb6 are converted into analog voltages, respectively, and the amplifier circuits 422 to 426 amplify the converted analog voltages and supply them to the light sources 32 to 26.
Here, regarding the light emission amount instruction values Cb1 to Cb6, assuming that “0” is the lowest value and “255” is the highest value, when the light emission amount instruction value is “0”, the light source is turned off. On the other hand, when the light emission amount instruction value is “255”, the light source is turned on at the maximum luminance (relative luminance 100%). Further, when the light emission amount instruction values are “25”, “50”, “75”, and “150”, respectively, the light sources are turned on at relative luminances of 10%, 20%, 30%, and 60%, respectively.

Here, as a specific configuration of the light emission amount instruction circuit 400 that outputs the light emission amount instruction values Cb1 to Cb6 according to the count value Ca, for example, the one shown in FIG.
The light emission amount instruction circuit 400 shown in FIG. 5 includes a decoder, six JK-FFs (flip-flops), and six selectors (SEL). Of these, the decoder has a count value Ca of “0”, When “100”, “200”, “300”, “400”, and “500”, a signal that is at H level is output from each terminal. JK-FF sets the output terminal Q to H level when the input terminal J becomes H level, and resets the output terminal Q to L level when the input terminal K becomes H level. . The selector selects the data supplied to the input terminals a, b, and c only when the selection terminals Sel-a, Sel-b, and Sel-c become H level, respectively, and selects the selection terminals Sel-a, Sel- If b and Sel-c are both at the L level, the data supplied to the input terminal d is selected, and the data supplied to the selected input terminal is output as the light emission amount instruction value.
Note that FIG. 5 is merely an example of the light emission amount instruction circuit 400. In addition, the light emission amount instruction circuit 400 may be configured by a lookup table or the like in which the conversion contents shown in FIG. 4 are stored in advance.

Next, the operation of the liquid crystal display device 1 will be described.
The video data Vd includes 1 row, 1 column to 1 row (3n) column, 2 rows, 1 column to 2 rows (3n) column, 3 rows, 1 column to 3 rows (3n) column,..., 600 rows and 1 column in each frame. Supplied in order of pixels of ~ 600 rows (3n) columns.

The operation of the liquid crystal display panel 100 will be described. In the horizontal scanning period in which the video data Vd of 1 row 1 column to 1 row (3n) column is supplied, the display control circuit 20 follows the Y driver 130 and the X driver 140 respectively. Control like this. That is, the display control circuit 20 causes the Y driver 130 to select the scanning line 112 in the first row, while causing the X driver 140 to convert the video data Vd into a data signal and from the first column ( 3n) Output to the data lines 114 up to the column.
As a result, since a data signal is applied to the pixel electrode in the pixel 110 in the first row, a voltage corresponding to the gradation specified by the video data Vd is written into the pixel 110 in the first row. .
When the second row of video data Vd is supplied, the display control circuit 20 causes the Y driver 130 to select the second row of scanning lines 112, while the X driver 140 sends the video data Vd to the data. The signal is converted into a signal and output to the data line 114 from the first column to the 3nth column. As a result, in the pixels 110 in the second row, a voltage corresponding to the gradation specified by the video data Vd is written.
Hereinafter, since the same operation is executed in the order of the third, fourth,..., 600th rows, a voltage corresponding to the gradation specified by the video data Vd is written in each pixel 110, and light modulation is performed. An image will be created.

Next, the operation of the backlight 30 for visualizing the light modulation image created in this way, particularly the light source driving circuit 40 will be described.
The line counter 42 resets the count value Ca to zero by the vertical synchronization signal Vsync at the start of the frame and outputs it. For this reason, in the horizontal scanning period in which the video data Vd of the first row is supplied, the light emission amount instruction circuit 400 sets only the light emission amount instruction value Cb4 to “255”, and the light emission amount instruction values Cb1 to Cb3, Cb5, and Cb6. Is “0”. Therefore, in the period in which writing is performed on the pixels in the first row in the liquid crystal display panel 100, only the light source 34 in the fourth region is turned on with 100% luminance, and the light sources 31 to 33, 35, and 36 in other regions are turned off. It becomes a state.
Subsequently, when the video data Vd in the second row is supplied, the line counter 42 counts up the count value Ca to “1”, but the light emission amount instruction circuit 400 uses the light emission amount instruction values Cb1 to Cb6. Do not change about. Accordingly, in the period in which writing is performed on the pixels in the second row in the liquid crystal display panel 100, only the light source 34 in the fourth region is turned on with 100% luminance, and the light sources 31 to 33, 35, and 36 in other regions are turned off. It becomes a state. Such a state continues until the video data Vd in the 100th row is supplied and the count value Ca reaches “99”.

  Subsequently, when the video data Vd in the 101st row is supplied, the line counter 42 counts up the count value Ca from “99” to “100”. Therefore, the light emission amount instruction circuit 400 sets the light emission amount instruction value Cb5 to “255”, Cb1 to “50”, and other light emission amount instruction values Cb2 to Cb4 and Cb6 to “0”. Therefore, in the period in which writing is performed on the pixels in the 101st row in the liquid crystal display panel 100, the light source 35 in the fifth region is lit with 100% luminance, and the light source 31 in the first region is lit with 20% luminance. The light sources 32 to 34 and 36 in other areas are turned off. This state continues until the video data Vd of the 200th row is supplied and the count value Ca becomes “199”.

When the video data Vd in the 201st row is supplied, the line counter 42 counts up the count value Ca to “200”. Therefore, the light emission amount instruction circuit 400 sets the light emission amount instruction value Cb6 to “255”, Cb1 to “150”, Cb5 to “75”, Cb2 to “25”, and other light emission amount instruction values Cb3, Cb4 is set to “0”. Therefore, in the period in which writing is performed on the pixels in the 201st row in the liquid crystal display panel 100, the light source 36 in the sixth region is lit with a maximum luminance of 100%, and the light source 31 in the first region is lit with a luminance of 60%. The light source 35 in the fifth area is turned on with a luminance of 30%, the light source 32 in the second area is turned on with a luminance of 10%, and the light sources 33 and 34 in the other areas are turned off. This state continues until the video data Vd in the 300th row is supplied and the count value Ca becomes “299”.
When the video data Vd in the 301st row is supplied, the line counter 42 counts up the count value Ca to “300”. Therefore, the light emission amount instruction circuit 400 sets the light emission amount instruction value Cb1 to “255”, Cb6 to “150”, Cb2 to “75”, Cb5 to “25”, and other light emission amount instruction values Cb3, Cb4 is set to “0”. Therefore, in the period in which writing is performed on the pixels in the 301st row in the liquid crystal display panel 100, the light source 31 in the first region is lit with 100% luminance, and the light source 36 in the sixth region is lit with 60% luminance. The light source 32 in the second region is turned on with a luminance of 30%, the light source 35 in the fifth region is turned on with a luminance of 10%, and the light sources 33 and 34 in other regions are turned off. This state continues until the video data Vd in the 400th row is supplied and the count value Ca becomes “399”.
When the video data Vd in the 401st row is supplied, the line counter 42 counts up the count value Ca to “400”. Therefore, the light emission amount instruction circuit 400 sets the light emission amount instruction value Cb2 to “255”, Cb6 to “50”, and other light emission amount instruction values Cb1, Cb3 to Cb5 to “0”. Therefore, in the period in which writing is performed on the pixels in the 401st row in the liquid crystal display panel 100, the light source 32 in the second region is lit with 100% luminance, and the light source 36 in the sixth region is lit with 20% luminance. The light sources 31 and 33 to 35 in other areas are turned off. This state continues until the video data Vd in the 500th row is supplied and the count value Ca reaches “499”.
When the video data Vd in the 501st row is supplied, the line counter 42 counts up the count value Ca to “500”. Therefore, the light emission amount instruction circuit 400 sets only the light emission amount instruction value Cb3 to “255” and sets the other light emission amount instruction values Cb1, Cb2, and Cb4 to Cb6 to “0”. Therefore, only the light source 33 in the third region is lit with 100% luminance during the period in which writing is performed on the pixels in the 501st row in the liquid crystal display panel 100, and the light sources 31, 32, 34 to 36 in the other regions are Turns off. This state continues until the video data Vd in the 600th row is supplied and the count value Ca reaches “599”.
Thereafter, the process proceeds to the next frame, and the count value Ca is reset to zero, so that the same operation is repeated.

FIG. 6 is a diagram showing the luminance transition of the light sources 31 to 36 in the relationship of scanning line selection, and the vertical axis represents the number of scanning lines. In FIG. 6, the white line is a diagram showing the temporal transition of the selected scanning line. Since the scanning lines are actually selected discretely in time such as the 1st, 2nd, 3rd,..., 600th row, the state in which the scanning line is selected is actually indicated by non-continuous dots. However, for the sake of brevity, in the figure, it is indicated by a continuous dot (white solid line) descending to the right.
FIG. 7 is a diagram showing such a temporal luminance transition in relation to the display area 101.

In particular, as shown in FIG. 6, the light sources 31 to 36 are at a timing after a predetermined time has elapsed since the corresponding scanning lines of the first to sixth regions are selected and before the next scanning line is selected. Lights up sequentially with 100% brightness. Since the electro-optical response speed of the pixel (liquid crystal element) is relatively low, a certain amount of time is required until the transmittance corresponding to the voltage is obtained after the voltage corresponding to the gradation is written. This is because the light source is turned on after a certain period of time has elapsed, and the state where the transmittance according to the written voltage is obtained is visually recognized.
Also, since the light sources other than the light source with 100% luminance are turned off or turned on in a relatively dark state of 60% or less, the moving image display characteristics can be improved by the so-called black insertion effect. It becomes.

By the way, in the configuration in which the light sources in the first to sixth regions are only turned on in order at a luminance of 100%, for example, the lighting region changes as shown on the left side of FIG. The actual luminance distribution changes as shown on the right side of FIG.
Since the luminance perceived by humans is indicated by the integrated value of the light quantity when the frame is taken as a unit period, when the six in-plane luminances are integrated, the first and sixth areas are the second to fifth areas. It will be dark compared. This is because of the following reason. Each of the second to fifth regions has different light sources on the upper and lower sides. For this reason, each of the second to fifth regions becomes brighter under the influence of light leakage when the light source in the upper region is turned on and when the light source in the lower region is turned on. On the other hand, in the first region located at the top, there is no light source on the upper side, so light leakage always occurs only when the light source in the lower region is always turned on. Similarly, since the light source does not exist below the sixth region located at the bottom, light leakage always occurs only when the light source in the upper region is always turned on.
Therefore, the first and sixth regions that are affected only by light leakage only when the adjacent region is lit on one side are the second to fifth regions that are affected by light leakage when both regions are lit. In comparison, it looks dark when the frame period is taken as a unit.
This is considered by the temporal change in luminance at the uppermost end, the center, and the lowermost end of the display area 101 as shown in FIG. The region emitting light with a luminance of 100% repeats the movement from the uppermost end to the lowermost end of the display region 101. At this time, at the center of the display area 101, before and after the timing when the luminance becomes 100%, the influence of light leakage is strongly influenced as the timing approaches. On the other hand, at the uppermost end, light leakage does not occur in principle before the timing when the luminance reaches 100%, and similarly, at the lowermost end, the principle occurs at the timing after the timing when the luminance becomes 100%. Light leakage does not occur.

In contrast, in the present embodiment, the light source 31 in the first region is lit at 60% luminance before the light source 36 in the sixth region is lit at 100% luminance before being lit at 100% luminance. I am letting. Thereby, in the 1st field, it becomes bright as if light leakage has occurred from the light source which should not exist in the upper part.
Similarly, the light source 36 in the sixth region is lit at 60% luminance when the light source 31 in the first region is lit at 100% luminance after being lit at 100% luminance. Thereby, in the sixth region, the light is bright as if light leaks from a light source that should not exist on the lower side.
For this reason, in this embodiment, it is suppressed that the 1st area | region located in the uppermost end and the 6th area | region located in the lowest end become dark compared with the 2nd-5th area | region. Further, as shown in FIG. 8, the luminance at the uppermost end, the center, and the lowermost end of the display area 101 also changes with similar characteristics in time, and the changing characteristics are also uniform, so that the brightness feeling is uniform. It is also possible to ensure the sex.

  Light leakage may occur not only when adjacent light sources are turned on, but also when light sources in two or more regions are turned on. For example, it is considered that the third region is not less bright due to light leakage even when the light source 31 of the first region separated on the upper side is turned on and when the light source 35 of the fifth region separated on the lower side is turned on. Similarly, it is considered that the fourth region becomes not less bright due to light leakage even when the light source 32 of the second region separated on the upper side is turned on and the light source 36 of the sixth region separated on the lower side is turned on. .

  On the other hand, in the second region, there is no region separated by two upwards. Even in the fifth region, there is no region that is two lower apart. For this reason, the second and fifth regions are not affected by light leakage as long as there are no two regions above or below, so the light leakage from two regions above and below is less affected. It becomes darker than the third and fourth regions to receive. In the first area, there is no area that is two places away from the upper side, and in the sixth area, there is no area that is two places away from the lower side.

Therefore, in the present embodiment, the light source 31 in the first region is turned on at a luminance of 20% when the light source 35 in the fifth region is turned on at a luminance of 100%, and the light source 32 in the second region is a sixth light source. When the light source 36 in the area is turned on at a luminance of 100%, the light source 36 is turned on at a luminance of 10%. Thereby, in the first region and the second region, the light source is supposed to be slightly brighter as if light leakage has occurred from the light source that should not exist two distances on the upper side.
Similarly, the light source 36 in the sixth region is turned on at a luminance of 20% when the light source 32 in the second region is turned on at a luminance of 100%, and the light source 31 in the first region is turned on for the light source 35 in the fifth region. Is turned on at a luminance of 10%. Thereby, in the 6th field and the 1st field, it will become bright a little as if light leakage has occurred from the light source which should not exist two apart on the lower side.
Thereby, in this embodiment, the phenomenon which becomes dark gradually as it goes to the upper and lower ends from the center of the screen is eliminated, and it becomes possible to ensure uniform brightness of the screen.
In the present embodiment, “25” (luminance 10%), “50” (luminance 20%), “75” (luminance 30%), and “150” (luminance 60%) are indicated as follows. This is an example, and is determined in consideration of the actual degree of light leakage.

As described above, according to the present embodiment, even when the light emitting area is divided from the first area to the sixth area and each area is sequentially turned on with 100% luminance, the brightness of the screen is made uniform. It becomes possible.
By the way, if the backlight 30 is configured so that no light leakage occurs, the brightness of the screen can be made uniform. However, such a configuration requires not only that the partition walls and the like in the backlight 30 are made with high accuracy, but also that the backlight 30 must be accurately positioned and attached to the liquid crystal display panel 100. It can be said that it is difficult. In particular, in a portable information terminal, the display area of the liquid crystal display panel is also small, which makes it extremely difficult.
In the present embodiment, since the brightness in each region is made uniform by artificially generating light leakage, compared with a configuration in which light leakage does not occur in the backlight, It is easy to make the brightness uniform.

In the embodiment, N is described as “6”, but may be “7” or more, or may be “3”, “4”, and “5”.
In the embodiment, the light leakage from the adjacent region and the two separated regions is considered. However, if the light leakage from the separated region is small enough to be ignored, the light leakage from only the adjacent region is considered. You may do it. Further, when the degree of light leakage is large, light leakage due to a region further away by 3 or more may be considered. Note that “N” is an integer equal to or greater than 5 when light leakage due to a region separated by 3 or greater is considered.
Furthermore, in the embodiment, the vertical blanking period is described as zero, but it is needless to say that the vertical blanking period may be considered.
In the embodiment, the white LED is used as the light source. However, any device that changes the luminance may be used. Although the liquid crystal display panel has been described as a transmissive type, the present invention can also be applied to a case where a so-called transflective type is used in a transmissive mode.

Next, an electronic apparatus having the liquid crystal display device 1 according to the above-described embodiment will be described. FIG. 9 is a diagram illustrating a configuration of a mobile phone 1200 using the liquid crystal display device 1 according to the embodiment.
As shown in this figure, the cellular phone 1200 includes the above-described liquid crystal display device in addition to a plurality of operation buttons 1202 as well as an earpiece 1204 and a mouthpiece 1206. Of the liquid crystal display devices, only the liquid crystal display panel 100 appears as an external appearance, and the others are in the casing of the mobile phone.
Note that the liquid crystal display device according to the embodiment is also applicable to electronic devices other than mobile phones. Examples of such electronic devices include digital still cameras, laptop computers, liquid crystal televisions, viewfinder type (or monitor direct view type) video recorders, car navigation devices, electronic notebooks, calculators, word processors, workstations, videophones, The thing which has display parts, such as equipment provided with a touch panel, is mentioned.

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display device, 20 ... Display control circuit, 30 ... Back light, 31-36 ... Light source, 40 ... Light source drive circuit, 100 ... Liquid crystal display panel, 130 ... Y driver, 140 ... X driver, 1200 ... Mobile phone

Claims (7)

The display area of the liquid crystal display panel is divided along one direction and provided corresponding to each of a plurality of areas arranged side by side in the other direction, and light is transmitted from the back side of the liquid crystal display panel to each of the areas. A plurality of light sources for irradiation;
Each of the plurality of light sources is turned on with a first luminance at a predetermined timing in a predetermined order,
Among the plurality of light sources, the light source located at the end in the arrangement of the regions is lit at a second luminance lower than the first luminance at a timing before or after the timing at which the light source is lit at the first luminance. A light source driving circuit
A backlight for a liquid crystal display panel, comprising: The one direction is an extending direction of a scanning line of the liquid crystal display panel,
The other direction is an extending direction of data lines of the liquid crystal display panel,
The first area is divided into the Nth area (N is an integer of 3 or more),
The light source driving circuit includes:
When turning on the first luminance from the light source of the first region to the light source of the Nth region in order,
The light source of the first region is lit at the second luminance at a timing before the timing at which the light source is lit at the first luminance,
The backlight according to claim 1, wherein the light source in the Nth region is turned on at the second luminance at a timing later than the timing at which the light source is turned on at the first luminance. When N is an integer of 5 or more,
The light source driving circuit includes:
The light source of the first region is lit darker than the second luminance at a timing prior to the timing of lighting the second luminance,
3. The backlight according to claim 2, wherein the light source of the Nth region is lit darker than the second luminance at a timing prior to the timing of lighting at the second luminance. When N is an integer of 5 or more,
The light source driving circuit includes:
The light source of the second region is lit darker than the second luminance at a timing prior to the timing of lighting at the first luminance,
3. The backlight according to claim 2, wherein the light source of the (N−1) -th region is lit darker than the second luminance at a timing before the timing of lighting at the first luminance. The display area of the liquid crystal display panel is divided along one direction and provided corresponding to each of a plurality of areas arranged side by side in the other direction, and light is transmitted from the back side of the liquid crystal display panel to each of the areas. A method of controlling a backlight having a plurality of light sources for irradiation,
A plurality of the light sources are respectively turned on with a first luminance at a predetermined timing in a predetermined order,
Among the plurality of light sources, the light source located at the end in the arrangement of the regions is lit at a second luminance lower than the first luminance at a timing before or after the timing at which the light source is lit at the first luminance. A method for controlling a backlight, characterized in that Having pixels provided corresponding to the intersections of a plurality of scanning lines and a plurality of data lines;
A liquid crystal display panel that selects a plurality of scanning lines in a predetermined order and writes a data signal to a pixel corresponding to the selected scanning line;
A backlight provided on the back side of the liquid crystal display panel for irradiating the liquid crystal display panel with light;
With
The backlight is
In the liquid crystal display panel, a display area in which the pixels are arranged is divided along the extending direction of the scanning lines and provided corresponding to each of a plurality of areas arranged in parallel in the extending direction of the data lines. Multiple light sources,
Each of the plurality of light sources is turned on with a first luminance at a timing when a predetermined time has elapsed with respect to the selection timing of the scanning line, and
Among the plurality of light sources, the light source located at the end in the arrangement of the regions is lit at a second luminance lower than the first luminance at a timing before or after the timing at which the light source is lit at the first luminance. A light source driving circuit
A liquid crystal display device comprising:   An electronic apparatus comprising the liquid crystal display device according to claim 6.

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