JP2009003270A - Liquid crystal display device and driving method of liquid crystal display device - Google Patents

Abstract

When a backlight is divided into twice the conventional size to prevent flickering of the display screen of a liquid crystal display panel, the circuit scale for controlling the LED of the light source is doubled.
A liquid crystal display panel and a backlight having a plurality of backlight blocks 150a, 150b and the like for illuminating the liquid crystal display panel with light emitted from light sources such as LEDs 2a ', 2k', 2b ', 2l', etc. Among the plurality of backlight blocks, at least two adjacent backlight blocks 150a and 150b, backlight blocks 150c and 150d, backlight blocks 150e and 150f, backlight blocks 150g and 150h, and backlight blocks 150i and 150j, respectively A PWM signal generation circuit 191 and switching transistors Tr1 to Tr5 that perform control of turning on at the same time and repeating the operation of turning on and off are provided.
[Selection] Figure 4

Description

  The present invention relates to a liquid crystal display device having a backlight divided into a plurality of backlight blocks, and a method for driving the liquid crystal display device.

  Liquid crystal display devices are thin and lightweight, and their use has been expanded in recent years as an alternative to conventional cathode ray tubes. However, currently widely used TN (Twisted Nematic) alignment liquid crystal display panels have a narrow viewing angle, a slow response speed, and appear to have a tail when moving images are displayed.

  On the other hand, in recent years, a liquid crystal display device including an OCB (Optically Compensated Birefringence) mode liquid crystal display element having characteristics of a high-speed response and a high viewing angle has been used. In this liquid crystal display device, a liquid crystal is bent to perform visual compensation, and an optical phase compensation film is combined with this to obtain a wide viewing angle.

  FIG. 10 is a cross-sectional view schematically showing an alignment state of liquid crystal molecules included in the OCB mode liquid crystal display element. 10A and 10B are cross-sectional views showing a voltage application state, and FIG. 10C is a cross-sectional view showing a voltage non-application state.

  Between the glass substrate 61 of the liquid crystal display panel which comprises the liquid crystal display device using the liquid crystal display element of OCB mode, as a liquid crystal molecule 62 in FIG.10 (a), FIG.10 (b), and FIG.10 (c). As shown, nematic liquid crystal is injected. The alignment state of the liquid crystal to which no voltage is applied is called a splay state 63.

  When a power supply of a liquid crystal display device using an OCB mode liquid crystal display element is turned on, it is necessary to perform driving called transfer driving. That is, the transfer driving means that a relatively large voltage of about 20 to 25 volts is applied to the liquid crystal layer when the liquid crystal display device is turned on, so that the splay state 63 shown in FIG. ), And the driving to shift to the bend states 64a and 64b shown in FIG. The display using the bend states 64a and 64b is a feature of the liquid crystal display device using the OCB mode liquid crystal display element. By changing the bend state according to the voltage, the transmittance of the panel can be increased. It is something to change.

  A bend state 64a shown in FIG. 10 (a) indicates a bend state when white is displayed, and a bend state 64b shown in FIG. 10 (b) indicates a bend state when black is displayed. .

  Further, in a liquid crystal display device using an OCB mode liquid crystal display element, when a voltage of 2 volts or less is continuously applied to the liquid crystal display panel, the alignment state of the liquid crystal gradually changes from the bend states 64a and 64b to the splay state 63. (Hereinafter, this transition is called reverse transition). In order to prevent such reverse transition, in a liquid crystal display device using an OCB mode liquid crystal display element, driving called reverse transition prevention driving is performed.

  That is, in the case of a normally white mode liquid crystal display device that performs white display when a relatively low voltage is applied and performs black display when a relatively high voltage is applied, reverse transition prevention drive is In this drive, reverse transition is prevented by applying a voltage corresponding to black separately from the video signal periodically displayed on each pixel.

  The reverse transition prevention drive is called double-speed conversion in which an operation of applying a voltage corresponding to black to the pixel and an operation of applying a voltage corresponding to the video signal to the pixel are alternately performed to prevent reverse transition. There is a reverse transition prevention drive (see, for example, Patent Document 1). Hereinafter, this double speed conversion is referred to as black insertion driving.

  Therefore, in a conventional liquid crystal display device using an OCB mode liquid crystal display element, a voltage corresponding to a video signal is applied to a pixel during a period in which one frame (or one field) image is displayed. In order to prevent reverse transition, a black insertion period in which a voltage corresponding to black is applied to the pixel is provided.

  By using the black insertion driving described above, the display of the liquid crystal display device using the OCB mode liquid crystal display element can be brought close to an impulse type display such as a CRT. This is because the high-speed response that is an advantage of the OCB mode liquid crystal display element can be used. By using the black insertion drive, it is possible to improve the visibility of the moving image and display a high contrast.

  Note that in the liquid crystal display panels other than the OCB mode, such as a TN (Twisted Nematic) alignment liquid crystal display panel that is widely used at present, the double speed conversion described above may be used in order to improve moving image visibility. The driving of the liquid crystal display device in such a case is also referred to as black insertion driving.

  Furthermore, in recent years, with the spread of backlights using LEDs and the improvement in the high-speed response of cold cathode fluorescent lamps, backlights that drive the backlights in conjunction with driving of the liquid crystal display panel by a source driver or the like have been developed. Drive systems are also being implemented (see, for example, Patent Document 2).

  A conventional liquid crystal display device that performs such a backlight driving method will be described below.

  FIG. 11 is a block diagram of a conventional liquid crystal display device 101 that performs black insertion driving and drives a backlight in conjunction with driving of a liquid crystal display panel by a source driver or the like.

  The liquid crystal display device 101 includes a liquid crystal display panel 10, a backlight 11, a source driver 2, a gate driver 3, a controller 4, a frame memory 22, a liquid crystal driving voltage generation circuit 17, and a backlight control unit 19.

  The liquid crystal display panel 10 is an active matrix liquid crystal display panel. That is, in the liquid crystal display panel 10, signal lines and scanning lines are arranged in a matrix on an array substrate, and switching elements and pixel electrodes are formed at their intersections. A liquid crystal layer is sandwiched between the formed counter substrate. An OCB mode liquid crystal is used as the liquid crystal layer. In addition, red, green, and blue color filters are provided on the counter substrate of the liquid crystal display panel 10.

  The backlight 11 is disposed on the back surface of the liquid crystal display panel 10 and is divided into a plurality of backlight blocks, and each backlight block is provided with an LED as a light source and a light guide plate.

  Here, the configuration of the backlight 11 of the conventional liquid crystal display device 101 will be described with reference to schematic diagrams shown in FIGS. 12 (a) and 12 (b).

  12A is a plan view of the backlight 11 viewed from a direction orthogonal to the display surface of the liquid crystal display panel 10, and FIG. 12B is a cross-sectional view of the backlight 11 taken along lines A and A ′.

  As shown in FIGS. 12A and 12B, the backlight 11 is divided into a plurality of backlight blocks 15a to 15e. Then, at the both ends of each of the plurality of backlight blocks 15a to 15e, two right and left LEDs 2a and 2b and LEDs 2k and 2l, LEDs 2c and 2d and LEDs 2m and 2n, LEDs 2e and 2f and LEDs 2o and 2p, LEDs 2g and 2h and LEDs 2q and 2r, and LEDs 2i and 2j and LEDs 2s and 2t are arranged, respectively.

  In addition, light guide plates 12a to 12e are further arranged in the backlight blocks 15a to 15e, respectively. In addition, the boundary surfaces 12ab, 12bc, 12cd, and 12de of the adjacent light guide plates are configured to be capable of reducing light leakage to the adjacent light guide plate side by, for example, mirror finishing.

  Each of the backlight blocks 15a to 15e mainly illuminates the portion of the display area of the liquid crystal display panel 10 that the backlight block faces. In addition, the color of the light which LED2a-2j and LED2k-2t which are the light sources of the backlight 11 inject | emit are white.

  The liquid crystal drive voltage generation circuit 17 is a circuit that adjusts the voltage supplied to the source driver 2 and the gate driver 3.

  The gate driver 3 is a circuit that supplies a gate signal to the scanning lines of the liquid crystal display panel 10.

  The source driver 2 is a circuit that supplies a voltage corresponding to a display signal during a display period and supplies a voltage corresponding to black to a signal line of the liquid crystal display panel 10 during a black insertion period.

  The controller 4 includes a signal processing unit 21 and a timing control unit 23, and the source driver 2 includes a D / A conversion unit 24 and a shift register 25.

  The timing control unit 23 controls the timing at which the gate driver 3 is operated and the timing at which the image signal is sent to the source driver 2, and the backlight 11 is turned on and off in conjunction with the driving of the liquid crystal display panel 10 by the source driver 2 and the like. This is a circuit for sending a backlight control signal, which is a signal for causing the backlight control unit 19, to the backlight control unit 19.

  The backlight control unit 19 controls turning on / off of the backlight 11 in accordance with a backlight control signal sent from the timing control unit 23.

  The frame memory 22 is a memory for storing a video signal for one screen.

  Next, the operation of the conventional liquid crystal display device 101 will be described mainly focusing on the control of the backlight 11.

  When the power of the liquid crystal display device 101 is turned on, the liquid crystal layer of the liquid crystal display panel 10 remains in the splay state 63 as shown in FIG. 10C, so that the bend state 64a in FIG. It is also necessary to shift to the bend state 64b of FIG.

  Therefore, when the power of the liquid crystal display device 101 is turned on, the liquid crystal display device 101 performs transition driving in order to transition the liquid crystal layer from the splay state to the bend state. That is, the source driver 2 uses the voltage for transfer driving so that the voltage between the pixel electrode and the counter electrode is higher than the voltage for displaying an image of 20 to 25 volts for a predetermined time. As a result, a voltage of 20 to 25 volts is applied to the signal line. Accordingly, a voltage for driving the transition is applied to the liquid crystal layer for a predetermined time, so that the liquid crystal layer of the liquid crystal display panel 10 transitions from the splay state to the bend state, and the display operation of the liquid crystal display device 101 is possible. It becomes.

  When the transfer driving is completed as described above and the display operation is enabled, the liquid crystal display device 101 starts the display operation.

  When the liquid crystal display device 101 performs a display operation, the timing control unit 23 of the controller 4 sends a control signal to the gate driver 3 and the source driver 2 in accordance with a video signal input from the outside. As a result, the gate driver 3 applies a scanning signal voltage to each scanning line to sequentially turn on the switching elements of each pixel.

  During the display period, the source driver 2 applies a voltage corresponding to the video signal to each signal line in accordance with the timing when the gate driver 3 applies the scanning signal voltage to each scanning line, and applies the video signal to each pixel. The corresponding voltage is written. As a result, an image corresponding to the video signal is displayed on the liquid crystal display panel 10.

  Further, during the black insertion period, the source driver 2 applies a voltage corresponding to black to each signal line in accordance with the timing when the gate driver 3 applies the scanning signal voltage to each scanning line, and turns black to each pixel. The corresponding voltage is written. As a result, a black image is displayed on the liquid crystal display panel 10.

  Further, the timing control unit 23 supplies a backlight control signal, which is a signal for interlocking with the driving of the liquid crystal display panel 10 by the source driver 2 and the like, to the backlight control unit 19.

  The backlight control unit 19 controls turning on / off of each of the backlight blocks 15a to 15e based on the backlight control signal sent from the timing control unit 23.

  That is, the backlight control unit 19 turns on the backlight at the same time that the voltage corresponding to the video signal starts to be written to the pixel in the display screen area facing the backlight block 15a in the display screen of the liquid crystal display panel 10. To do.

  The backlight control unit 19 performs the same control on the backlight blocks 15b to 15e. The control performed by the backlight control unit 19 will be described in more detail below with reference to FIG.

  FIG. 13 shows an example of a timing chart of gate pulses and lighting / extinguishing of the backlight blocks 15a to 15e at the time of black insertion driving in the liquid crystal display device 101 shown in FIG. In FIG. 13, time elapses from the left side to the right side as viewed in the drawing. That is, the left side of the page is the past and the right side is the future.

  The uppermost timing chart in FIG. 13 shows a vertical synchronization signal that is one of the backlight control signals output from the timing control unit 23.

  Reference numerals G1 to G20 in FIG. 13 are reference numerals used to distinguish the scanning lines, and the right side of the reference numerals indicates the timing of the gate signals output from the gate driver 3 to the respective scanning lines G1 to G20. In addition, on the right side of the display of the backlight blocks 15a to 15e in FIG. 13, the timing of the signals indicating the luminance of the backlight blocks 15a to 15e is shown. Show.

  As shown in FIG. 13, the pixel columns corresponding to the scanning lines G1 to G4 are opposed to the backlight block 15a, and the pixel columns corresponding to the scanning lines G5 to G8 are opposed to the backlight block 15b. Pixel columns corresponding to the lines G9 to G12 face the backlight block 15c, pixel rows corresponding to the scanning lines G13 to G16 face the backlight block 15d, and pixels corresponding to the scanning lines G17 to G20 The row faces the backlight block 15e.

  In FIG. 13, the number of scanning lines G1 to G20 is 20 for easy understanding, but there are actually a large number of scanning lines. For example, when 1280 pixels are arranged in the horizontal direction and 1024 pixels are arranged in the vertical direction on the display screen of the liquid crystal display panel 10, there are 1024 scanning lines. .

  In FIG. 13, the symbol shown on the right side of the time when each gate signal goes high indicates the type of voltage written to the pixel at the time when each gate signal goes high. A case where a voltage corresponding to display data is written to the pixel is indicated by S, and a case where a voltage corresponding to black for black insertion is written to the pixel is indicated by B.

  For the scanning line G1, the gate signal of the scanning line G1 becomes high in accordance with the timing at which the voltage corresponding to the display data is output from the source driver 2, and each pixel on the scanning line G1 corresponds to the display data. The voltage to be written is written. Next, the gate signal of the scanning line G1 becomes high again at the timing when the voltage corresponding to black for black insertion is output from the source driver 2, and the black signal is inserted into each pixel on the scanning line G1. The voltage corresponding to the black color is written.

  For the scanning line G2, the gate signal of the scanning line G2 becomes high after a predetermined time delay with respect to the timing when the gate signal of the scanning line G1 becomes high, and display data or black is inserted in accordance with the timing. For this reason, a voltage corresponding to black is written to each pixel existing on the scanning line G2.

  Similarly, display data or black insertion data is written to each pixel existing on the scanning line in accordance with the timing when the gate signal of each scanning line becomes high.

  As described above, each scanning line G1 to G20 is selected twice in one frame period (or one field period), and a voltage corresponding to the display data and black color are applied to the pixels on each scanning line G1 to G20. The voltage corresponding to the insertion data is written once. Therefore, it is possible to realize the black insertion driving for writing the black insertion data periodically while writing the display data.

  On the other hand, according to the backlight control signal supplied from the timing control unit 23, the backlight control unit 19 controls the lighting of the backlight blocks 15a to 15e so as to be linked to the above-described black insertion driving.

  As described with reference to FIG. 13, as time elapses, the liquid crystal display device 101 displays display signals from the top to the bottom of the display screen of the liquid crystal display panel 10 in one frame period (or one field period). Thereafter, black for black insertion is displayed from the top to the bottom of the display screen.

  As shown in FIG. 13, at the timing T1, the vertical synchronization signal, which is also the backlight control signal, is set to the high state from the timing control unit 23, and one frame period (or one field period) is started.

  After the time T1, the backlight control unit 19 turns on only the backlight block 15a that mainly illuminates each pixel column corresponding to the scanning lines G1 to G4 during the period up to the time T2, and the backlight block 15b. ˜15e is turned off.

  Since the voltage corresponding to black for black insertion is sequentially written in each pixel column corresponding to the scanning lines G1 to G4 after the time T2 has passed and until the time T3, the backlight control unit 19 Then, the backlight block 15a is turned off. Then, the backlight control unit 19 turns on the backlight block 15b that mainly illuminates each pixel column corresponding to the scanning lines G5 to G8, and turns off the backlight blocks 15c to 15e.

  Hereinafter, similarly, the backlight control unit 19 controls the backlight blocks 15a to 15e so that the backlight blocks 15a to 15e are sequentially turned on.

  In addition, after the time T6 has elapsed, the backlight control unit 19 causes the backlight block 15a to turn off all the backlight blocks 15a to 15e at the time until the start time T1 of the next frame period (or field period). Control ~ 15e.

  The backlight control unit 19 repeats the above control every frame period (or one field period). In this way, the backlight control unit 19 controls the lighting of the backlight blocks 15a to 15e in accordance with the black insertion driving according to the backlight control signal supplied from the timing control unit 23.

  In this way, the backlight control unit 19 divides the backlight 11 into a plurality of backlight blocks 15a to 15e and turns on and off the backlight blocks 15a to 15e in conjunction with the black insertion driving described above. The timing of turning on / off the blocks 15a to 15e is controlled. That is, when a voltage corresponding to black for black insertion is written to a pixel, the backlight block corresponding to that portion is turned off.

Thereby, the moving image visibility of the liquid crystal display device 101 can be improved, and high contrast and low power consumption can also be realized.
JP 2003-280617 A JP-A-11-297485

  However, in the conventional liquid crystal display device 101, the backlight 11 is divided into backlight blocks 15a to 15e as shown in FIG. 12, and the light guide plate is also divided like the light guide plates 12a to 12e. For this reason, a streak-like shadow part may be seen in the part corresponding to the level | step-difference part of boundary surface 12ab, 12bc, 12cd, 12de of each light-guide plate 12a-12e of the display screen of the liquid crystal display panel 10. FIG.

  The reason for the occurrence of the streaky shadow will be described in more detail.

  In order to suppress a color shift of the display screen of the liquid crystal display panel 10 due to variations in the LEDs 2a to 2j and LEDs 2k to 2t that are light sources, the backlight blocks 15a to 15e are light sources to the other adjacent backlight blocks 15a to 15e. The LEDs 2a to 2j and the LEDs 2k to 2t are intentionally leaked by a predetermined amount.

  For example, when the backlight block 15a is turned on and all the backlight blocks 15b to 15e are turned off, the luminance of the portion corresponding to the backlight block 15a on the display screen of the liquid crystal display panel 10 (however, The brightness of the portion corresponding to the adjacent backlight block 15b is the result of light leaking from the lighted block. Assume that the luminance is about 30%.

  When the light guide plates 12a to 12e are configured to simply contact at the boundary, a slight level difference occurs between the light guide plates on the display screen side. The light emitted from the LEDs 13a and 14a of the backlight block 15a propagates through the light guide plate 12a and is irregularly reflected at the boundary between the light guide plate 12a and the light guide plate 12b. Thereby, light leaks to the adjacent backlight block 15b side.

  As a result, when the backlight block 15a is turned on and the backlight block 15b is turned off, the streaks described above are formed on the light guide plate 12b side along the stepped portion of the boundary between the light guide plate 12a and the light guide plate 12b. The shadow of

  Beads are scattered on the boundaries of the light guide plates 12a to 12e, and an air layer is provided, or a partition is formed on the boundaries of the light guide plates 12a to 12e, or the upper corners of the light guide plates are rounded. The streaky shadow portion described above also occurs when the image is present.

  Then, as the backlight blocks 15a to 15e are sequentially switched on and off as shown in FIG. 13, the streaky shadows move on the display screen of the liquid crystal display panel 10 and flicker like flickering to the user. It will be recognized.

  FIG. 14A and FIG. 14B show such shadow portions. FIG. 14A shows a turn-on / off pattern from the time T1 in FIG. 13 until the time T2 is reached. FIG. 14B shows a lighting / light-off pattern from the time T2 in FIG. 13 until the time T3 is reached.

  14A, the backlight block 15b side along the boundary between the light guide plate 12a of the backlight block 15a and the light guide plate 12b of the backlight block 15b in the display screen of the liquid crystal display panel 10. A streak-shaped shadow portion 16b is generated in the portion.

  14B, the backlight block 15a is aligned along the boundary between the light guide plate 12a of the backlight block 15a and the light guide plate 12b of the backlight block 15b in the display screen of the liquid crystal display panel 10. A streak-shaped shadow portion 16a is formed in the portion on the left side. Similarly, a streak-shaped shadow portion 17c is generated at a portion on the backlight block 15c side.

  Then, immediately before reaching time T2 in FIG. 13, the shadow portion 16b occurs on the backlight block 15b side as shown in FIG. 14A, and when the time T2 has passed, the shadow portion 16b instantly. However, as shown in FIG. 14B, it moves to the backlight block 15a side to become a shadow portion 16a.

  Similarly, a shadow is generated at each boundary of the backlight blocks 15b to 15e, and the boundary is instantaneously moved when the shadow is switched from lighting to extinguishing.

  Thus, when displaying an image on the display screen of the liquid crystal display panel 10, the backlight blocks 15a to 15e are switched on and off instantaneously as shown in FIG. Shadow portions generated on portions of the screen corresponding to the boundary surfaces of the backlight blocks 15a to 15e move instantaneously. Therefore, the display screen of the liquid crystal display panel 10 appears to flicker like a flicker to the user.

  Therefore, in order to reduce the streak-like shadow portion generated on such a boundary surface, for example, it may be configured to increase the amount of light leakage between the backlight blocks.

  However, if the amount of light leakage between the backlight blocks is increased so that the luminance of about 30% is generated as described above, for example, about 50% of luminance is generated, the contrast and the response of moving images are increased. There is a problem in that the use of the black insertion drive causes a decrease, and the moving image visibility is improved and the original purpose of displaying a high contrast is not achieved.

  Therefore, in order to solve such problems, it is assumed that the amount of light leakage between the backlight blocks is set to a luminance level of 50% in terms of luminance level, and the number of divisions of the backlight. Is doubled, the density of streaky shadows formed on the boundary surface of the backlight block is reduced, making it less noticeable, and it is possible to improve contrast and video response. Thought.

  However, since the number of backlight blocks is doubled, the circuit scale for controlling ON / OFF of the LED as the light source is doubled, resulting in a problem of increasing costs. Noticed.

  In order to solve the above-mentioned problems that the present inventors have noticed, the present invention, even when the backlight is divided into a larger number of backlight blocks than before, without increasing the control circuit scale of the light source, An object of the present invention is to provide a liquid crystal display device capable of suppressing flickering visible on a display screen of a liquid crystal display panel as compared with the conventional one and improving contrast and moving image response, and a driving method of the liquid crystal display device It is.

In order to solve the above-described problems, a first aspect of the present invention includes a liquid crystal display panel,
A backlight having a plurality of backlight blocks in which a light source is disposed and illuminates the liquid crystal display panel with light emitted from the light source;
A backlight control unit that performs control to sequentially turn on and off the light at least two backlight blocks adjacent to each other among the plurality of backlight blocks;
Is a liquid crystal display device.

  Further, according to the second aspect of the present invention, the plurality of backlight blocks may be reduced to a predetermined luminance level at a higher ratio as a result of leakage light between adjacent backlight blocks. Further, in the liquid crystal display device according to the first aspect of the present invention, a boundary surface between the backlight blocks is adjusted.

  Further, according to a third aspect of the present invention, in the above control, the number of backlight blocks that are turned on at the same time and the number of backlight blocks that are turned off at the same time are the same. 2 is a liquid crystal display device of the present invention.

  According to a fourth aspect of the present invention, in the above control, the number of backlight blocks that are lit simultaneously is greater than the number of backlight blocks that are simultaneously turned off among the lit backlight blocks. 2 is a liquid crystal display device of the present invention.

According to a fifth aspect of the present invention, of the display period and the black insertion period provided within one field or one frame period, (1) a voltage corresponding to black data is applied to the black insertion period. (2) a source driver for performing black insertion driving for supplying a voltage corresponding to display data to the signal line of the liquid crystal display panel in the display period;
The backlight control unit is configured to turn off the backlight block when the state of the display area of the liquid crystal display panel facing the backlight block is the black insertion period. It is a liquid crystal display device of the invention.

  The sixth aspect of the present invention is the liquid crystal display device according to the fifth aspect of the present invention, wherein an OCB liquid crystal is used for the liquid crystal display panel.

According to a seventh aspect of the present invention, there is provided a backlight having a liquid crystal display panel and a light source, the backlight having a plurality of backlight blocks that illuminate the liquid crystal display panel with light emitted from the light source, and the backlight. A method of driving a liquid crystal display device including a backlight control unit that controls lighting and turning off of a block,
In the liquid crystal display device driving method, the control unit performs control to turn on at least two adjacent backlight blocks of the plurality of backlight blocks at the same time and sequentially repeat the turning on and off operations.

  In the present invention, even when the backlight is divided into a larger number of backlight blocks than in the past, the flicker visible on the display screen of the liquid crystal display panel is increased compared with the conventional one without increasing the control circuit scale of the light source. It can be suppressed, and the effect of improving the contrast and moving image responsiveness is exhibited.

Embodiments of the present invention will be described below with reference to the drawings.
(Embodiment 1)
The configuration of an embodiment of the liquid crystal display device of the present invention will be described first with reference mainly to FIGS.

  FIG. 1 is a block diagram of a liquid crystal display device 1 as an example of a liquid crystal display device according to the present invention.

  A liquid crystal display device 1 shown in FIG. 1 is a device that performs black insertion driving and drives a backlight in conjunction with driving of a liquid crystal display panel, as with the liquid crystal display device 101 described in the background art, and will be described later. Since the configuration is basically the same as in FIG. 11 except for the backlight 110 and the backlight control unit 190, the same components are denoted by the same reference numerals, and the liquid crystal display according to the present embodiment is mainly focused on the differences. The configuration of the device 1 will be described.

  Note that the liquid crystal display device 1 of the present embodiment is described as a liquid crystal display device using an OCB mode liquid crystal display element in the same manner as the liquid crystal display device 101 described in the background art, and black insertion driving is also performed in the background art. In the following description, it is assumed that the driving is similar to the black insertion driving described above. Further, black insertion driving in a liquid crystal display panel other than the OCB mode, such as a TN (twisted nematic) alignment liquid crystal display panel, will be described later.

  FIG. 2 is a schematic configuration diagram of the backlight 110 of the liquid crystal display device 1 of the present invention.

  2A is a plan view of the backlight 110, and FIG. 2B is a cross-sectional view of the backlight block 110 taken along the line A-A ′.

  2, the same components as those in FIG. 12 are denoted by the same reference numerals, and the description thereof is omitted. Differences between the backlight 110 of the present embodiment and the backlight 11 of FIG. 12 are as follows.

  As shown in FIG. 2, the backlight 110 of the present embodiment is divided into ten backlight blocks 150a to 150j, and each backlight block has one LED 2a for light source, one at each end. 'And 2k', LEDs 2b 'and 2l', ... LEDs 2j 'and 2t' are arranged. In addition, light guide plates 120a to 120j are further arranged in each of the ten divided backlight blocks 150a to 150j.

  Also, as shown in FIG. 3, for example, assuming that the ideal luminance of the backlight blocks 150e and 150f is 100 (when light leakage is 0), the maximum amount of light leaking to the adjacent backlight blocks 150d and 150g is By adjusting the maximum value to 50, the luminance of the backlight block to be lit can be secured at least 50. Since such light leakage (max 50) can be estimated to spread evenly to adjacent backlight blocks, the light leakage to each adjacent backlight block is approximately max 25 on one side. Therefore, when compared with the luminance (min50) of the backlight block to be lit in a light leaking state as a reference, it can be said that the luminance (max25) of each adjacent backlight block is approximately half of that.

  Therefore, when the above description is applied to each of the boundary surfaces 112ab to 112ij (see FIG. 2) of each backlight block shown in FIG. 3, the result is that the luminance is lower due to leakage light between the adjacent backlight blocks. With a higher value as a reference, the luminance level is approximately ½ of that.

  The adjustment of the leakage light is not limited to this, and for example, it can be adjusted by the surface roughness of the boundary surface between the backlight blocks formed by dividing the light guide plate. That is, the rougher the surface roughness, the greater the amount of leaked light, and the closer to the mirror finish, the less leaked light. There is also a method of blocking leakage light by providing a gap between adjacent light guide plates.

  FIG. 3 is a diagram showing the luminance level of each backlight block in a situation where the central backlight blocks 150e and 150f are turned on simultaneously and all the other backlight blocks are turned off.

  As shown in FIG. 3, the backlight blocks 150d and 150g on both sides of the central backlight block (assuming that the luminance level is c) are turned off, but leakage from the lit backlight blocks 150e and 150f is turned off. As a result, the luminance level c / 2 is obtained by light, and the luminance levels of the backlight blocks 150a and 150i at both ends are c / 16.

  As described above, the configuration in which the leakage light is increased makes it difficult to see the shadow portion generated on the display screen of the liquid crystal display panel as compared with the conventional case, and even if the flicker visible on the display screen can be suppressed as compared with the conventional case, the contrast and The reason why the moving image response is not lowered will be described later with reference to FIG.

  As shown in FIG. 4, the backlight control unit 190 of the present embodiment obtains a vertical synchronization signal from the timing control unit 23, and two adjacent backlight blocks 150a and 150b, 150c and 150d,. ... Includes a PWM signal generation circuit 191 and switching transistors Tr1 to Tr5 for supplying a control signal for sequentially turning on and off 150i and 150j to the backlight 110.

  FIG. 4 is a diagram showing a specific circuit configuration of the backlight control unit 190 and the connection relationship of LEDs in each backlight block. At the same time, in FIG. 4, a pulse signal output from the PWM signal generation circuit 191 Is schematically shown. In addition, in the same figure, each LED was enclosed with the broken line for every backlight block in which they are arrange | positioned, and the code | symbol of the corresponding backlight block was attached | subjected.

  As shown in FIG. 4, the LEDs arranged in the backlight block are connected in series between the power supply voltage line 192 and each of the switching transistors Tr1 to Tr5, each of the four LEDs provided in two adjacent blocks. Has been. The pulse signals S1 to S5 are input from the PWM signal generation circuit 191 to the gate lines GL1 to GL5 of the switching transistors Tr1 to Tr5. The pulse signals S1 to S5 are signals for controlling the ON / OFF timing of the switching transistors Tr1 to Tr5, and the signals shown with backlight blocks 15a to 15e in the timing chart of FIG. This is basically the same except for the differences described later.

  With the above configuration, the operation of the backlight 110 and the backlight control unit 190 of the liquid crystal display device of the present embodiment will be described with reference to FIGS. 1, 4, 5, and 13. At the same time, an embodiment of the driving method of the liquid crystal display device of the present invention will be described at the same time.

  The circuit configuration shown in FIG. 4 of the present embodiment is basically the same as the circuit configuration of corresponding portions in the liquid crystal display device 101 having the conventional backlight 11 shown in FIG. Therefore, the conventional operation description shown in FIG. 13 can be applied as it is, except that the number of divisions of the backlight block is ten times that of the conventional one. Therefore, here, the description will focus on differences from the operation of the conventional liquid crystal display device 101 described in FIG.

  Prior to the description of the operation, the replacement of FIG. 13 due to the difference in configuration will be described.

  The right side of the display of the backlight blocks 15a to 15e in FIG. 13 shows the timing of the signals indicating the ON / OFF state of each of the backlight blocks 15a to 15e. The high state indicates lighting and the low state is off. In this embodiment, the description of the backlight blocks 15a to 15e is read as follows in this embodiment.

  That is, the description of the backlight block 15a is described in the backlight blocks 150a and 150b, the description of the backlight block 15b is described in the backlight blocks 150c and 150d, the description of the backlight block 15c is described in the backlight blocks 150e and 150f, The description of the backlight block 15d is replaced with the backlight blocks 150g and 150h, and the description of the backlight block 15e is replaced with the backlight blocks 150i and 150j.

  In FIG. 13 read in this way, the pixel columns corresponding to the scanning lines G1 to G2 are opposed to the backlight block 150a, and the pixel columns corresponding to the scanning lines G3 to G4 are opposed to the backlight block 150b. . The pixel columns corresponding to the scanning lines G5 to G6 are opposed to the backlight block 150c, and the pixel columns corresponding to the scanning lines G7 to G8 are opposed to the backlight block 150d. The pixel columns corresponding to the scanning lines G9 to G10 are opposed to the backlight block 150e, and the pixel columns corresponding to the scanning lines G11 to G12 are opposed to the backlight block 150f. The pixel columns corresponding to the scanning lines G13 to G14 are opposed to the backlight block 150g, and the pixel columns corresponding to the scanning lines G15 to G16 are opposed to the backlight block 150h. The pixel columns corresponding to the scanning lines G17 to G18 are opposed to the backlight block 150i, and the pixel columns corresponding to the scanning lines G19 to G20 are opposed to the backlight block 150j.

  Under the above configuration, the description of the operation of the present embodiment will be continued with reference to FIG. 1, FIG. 4, FIG. 5, and FIG.

  The backlight control unit 190 of the liquid crystal display device 1 according to the present embodiment shown in FIG. 1 operates in accordance with the backlight control signal supplied from the timing control unit 23 so as to interlock with the above-described black insertion drive. The lighting of the blocks 150a to 150j is controlled.

  As shown in FIG. 13, the liquid crystal display device 1 according to the present embodiment moves from the top to the bottom of the display screen of the liquid crystal display panel 10 in one frame period (or one field period) as time passes. The display signal is displayed, and then black for black insertion is displayed from the top to the bottom of the display screen.

  As shown in FIG. 13, the vertical synchronization signal 200, which is also a backlight control signal, is set to the high state from the timing control unit 23 at time T1, and one frame period (or one field period) is started.

  After the time T1, the backlight control unit 190 outputs the pulse signal S1 to the gate line GL1 from the PWM signal generation circuit 191 (see FIG. 4) until the time T2, and the switching transistor Tr1 (FIG. 4) is turned ON. A predetermined current flows only through the four LEDs 2 a ′, 2 k ′, 2 b ′, and 21 ′ connected in series between the switching transistor Tr <b> 1 and the power supply voltage line 192. Accordingly, only the backlight blocks 150a and 150b that mainly illuminate the pixel columns corresponding to the scanning lines G1 to G4 can be turned on, and the other backlight blocks can be turned off.

  FIG. 5 is a diagram schematically showing temporal changes in the state of turning on / off the backlight 110 according to the present embodiment as five patterns, and the time advances in the direction of the arrow in the drawing. It should be noted that the shaded backlight block indicates that the backlight block is lit.

  The five lighting pattern diagrams sequentially showing the change in the state of turning on / off of the backlight 110 from the start time of one frame period (one field period) shown in FIG. 5 as time elapses are the periods from the time T1 to the time T2, respectively. , Corresponding to a period from time T2 to T3, a period from time T3 to T4, a period from time T4 to T5, and a period from time T5 to T6.

  Next, in the period up to the time T3 after the time T2 has elapsed, the voltage corresponding to black for black insertion is sequentially written in each pixel column corresponding to the scanning lines G1 to G4, so the gate line GL1. The pulse S1 becomes low level, and the backlights 150a and 150b are turned off. On the other hand, the backlight control unit 190 outputs a pulse signal S2 from the PWM signal generation circuit 191 (see FIG. 4) to the gate line GL2, and turns on the switching transistor Tr2 (see FIG. 4). A predetermined current flows only through the four LEDs 2c ', 2m', 2d ', and 2n' connected in series between the switching transistor Tr2 and the power supply voltage line 192. Thereby, only the backlight blocks 150c and 150d that mainly illuminate each pixel column corresponding to the scanning lines G5 to G10 can be turned on, and the other backlight blocks can be turned off.

  Hereinafter, similarly, the backlight control unit 190 controls ON / OFF of the switching transistors Tr1 to Tr5 so that two adjacent backlight blocks among the ten backlight blocks 150a to 150j are turned on simultaneously and sequentially. To do.

  In addition, after the time T6 has elapsed, until the start time T1 of the next frame period (or field period), the backlight control unit 190 switches the switching transistors Tr1 to Tr1 so that all the backlight blocks 150a to 150j are turned off. Turn off Tr5.

  The backlight control unit 190 repeats the above control every frame period (or one field period). In this way, the backlight control unit 190 follows the backlight control signal supplied from the timing control unit 23 so that the two adjacent backlights among the backlight blocks 150a to 150j are interlocked with the black insertion drive. Control is performed so that the light blocks are turned on and off simultaneously and sequentially.

  In this way, the number of divisions of the backlight 110 is doubled that of the conventional backlight 11 shown in FIG. 12, and the operation of turning on and off the two adjacent backlight blocks simultaneously is linked to the above-described black insertion drive. By doing so, the flicker that can be seen on the display screen of the liquid crystal display panel can be suppressed and the contrast and moving picture response can be improved without increasing the control circuit scale of the light source of the liquid crystal display device 101. I can do it. Furthermore, high contrast and low power consumption can be realized.

  The operation of controlling the turning on and off of the backlight 110 in conjunction with the driving of the liquid crystal display panel by a source driver or the like in the conventional liquid crystal display device 101 with reference to FIGS. Since it is the same as that described, the description thereof is omitted.

  Here, as described in FIG. 3, when the configuration that increases leakage light makes the shadows generated on the display screen of the liquid crystal display panel less visible than before, and flickers visible on the display screen can be suppressed compared to the conventional case. However, the reason why the contrast and the moving image response are not lowered will be described with reference to FIGS. 3 and 6A and 6B.

  FIG. 6A compares the conventional backlight 11 divided into five shown in FIG. 12 so that the backlight block adjacent to the lit backlight block has a luminance level of 50%. It is the schematic diagram represented as an example.

  That is, in the figure, as an example, the luminance level of each backlight block is schematically shown in a state where the central backlight block 15c is turned on and all other backlight blocks are turned off.

  In FIG. 6A, in order to facilitate the comparison with FIG. 3, it is assumed that the luminance level of the central backlight block is c. In this case, as described with reference to FIG. 3, the adjacent backlight blocks 15b and 15d are extinguished, but due to leakage light from the lit backlight block 15c, the luminance level is consequently c / 2. In addition, the luminance levels of the backlight blocks 15a and 15e at both ends thereof are c / 4 as a result.

  FIG. 6B schematically shows a change in the lighting / extinguishing state of the backlight 11 of the comparative example of FIG. 6A, and the time advances in the direction of the arrow in the drawing. A hatched backlight block indicates that the backlight block is lit.

  FIG. 3 showing the luminance level of the backlight 110 of the present embodiment is compared with FIG. 6A showing the luminance level of the backlight 11 as a comparative example.

  For example, the luminance level of the backlight blocks 150c and 150h shown in FIG. 3 is c / 4, which is the same as the luminance level c / 4 of the backlight blocks 15a and 15e shown in FIG. In addition, in the case of FIG. 3, the luminance level of the backlight block at both ends is lower than that of c / 4 than the backlight block having the luminance level of c / 4. This is because the contrast between the backlight blocks 150e and 150f that are turned on (the same area as the backlight block 15c in FIG. 6A) and the backlight block that is turned off is different from that in FIG. 6A. It means that the video response will be improved.

  In the above-described embodiment, a case has been described in which the backlight blocks of the comparative example divided into five are turned on and off at the same time for each of the backlight blocks of the backlight divided into ten. For example, a configuration in which each backlight block of the nine-divided backlight is turned on and off sequentially at the same time may be repeated. In this case, the switching transistors Tr4 and Tr5 are unnecessary, and the circuit scale can be reduced. Or the structure which repeats the operation | movement which light-extinguishes four backlight blocks simultaneously 4 blocks at a time may be sufficient. In the case of 12 divisions, the number of blocks to be lit simultaneously may be 3 blocks.

As can be seen from the above description, the number of divided backlight blocks and the number of backlight blocks to be turned on and off at the same time are preferably determined by comparing FIG. 3 and FIG. 6A. In short, if the leakage light between the backlight blocks is the same, in the backlight having a large number of divisions (see FIG. 3), the lit backlight block and the unlit backlight located farthest from the lit backlight block In the backlight having a smaller number of divisions, the number of backlight blocks interposed between the blocks is smaller (see FIG. 6A), and the backlight block that is lit and the unlit backlight that is farthest from the lit backlight block. What is necessary is just to determine so that it may become more than the number of the backlight blocks interposed between light blocks. This is because it can be said that the former configuration is relatively superior in terms of contrast and moving image responsiveness because the decrease in the luminance level is larger than that in the latter configuration. In addition, if at least two backlight blocks are simultaneously turned on by one pulse signal output from the PWM signal generation circuit, the backlight block is turned on by one pulse signal output from the PWM signal generation circuit. Compared with the circuit configuration in which the light is sequentially turned on and off one by one, the number of gate line output terminals of the PWM signal generation circuit can be reduced, so that the circuit scale can be reduced.
(Embodiment 2)
In the above-described embodiment, for example, in the configuration in which each backlight block of the 10-divided backlight is turned on and off at the same time sequentially with respect to the backlight of the comparative example divided into 5 parts, The case where there is no backlight block that keeps lighting continuously has been mainly described.

  In this embodiment, separately, as an example, each backlight block of 10 divided backlights is turned on simultaneously by four blocks, and the lighting operation and the light-off operation are sequentially repeated. The configuration in which there are two backlight blocks that are continuously lit will be described mainly with reference to FIGS.

  The backlight 110 used in this configuration has the same configuration as that shown in FIG. Further, the connection relationship of the LEDs in each backlight block is also the same as that of the above embodiment, so that the description thereof is omitted. Further, the specific circuit configuration of the backlight control unit 190 is basically the same except for the pulse signal output from the PWM signal generation circuit 193. This pulse signal will be described later with reference to FIG.

  FIG. 7 is a diagram showing the luminance level of each backlight block in a situation where the four central backlight blocks 150c to 150f are turned on simultaneously and all the other backlight blocks are turned off.

  FIGS. 8A to 8E schematically show temporal changes in the lighting / extinguishing state of the backlight 110 according to the present embodiment as five lighting patterns. Time goes in the direction. It should be noted that the shaded backlight block indicates that the backlight block is lit.

  FIG. 9 is a diagram showing a specific circuit configuration of the backlight control unit 190 and the connection relationship of LEDs in each backlight block. At the same time, in FIG. 9, a pulse signal output from the PWM signal generation circuit 193 is shown. Is schematically shown.

  Under the above configuration, the lighting operation of the backlight 110 of the liquid crystal display device according to the present embodiment will be described with reference to FIGS.

  As shown in FIG. 8, the difference from the lighting operation of the above embodiment is that there are two backlight blocks that are continuously lit at the same time.

  That is, in FIG. 8 (a), the four backlight blocks 150a to 150d are lit from time T1 to T2 (see FIG. 13), and in FIG. 8 (b), 4 backlight blocks 150a to 150d are 4 from time T2 to T3. It shows that the two backlight blocks 150c to 150f are lit. As described above, in the present embodiment, for example, two common backlights among the four backlight blocks that are lit during each period from the period T1 to the period T2 and from the period T2 to the period T3. The light blocks 150c to 150d are lit continuously. Similar lighting operations are sequentially performed for subsequent times T3 to T4 and T4 to T5 as shown in FIGS. 8C and 8D, but from time T5 to T6, as shown in FIG. 8E. In addition, the backlight blocks 150i and 150j and 150a and 150b are turned on. In the next one frame period, the lighting pattern of FIG. 8A is sequentially repeated again from the lighting pattern of FIG.

  The above-described lighting pattern is repeated by sequentially outputting the pulse signals SS1 to SS5 to the gate lines GL1 to GL5 from the PWM signal generation circuit 193 shown in FIG. 9 and turning the switching transistors Tr1 to Tr5 on and off. Done.

  Specifically, as shown in FIG. 9, the PWM signal generation circuit 193 outputs a pulse signal SS1 to the gate line GL1 from time T1 to T2, and then to the gate line GL2 from time T1 to T3. The pulse signal SS2 is output. Similarly, pulse signals SS3, SS4, and SS5 are output to the gate lines GL3, GL4, and GL5 from time T2 to T4, from T3 to T5, and from T4 to T6, respectively. Here, the point in time T1 to T6 is one frame period, which is different from the timing chart of FIG.

  In this way, the number of divisions of the backlight 110 is doubled that of the conventional backlight 11 shown in FIG. 12, and the four adjacent backlight blocks are turned on at the same time. When the block is turned on, the operation of successively turning on two of the four backlight blocks that were turned on immediately before is sequentially repeated. This series of operations is linked to the above-described black insertion drive. By doing so, the flicker seen on the display screen of the liquid crystal display panel can be suppressed and the contrast and moving image response can be improved without increasing the control circuit scale of the light source of the liquid crystal display device of this embodiment. Can be planned. Furthermore, high contrast and low power consumption can be realized.

  As can be seen from the above explanation, when there are multiple backlight blocks that continue to be lit continuously in the change of the lighting and turning off of the backlight block, the number of divisions of the backlight block and the backlight that is turned on and off at the same time As described in the comparison between FIG. 3 and FIG. 6A, the number of light blocks is preferably as long as the leakage light between the backlight blocks is the same. In the backlight (refer to FIG. 3), the number of divided backlight blocks is more than the number of divided backlight blocks interposed between the lit backlight block and the lit backlight block farthest from the lit backlight block. In a small number of backlights (see FIG. 6A), the lit backlight block and the unlit backlight block located farthest from the lit backlight block. Backlight blocks may point be determined as larger than the number of Off interposed between is the same as that described in the first embodiment. Furthermore, in the case of this embodiment, the number of backlight blocks that are simultaneously turned on by one pulse signal output from the PWM signal generation circuit is three or more, and the number of backlight blocks that are turned off simultaneously is set. Compared to the conventional circuit configuration in which the backlight blocks are sequentially turned on and off one by one by one pulse signal output from the PWM signal generation circuit if the number is less than the number of backlight blocks to be turned on simultaneously and two or more. Since the number of gate line output terminals of the PWM signal generation circuit can be reduced, the circuit scale can be reduced.

  In the above embodiment, the backlight control unit 190 displays the display screen area facing the backlight blocks 150a to 150j in the display screen of the liquid crystal display panel 10, as shown in FIGS. The backlight blocks 150a to 150j are controlled to be turned on and off in conjunction with the driving of the liquid crystal display panel 10. However, the present invention is not limited to this, and for example, the backlight control unit 190 has different timings from those in FIG. You may control lighting of 150j and light extinction.

  In the above embodiment, the OCB mode liquid crystal is used for the liquid crystal layer of the liquid crystal display panel 10, but a liquid crystal other than the OCB mode liquid crystal may be used. For example, a TN (twisted nematic) type liquid crystal layer, an STN (Super-Twisted Nematic) mode liquid crystal layer, a DSM (Dynamic Scattering Mode) liquid crystal layer, an ECB (Electrically Controlled Birefringence mode). ) Liquid crystal layer, VA (Vertically Aligned) mode liquid crystal layer, or the like may be used. In order to bring the liquid crystal display panel 10 closer to an impulse-type display such as a CRT, it is more preferable to use a liquid crystal having high-speed response.

  Furthermore, as described above, the liquid crystal display device 1 according to the above embodiment has been described as a liquid crystal display device using an OCB mode liquid crystal display element in the same manner as the liquid crystal display device 101 described in the background art. That is, it is preferable to use an OCB mode liquid crystal display element in terms of high-speed response than to use a TN (Twisted Nematic) alignment liquid crystal display panel.

  However, this is not limited to the case where the liquid crystal display panel 10 of the liquid crystal display device 1 of the present embodiment uses an OCB mode liquid crystal display element as described above.

  Further, as the liquid crystal display panel 10 of the liquid crystal display device 1 of the above-described embodiment, black insertion is performed using a liquid crystal display panel using a liquid crystal layer that does not require reverse transition prevention driving, such as a TN (Twisted Nematic) alignment liquid crystal display panel. Also in the case of driving, the above embodiment can be applied as follows. That is, in the case of such a liquid crystal display device, it is not necessary to perform the transfer driving described in the above embodiment. The rest is the same as the above embodiment.

  In the above embodiment, the light source of the backlight 110 has been described as the LEDs 2a ′ to 2j ′ and the LEDs 2k ′ to 2t ′. However, the present invention is not limited to this, and a cold cathode tube may be used as the light source of the backlight 110. I do not care. Further, a display device using an EL element as a light source of the backlight 110 may be used. In short, it is only necessary to use a light source having high-speed response as the light source of the backlight 110.

  Moreover, although the said embodiment demonstrated LED as a light source of the backlight 110 each provided in the both sides of each backlight block, it is not restricted to this. Each backlight block may be provided on one side.

  Furthermore, although the backlight 110 is divided into ten backlight blocks 150a to 150j in the above embodiment, the present invention is not limited to this. The backlight 110 may be divided into at least three or more backlight blocks, and at most, the backlight 110 is divided into a number of backlight blocks equal to the number of pixels (the number of scanning lines) in the vertical direction of the liquid crystal display panel. Just do it. Note that the number of backlight blocks equal to the number of scanning lines from about 1/5 of the number of pixels in the vertical direction (the number of scanning lines) of the liquid crystal display panel may be configured using, for example, an EL display device. Is possible.

  In the above-described embodiment, each of the backlight blocks 150a to 150j has a luminance level of 50% based on the higher luminance as a result of leakage light between adjacent backlight blocks. However, the present invention is not limited to this. In short, streak-like shadows on the boundary surfaces between the backlight blocks can be made inconspicuous, and the flickering visible on the display screen of the liquid crystal display panel can be achieved without increasing the scale of the light source control circuit of the liquid crystal display device 101. Can be suppressed as compared with the prior art, and the contrast and moving image response can be improved.

  Further, each backlight block may be designed in advance so that the amount of light propagating to another adjacent backlight block is different. Even in such a case, the above embodiment can be applied.

  In the above embodiment, the case where the light source is immediately turned off during the turn-off period of each of the backlight blocks 150a to 150j has been described. However, the present invention is not limited to this. A configuration in which the luminance is gradually decreased may be used.

  In the above embodiment, the case where the light source is immediately turned on in the lighting period of each of the backlight blocks 150a to 150j has been described. However, the present invention is not limited to this. A configuration in which the luminance is gradually increased may be used. Furthermore, among the adjacent backlight blocks, the brightness of the backlight blocks that are extinguished is gradually reduced, and in parallel, the operation of gradually increasing the brightness of the backlight blocks that are lit is simultaneously performed. There may be. In this way, the backlight block that is in the lighting and extinguishing boundary, but not in the fully lit state and not in the fully extinguishing state, is adjacent, so that the occurrence of flicker at that boundary can be further reduced.

  The liquid crystal display device and the driving method of the liquid crystal display device according to the present invention provide a liquid crystal display without increasing the control circuit scale of the light source even when the backlight is divided into a larger number of backlight blocks than in the prior art. A liquid crystal display with a backlight divided into multiple backlight blocks, which has the effect of suppressing the flickering visible on the display screen of the panel compared to the prior art and improving the contrast and video response. Useful for devices and the like.

1 is a block diagram showing a configuration of a liquid crystal display device in Embodiment 1 of the present invention. (A): Plan view of the backlight 110 of the liquid crystal display device according to the present embodiment (b): A-A ′ sectional view of the backlight 110. The figure for demonstrating the luminance level of each backlight block in the condition where the two backlight blocks of the center of the backlight used with the liquid crystal display device in this Embodiment are lighting. The figure which showed the specific circuit structure of the backlight control part 190 in this Embodiment, the connection relationship of LED in each backlight block, etc. The figure which represented typically the temporal change of the lighting-on / off state of the backlight 110 of this Embodiment as five lighting patterns. (A): As a comparative example of the backlight 110 of the present embodiment, in the conventional backlight 11 divided into five as shown in FIG. 12, the luminance level of the backlight block adjacent to the lit backlight block is shown. Schematic diagram (b): a diagram schematically showing changes in the lighting / extinguishing state of the backlight 11 of the comparative example of FIG. The figure for demonstrating the luminance level of each backlight block in the condition where the four backlight blocks above the backlight used with the liquid crystal display device in Embodiment 2 of this invention are lighting. The figure which represented typically the temporal change of the lighting-on / off state of the backlight 110 of this Embodiment as five lighting patterns. A specific circuit configuration of the backlight control unit 190 in the present embodiment, LED connection relations in each backlight block, and the like are shown. (A): A cross-sectional view schematically showing the alignment state of liquid crystal molecules included in a conventional OCB mode liquid crystal display element and showing a voltage application state (b): alignment of liquid crystal molecules included in a conventional OCB mode liquid crystal display element (C): Cross-sectional view schematically showing the alignment state of liquid crystal molecules of a conventional OCB mode liquid crystal display element and showing no voltage applied state Block diagram showing the configuration of a conventional liquid crystal display device (A): A schematic plan view of a backlight 11 of a conventional liquid crystal display device (b): A-A ′ sectional view of the backlight 11 The figure which shows an example of the timing chart of the lighting and extinction of the gate pulse and the backlight blocks 15a-15e at the time of the black insertion drive of the conventional liquid crystal display device. (A): The figure which shows the shadow part displayed on the display panel of the conventional liquid crystal display device (b): The figure which shows the shadow part displayed on the display panel of the conventional liquid crystal display device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,101 Liquid crystal display device 2 Source driver 3 Gate driver 4 Controller 10 Liquid crystal display panel 11, 110 Backlight 12a, 12b, 12c, 12d, 12e Light guide plate 2a, 2b, 2c, 2d-2t LED
2a ′, 2b ′, 2c ′, 2d ′ to 2t ′ LEDs
15a, 15b, 15c, 15d, 15e Backlight blocks 150a, 150b, 150c to 150j Backlight blocks 16a, 16b, 17c Shadow portion 17 Liquid crystal drive voltage generation circuit 19, 190 Backlight control portion 21 Signal processing portion 22 Frame memory 23 Timing control unit 24 D / A conversion unit 25 Shift register 191, 193 PWM signal generation circuit 192 Power supply voltage line 200 Vertical synchronization signal

Claims (7)

A liquid crystal display panel;
A backlight having a plurality of backlight blocks in which a light source is disposed and illuminates the liquid crystal display panel with light emitted from the light source;
A backlight control unit that performs control to sequentially turn on and off the light at least two backlight blocks adjacent to each other among the plurality of backlight blocks;
A liquid crystal display device.   The plurality of backlight blocks have a boundary between the backlight blocks such that the lower brightness results in a lower predetermined luminance level due to leakage light between adjacent backlight blocks. The liquid crystal display device according to claim 1, wherein the surface is adjusted.   3. The liquid crystal display device according to claim 2, wherein in the control, the number of the backlight blocks that are turned on simultaneously is the same as the number of backlight blocks that are turned off simultaneously among the backlight blocks that are turned on simultaneously.   3. The liquid crystal display device according to claim 2, wherein in the control, the number of backlight blocks that are turned on simultaneously is larger than the number of backlight blocks that are turned off simultaneously among the backlight blocks that are turned on simultaneously. Of the display period and the black insertion period provided within one field or one frame period, (1) In the black insertion period, a voltage corresponding to black data is supplied to the signal line of the liquid crystal display panel. (2) The display period includes a source driver for performing black insertion driving for supplying a voltage corresponding to display data to the signal line of the liquid crystal display panel,
The said backlight control part turns off that backlight block, when the state of the part of the display area of the said liquid crystal display panel which opposes the said backlight block is the said black insertion period. Liquid crystal display device.   The liquid crystal display device according to claim 5, wherein OCB liquid crystal is used for the liquid crystal display panel. A liquid crystal display panel, a light source disposed therein, a backlight having a plurality of backlight blocks that illuminate the liquid crystal display panel with light emitted from the light source, and a backlight that controls turning on and off of the backlight block A method of driving a liquid crystal display device comprising a control unit,
A method for driving a liquid crystal display device, wherein the control unit performs control to turn on at least two adjacent backlight blocks among a plurality of the backlight blocks at the same time and sequentially repeat the turning on and off operations.

Images