JP2008275892A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a display screen of a liquid crystal display panel looks blinking like flicker for a user when a backlight consists of a plurality of divided backlight blocks. <P>SOLUTION: A liquid crystal display device includes: the liquid crystal display panel; a backlight 110 having backlight blocks 112a to 112e which have light sources disposed therein and illuminate the liquid crystal display panel by light emitted from the light sources; a light diffusing plate 111 which diffuses light emitted from the backlight blocks to the liquid crystal display panel, toward adjacent backlight blocks beyond interfaces between respective backlight blocks; and a backlight control part 19 which controls lighting and extinction of each of the plurality of backlight blocks. The light diffusing plate 111 has V grooves 111a to 111e for limiting diffusion of the light. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device having a backlight divided into a plurality of backlight blocks.

  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. 6 is a cross-sectional view schematically showing an alignment state of liquid crystal molecules included in the OCB mode liquid crystal display element. 6 (a) and 6 (b) are cross-sectional views showing a voltage application state, and FIG. 6 (c) 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. 6 (a), FIG.6 (b), and FIG.6 (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 power of 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. 6B. 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. 6 (a) indicates a bend state when white is displayed, and a bend state 64b shown in FIG. 6 (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. 7 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 views shown in FIGS. 8A and 8B.

  FIG. 8A 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. 8B is a side view of the backlight 11.

  As shown in FIGS. 8A and 8B, the backlight 11 is divided into a plurality of backlight blocks 15a to 15e. And LED13a-13e and LED14a-14e which are light sources are each arrange | positioned at the both ends of these several backlight blocks 15a-15e.

  In addition, light guide plates 12a to 12e are further arranged in the backlight blocks 15a to 15e, respectively. Further, the boundary surfaces 12ab, 12bc, 12cd, and 12de of the adjacent light guide plates are mirror-finished so that light leakage to the adjacent light guide plate side is reduced as much as possible.

  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 LED13a-13e and 14a-14e which are the light sources of the backlight 11 inject | emit is 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. 6C, so that the bend state 64a in FIG. It is also necessary to transition 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. 9 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. 9, 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. 9 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. 9 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. 9, the timing of the signals indicating the luminance of the backlight blocks 15a to 15e is shown, and the high state represents lighting and the low state represents unlit. Show.

  As shown in FIG. 9, 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 GG20 The row faces the backlight block 15e.

  In FIG. 9, 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. 9, 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. 9, 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. 9, 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. 2, and the light guide plate is also divided like the light guide plates 12a to 12e. For this reason, streaky shadows may be seen in portions corresponding to the boundary surfaces 12ab, 12bc, 12cd, and 12de of the light guide plates 12a to 12e of the display screen of the liquid crystal display panel 10.

  The reason for the occurrence of the streaky shadow will be described in more detail. In order to suppress color shift of the display screen of the liquid crystal display panel 10 due to variations in the LEDs 13a to 13e and 14a to 14e, which are light sources, the backlight blocks 15a to 15e are light sources to the other adjacent backlight blocks 15a to 15e. The LEDs 13a to 13e and 14a to 14e are configured to leak to some extent.

  For example, when the backlight block 15a is turned on and all the backlight blocks 15b to 15e are turned off, assuming that the luminance of the portion corresponding to the backlight block 15a of the display screen of the liquid crystal display panel 10 is 100%, the liquid crystal The backlight block 15b of the display screen of the display panel 10 also leaks about 30% to 50%. When the light guide plates 12a to 12e are configured to simply contact at the boundary, the light emitted from the LEDs 13a and 14a of the backlight block 15a propagates through the light guide plate 12a and is guided to the light guide plate 12a. Diffuse reflection occurs at the boundary with the optical plate 12b. As a result, when the backlight block 15a is turned on and the backlight block 15b is turned off, the streaky shadow portion described above is formed on the light guide plate 12b side along the boundary between the light guide plate 12a and the light guide plate 12b. Occurs.

  The above-described streak-like shadow portion is generated even when beads are dispersed on the boundaries of the light guide plates 12a to 12e and an air layer is provided or when a partition is formed on the boundaries of the light guide plates 12a to 12e. .

  As shown in FIG. 9, when the backlight blocks 15a to 15e are sequentially switched on and off, the streaky shadow moves on the display screen of the liquid crystal display panel 10 and flickers like flicker to the user. It will be recognized.

  FIG. 10A and FIG. 10B show such a shadow portion. FIG. 10A shows a lighting / extinguishing pattern from the time T1 in FIG. 9 until the time T2 is reached. FIG. 10B shows a lighting / light-off pattern from the time T2 in FIG. 9 until the time T3 is reached.

  10A, 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.

  10B, the backlight block 15a extends 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. 9, the shadow portion 16b occurs on the backlight block 15b side as shown in FIG. 10A, and when the time T2 has passed, the shadow portion 16b instantly. However, as shown in FIG.10 (b), it moves to the backlight block 15a side, and becomes the shadow part 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.

  In this way, when an image is displayed on the display screen of the liquid crystal display panel 10, the backlight blocks 15a to 15e are turned 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, the contrast and the response of the moving image are reduced. Using the black insertion drive improves the moving image visibility and increases the contrast. There is a problem that the original purpose of displaying is not achieved.

  In consideration of the above-described problems of the conventional liquid crystal display device, the present invention suppresses the flicker that appears on the display screen of the liquid crystal display panel when the backlight is divided into a plurality of backlight blocks. An object of the present invention is to provide a liquid crystal display device that can be used.

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;
The backlight, the liquid crystal display panel, and the light emitted from the backlight block to the liquid crystal display panel side are diffused to the adjacent backlight block side beyond the boundary surface between the backlight blocks. A light diffusing layer provided between,
A backlight control unit that controls turning on and off for each of the plurality of backlight blocks;
The light diffusion layer is a liquid crystal display device having at least one light diffusion limiting unit for limiting the diffusion of the light at each position corresponding to each backlight block.

  In the second aspect of the present invention, the light diffusion limiting portion is a V-groove provided in parallel with the boundary surface at a position corresponding to a central portion of each backlight block. It is a liquid crystal display device.

  Further, the third aspect of the present invention includes a sheet member that linearly moves light emitted from each backlight block to the light diffusion layer side between the backlight and the light diffusion layer. Or it is the liquid crystal display device of 2nd this invention.

According to a fourth aspect of the present invention, among the display period and the black insertion period provided within one field or one frame period, (1) the 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 turns 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 present invention.

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

  The present invention exhibits an effect that, when the backlight is divided into a plurality of backlight blocks, flickering visible on the display screen of the liquid crystal display panel can be suppressed as compared with the related art.

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

  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 that of FIG. 7 except for the backlight 110, the same reference numerals are given to the same configurations, and the description thereof is omitted.

  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.

  FIG. 2A is a plan view of the backlight 110, and FIG. 2B is a side view.

  FIG. 3 is a perspective view showing a schematic configuration of the backlight 110.

  2 and 3, the same components as those in FIG. 8 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. 8 are as follows.

  As shown in FIGS. 2 and 3, the backlight 110 according to the present embodiment has a light diffusing plate 111 disposed on the upper surfaces of the plurality of backlight blocks 112 a to 112 e, that is, on the liquid crystal display panel 10 (not shown) side. It is. An example of the light diffusion layer of the present invention corresponds to the light diffusion plate 111 of the present embodiment.

  In the light diffusion plate 111, V grooves 111a to 111e are formed at respective positions corresponding to the backlight blocks 112a, 112b, 112c, 112d, and 112e. As shown in the figure, the V grooves 111a to 111e are located at positions corresponding to the centers of the backlight blocks 112a to 112e, and are arranged in parallel with the boundary surfaces 112ab to 112de of the backlight blocks. ing. An example of the light diffusion limiting unit of the present invention corresponds to the V groove of the present embodiment. In FIG. 2A, the position of the V groove formed in the light diffusion plate is represented by a broken line, and the position of the boundary surface of the backlight block 110 is represented by a two-dot chain line.

  The lower layer formed by the plurality of backlight blocks 112a to 112e reduces the amount of light leakage to the adjacent backlight block as much as possible by mirror-treating the boundary surfaces 112ab to 112de (the lit backlight block When the luminance is 100%, it is configured to be about 10% or less).

  On the other hand, the upper light diffusing plate 111 has a V-groove as a boundary surface, and the amount of light leaking to an adjacent region with the V-groove as a boundary can be controlled by adjusting the depth of the V-groove. It has become.

  In addition, the backlight 110 of this Embodiment is demonstrated as an example of the structure containing both the backlight of this invention, and the light-diffusion layer of this invention.

  Next, the operation of the backlight 110 of the liquid crystal display device according to the present embodiment will be described with reference to the drawings.

  The operation of controlling the turning on / 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 will be omitted, and here, a detailed description will be given focusing on light diffusion in the backlight 110.

  FIG. 4 is an explanatory diagram showing the operation state of turning on / off the backlight 110 in time series. That is, in the same figure, the operation states 110a, 110b, 110c, 110d, and 110e are respectively the time T1 to T2, the time T2 to T3, the time T3 to T4, the time T4 to T5, and the time T5 to T6 described in FIG. This represents the operating state during the period.

  As shown in the figure, for example, in the state 110a corresponding to the period of time T1 to T2, only the backlight block 112a is lit, and light leakage does not occur on the adjacent backlight block 112b side. The boundary surface is mirror-finished. The light emitted from the backlight block 112a toward the liquid crystal display panel 10 is incident on the regions 201 and 202 of the upper light diffusion plate 111 and diffuses, so that the shadow of the V groove 111a hardly occurs. Even if it occurs, it is not noticeable from the point A. On the other hand, since the light diffused in the region 202 reaches the V groove 111b while being attenuated, the streaky shadow of the boundary surface 112ab viewed from the point B is blurred and is not noticeable. Further, further diffusion of light to the adjacent region 203 is limited by the V-groove 111b, and the amount of light leakage from the V-groove 111b to the region 203 is also controlled by the depth of the V-groove. Therefore, the streak-like shadow of the V groove 111b seen from the point C can be made almost inconspicuous.

  Next, in the state 110b corresponding to the period of time T2 to T3, only the backlight block 112b is lit, and light leakage hardly occurs on the adjacent backlight blocks 112a and 112c side as described above. is there. Since the light emitted from the backlight block 112b toward the liquid crystal display panel 10 is incident on the regions 202 and 203 of the upper light diffusion plate 111 and diffuses, the shadow of the V-groove 111b hardly occurs. Even if it occurs, it does not stand out from the point C. On the other hand, since the light diffused in the region 202 and the region 203 reaches the V grooves 111a and 111c while being attenuated, the streak-like shadows on the boundary surfaces 112ab and 112bc viewed from the points B and D are diffused. Blurred by light and inconspicuous. Further, further light diffusion to the adjacent regions 201 and 204 is limited by the V grooves 111a and 111c, and the amount of light leakage from the V grooves 111a and 111c to the regions 201 and 204 is the same as described above. It is controlled by the depth of the V groove. Therefore, the streaky shadows of the V grooves 111a and 111c viewed from the points A and E are hardly noticeable.

  In addition, at time T2, it is a time when the backlight block 112a is turned on and the backlight block 112b is turned on, and the shadow caused by the V-groove 111b slightly generated on the region 203 side during the time T1 to T2. Disappears at time T2 to T3. Therefore, as described with reference to FIG. 10, the phenomenon that the shadow instantaneously moves from one side to the other with respect to the boundary surface does not occur, and therefore flicker does not occur. For the same reason, no flicker occurs in any of the V grooves.

  In the periods T3 to T4, T4 to T5, and T5 to T6, streak-like shadows are hardly noticeable as described above.

  Therefore, according to the configuration of the backlight 110 of the present embodiment, when black insertion driving is performed, streak-like shadows on the boundary surface between the backlight blocks can be made inconspicuous, thereby improving contrast and moving images. It is possible to suppress the occurrence of flicker while improving the visibility.

  Further, by arranging the light diffusion plate 111 on the upper surface side of the divided backlight blocks 112a to 112e, it is possible to eliminate the step between the backlight blocks.

  In the above embodiment, the configuration in which the light diffusing plate 111 is arranged on the surface of the backlight blocks 112a to 112e has been described. However, the configuration is not limited to this, and for example, between the backlight blocks 112a to 112e and the light diffusing plate 111. In addition, it is more preferable to arrange a prism sheet as the third layer. In this case, since the prism sheet has the effect of promoting the straight movement of light in the thickness direction of the sheet, it is possible to further improve the contrast.

  In the above-described embodiment, the light diffusing plate 111 is described as a single sheet-like member. However, the present invention is not limited to this.

  Moreover, in the said embodiment, regarding the backlight 110, it was set as the structure which provides V groove | channel one by one corresponding to the center position of each backlight block, but it is not restricted to this, For example, as another backlight 210, As shown in FIG. 5, two V-grooves may be provided for each backlight block. In this configuration, since the number of V grooves 111a1, 111a2,..., 111e1, 111e2 is increased, the light diffusing range in the light diffusing plate 211 can be made narrower than that of the light diffusing plate 111 in FIG. The contrast can be further improved.

  In the above-described embodiment, the backlight control unit 19 in the display screen region of the display screen of the liquid crystal display panel 10 facing the backlight blocks 112a to 112e, as shown in FIG. The backlight block 112a is controlled to be turned on and off in conjunction with the driving. However, the present invention is not limited to this. For example, the backlight control unit 19 turns on and off the backlight blocks 112a to 112e at timings different from those in FIG. You may control.

  Furthermore, in the said embodiment, the red, green, and blue color filter is provided in the opposing board | substrate of the liquid crystal display panel 10, and light which LED13a-13e and 14a-14e which are the light sources of the backlights 110 and 210 inject | emit. However, the present invention is not limited to this. For example, the liquid crystal display device 1 in the above embodiment can be operated as a so-called field sequential color liquid crystal display device.

  Here, in the field sequential color system, a color filter is not formed on the counter substrate of the liquid crystal display panel 10, and an image of three colors (red, green, and blue) is displayed in one pixel for one frame period (or one field period). In comparison with a method in which a color filter is provided on the counter substrate of the liquid crystal display panel 10, there is an advantage that higher transmittance and higher resolution can be achieved.

  That is, a red display period, a green display period, and a blue display period which are three primary colors are provided in one frame period (or one field period). A black insertion period is provided immediately after the red display period, a black insertion period is provided immediately after the green display period, and a black insertion period is also provided immediately after the blue display period.

  That is, when the liquid crystal display device 1 is of the field sequential color system, the operation of the above-described embodiment is performed in the red display period and the black display period immediately thereafter, the green display period and the black display period immediately thereafter, and blue. The display period may be repeated in the black display period immediately after that. The LEDs 13a to 13e and 14a to 14e of the backlight blocks 112a to 112e only need to be capable of emitting red, green, and blue light.

  Further, in the above-described 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.

  Further, in the above embodiment, the light sources of the backlights 110 and 210 have been described as the LEDs 13a to 13e and 14a to 14e. 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. . 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.

  Furthermore, in the above embodiment, the description has been given assuming that LEDs are provided on both sides of each backlight block as the light source of the backlight 110, but the present invention is not limited to this. Each backlight block may be provided on one side.

  Furthermore, although the backlight 110 is divided into five backlight blocks 112a to 112e in the above embodiment, the present invention is not limited to this. The backlight 110 may be divided into at least two 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 backlights equal to the number of scanning lines from about 1/5 of the number of pixels in the vertical direction of the liquid crystal display panel (the number of scanning lines) can be configured using, for example, an EL display device. It is.

  Furthermore, in the above-described embodiment, when each backlight block 112a to 112e is lit, the luminance of the backlight block adjacent to the lit backlight block is lit. Although it has been described that the light is propagated in advance so as to be 10% or less of the backlight block, the present invention is not limited to this. In short, it is only necessary that the streak-like shadows on the boundary surface between the backlight blocks are not noticeable.

  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 lighting periods of the backlight blocks 15a to 15e do not overlap each other has been described as shown in FIG. 9, but the present invention is not limited to this. For example, the backlight blocks are adjacent to each other. A configuration in which a part of the lighting period overlaps between the backlight blocks may be employed.

  In the liquid crystal display device according to the present invention, when the backlight is divided into a plurality of backlight blocks, flicker such as flicker seen on the display screen of the liquid crystal display panel can be suppressed compared to the conventional case. And is useful for a liquid crystal display device including a backlight divided into a plurality of backlight blocks.

The block diagram which shows the structure of the liquid crystal display device in the 1st Embodiment of this invention (A) Top view of the backlight 110 of the liquid crystal display device in this Embodiment (b) Side view of the backlight 110 The perspective view showing the schematic structure of the backlight 110 used with the liquid crystal display device in this Embodiment. Explanatory drawing which represented the operation state of the lighting of the backlight 110 in this Embodiment in time series Explanatory drawing which represented the operation state of lighting / extinguishing of another backlight 210 in this Embodiment in time series (A) A cross-sectional view schematically showing an alignment state of liquid crystal molecules included in a conventional OCB mode liquid crystal display element and showing a voltage application state. (B) An alignment state 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 in 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), (b): Configuration diagram of a backlight of a conventional liquid crystal display device 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, 210 Backlight 12a, 12b, 12c, 12d, 12e Light guide plate 13a, 13b, 13c, 13d, 13e LED
14a, 14b, 14c, 14d, 14e LED
15a, 15b, 15c, 15d, 15e Backlight block 112a-112e Backlight block 16a, 16b Shadow part 17 Liquid crystal drive voltage generation circuit 19 Backlight control part 21 Signal processing part 22 Frame memory 23 Timing control part 24 D / A conversion Section 25 Shift register 111, 211 Light diffusion plate

Claims (5)

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;
The backlight, the liquid crystal display panel, and the light emitted from the backlight block to the liquid crystal display panel side are diffused to the adjacent backlight block side beyond the boundary surface between the backlight blocks. A light diffusing layer provided between,
A backlight control unit that controls turning on and off for each of the plurality of backlight blocks;
The liquid crystal display device, wherein the light diffusion layer has at least one light diffusion restriction unit for restricting diffusion of the light at each position corresponding to each backlight block.   The liquid crystal display device according to claim 1, wherein the light diffusion limiting portion is a V-groove provided in parallel with the boundary surface at a position corresponding to a central portion of each backlight block.   3. The liquid crystal display device according to claim 1, further comprising: a sheet member between the backlight and the light diffusing layer that causes light emitted from the backlight blocks to travel straight to the light diffusing layer side. 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 the 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 3, wherein OCB liquid crystal is used for the liquid crystal display panel.

Images