JP2008304644A - Liquid crystal display device, driving method of liquid crystal display device, program, and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that the contrast is degraded and moving picture responsiveness is deteriorated in a conventional liquid crystal display device. <P>SOLUTION: The liquid crystal display device includes: a liquid crystal display panel 10 including signal lines and scan lines formed in a matrix, and a liquid crystal display element formed at each cross point of the signal line and the scan line; a source driver 2 for applying a voltage corresponding to a data for display, on the signal line of the liquid crystal display panel 10; a backlight 11 for illuminating the liquid crystal display panel, in which brightness can be continuously or stepwise increased; and a backlight control section 19 for controlling the brightness of the backlight 11, based on a writing voltage, that is, the voltage which the applied voltage is written on the liquid crystal display element via the signal line. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device having a backlight for illuminating a liquid crystal display panel, a driving method of the liquid crystal display device, a program, and a recording medium.

  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 a display element in an OCB (Optically Compensated Birefringence) mode 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. 19 is a cross-sectional view schematically illustrating an alignment state of liquid crystal molecules included in the OCB mode display element. 19 (a) and 19 (b) are cross-sectional views showing a voltage application state, and FIG. 19 (c) is a cross-sectional view showing a voltage non-application state.

  Nematic liquid crystal is injected between the glass substrates 61 of the liquid crystal display panel constituting the liquid crystal display device using the OCB mode display element as shown as liquid crystal molecules 62 in FIG. 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 display element is turned on, it is necessary to perform driving called transfer driving. In other words, 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. ), Driving to shift to the bend states 64a and 64b shown in FIG. The display using the bend states 64a and 64b is a characteristic of the liquid crystal display device using the OCB mode display element. The liquid crystal display device using the OCB mode display element bends depending on the voltage level. The transmittance of the panel is changed by changing the state.

  A bend state 64a shown in FIG. 19A indicates a bend state when white display is performed, and a bend state 64b of FIG. 19B indicates a bend state when black display is performed. .

  Further, in a liquid crystal display device using an OCB mode 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 transitions 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, driving called reverse transition prevention driving is performed in a liquid crystal display device using an OCB mode display element.

  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 a voltage corresponding to a 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 a pixel and an operation of applying a voltage corresponding to a 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 liquid crystal display device using a conventional OCB mode display element, in a period for displaying one frame (or one field) video, a display period in which a voltage corresponding to a video signal is applied to the pixels, 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 drive described above and extending the black insertion period, the display of the liquid crystal display device using the OCB mode display element can be brought close to an impulse-type display such as a CRT. Video visibility can be improved. This is because high-speed response, which is an advantage of the OCB mode display element, can be used. Further, by using the black insertion drive, not only the moving image visibility is improved, but also high contrast display can be performed.

  In addition, in the 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.

  Recently, a field sequential color liquid crystal display device has been developed (see, for example, Patent Document 2).

  The field sequential color liquid crystal display device is a liquid crystal display device that sequentially displays images of three primary colors (R, G, B) with one pixel without providing a color filter for each pixel. Compared to the apparatus, it has advantages such as high transmittance and high resolution.

  Therefore, if an OCB mode display element is used, black insertion drive is performed, and a field sequential color system is adopted, an impulse-type display such as a CRT can be realized, and a high transmittance, high resolution, and high contrast liquid crystal can be realized. A display device can be realized.

  FIG. 20 is a block diagram showing a main part of a conventional liquid crystal display device 101 that performs black insertion driving in the conventional field sequential color system and drives a backlight in conjunction with driving of a liquid crystal display panel by a source driver or the like. It is.

  The liquid crystal display device 101 includes a source driver 2, a gate driver 3, a liquid crystal display panel 10, a backlight 111, and a backlight control unit 119.

  The liquid crystal display panel 10 is an active matrix liquid crystal display panel. That is, in the liquid crystal display panel 10, the signal lines and the scanning lines are arranged in a matrix on the array substrate, and a pixel is formed at each intersection thereof.

  Each pixel has a switching element, a storage capacitor, and a display layer. Further, the display element includes a pixel electrode, a counter electrode, a liquid crystal layer sandwiched between the pixel electrode and the counter electrode, and the like. An OCB mode liquid crystal is used as the liquid crystal layer. Further, since the liquid crystal display device 101 is a field sequential method, red, green, and blue color filters are not formed on the counter substrate of the liquid crystal display panel 10.

  The backlight 111 is disposed on the back surface of the liquid crystal display panel 10, and emits light of R (Red), G (Green), and B (Blue) colors that are light sources, and light emitted from the LEDs. A light guide plate or the like for guiding the light to the liquid crystal display panel 10 is provided.

  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 supplies a voltage corresponding to each color of the display signal during the display period of each color (R, G, B) in the display period, and supplies a voltage corresponding to black during the black insertion period to the liquid crystal display panel. 10 is a circuit for supplying 10 signal lines.

  Next, the operation of the conventional liquid crystal display device 101 will be described.

  When the power supply 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. 19C, so that the bend state 64a in FIG. Alternatively, the transition to the bend state 64b in 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. By the transition driving, 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 becomes possible.

  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.

  The gate driver 3 of the liquid crystal display device 101 sequentially applies gate pulses to the scanning lines formed on the liquid crystal display panel 10. Then, in synchronization with the timing when the gate driver 3 applies the gate pulse to the scanning line, the source driver 2 applies a voltage corresponding to each color of the display data to the signal line of the liquid crystal display panel 10, and During the insertion period, a voltage corresponding to black is applied. The voltage applied to the signal line is written to the display element of each pixel of the liquid crystal display panel 10.

  The backlight control unit 119 controls lighting and extinguishing of the backlight 111 so as to interlock with driving of the liquid crystal display panel 10 by the source driver 2 and the like.

  As a result, the black color due to the video or black insertion is displayed on the display screen of the liquid crystal display panel 10.

  FIG. 21 is a timing chart showing the voltage waveform written to the display element of a specific pixel of the conventional liquid crystal display device 101 and the lighting / extinguishing state of each color of the backlight 111.

  In FIG. 21, the time has passed from the left side to the right side as viewed in the drawing.

  In FIG. 21, reference numeral 75a denotes a voltage waveform written to the display element of any one pixel (hereinafter referred to as the first pixel) existing on the scanning line that is scanned first in one frame (or one field) period. , 75c are voltage waveforms written in the display element of any one pixel (hereinafter referred to as the last pixel) existing on the scanning line scanned last in one frame (or one field) period, and 75b is A specific pixel (on a scanning line located in the middle of a scanning line that is scanned first in one frame (or one field) and a scanning line that is scanned last in one frame (or one field) ( This is a voltage waveform written in the display element (hereinafter referred to as the middle pixel).

  Note that FIG. 21 illustrates a case where voltages corresponding to the same color are written in the first pixel, the middle pixel, and the last pixel in order to facilitate understanding.

  Therefore, the voltage waveform 75b written to the display element of the middle pixel is a waveform obtained by simply shifting the voltage waveform 75a written to the display element of the first pixel to the right side. The voltage waveform 75c written to the display element of the last pixel is a waveform obtained by simply shifting the voltage waveform 75b written to the display element of the middle pixel to the right.

  In FIG. 21, 74 indicates a black voltage for black insertion driving, 71 indicates a voltage corresponding to the red color of the display data, indicates a red writing voltage to be written to the pixel in the red display period, and 72 indicates , Indicates a voltage corresponding to the green color of the display data, indicates a green write voltage to be written to the pixel in the green display period, 73 indicates a voltage corresponding to the blue color of the display data, and blue write to be written to the pixel in the blue display period The voltage is shown.

  In FIG. 21, R_LED, G_LED, and B_LED respectively indicate the luminance of the backlight 111 when the red LED of the backlight 111 is lit, the luminance of the backlight 111 and the luminance of the backlight 111 when the green LED of the backlight 111 is lit. The luminance of the backlight 111 when the blue LED of the light 111 is turned on is shown. As is clear from R_LED, G_LED, and B_LED, when the backlight 111 is lit in each color, the backlight 111 is lit with a constant luminance.

  The conventional liquid crystal display device 101 drives the backlight 111 as follows in conjunction with the driving of the liquid crystal display panel by a source driver or the like.

  As is clear from FIG. 21, in the conventional liquid crystal display device 101, when one frame period (or one field period) starts and the red display period shown as red writing in FIG. When the voltage corresponding to the red color of the display data is started to be written, the red LED as the light source of the backlight 111 is turned on. The backlight 111 continues to be lit at a constant brightness while being lit.

  Further, in the conventional liquid crystal display device 101, when the green display period shown as green writing in FIG. 21 is started, the voltage corresponding to the green color of the display data is started to be written to the pixels on the scanning line that is scanned first. The green LED that is the light source of the backlight 111 is turned on. The backlight 111 continues to be lit at a constant brightness while being lit.

  In the conventional liquid crystal display device 101, when the blue display period shown as blue writing in FIG. 21 is started, the voltage corresponding to the blue color of the display data is started to be written to the pixels on the scanning line that is scanned first. The blue LED that is the light source of the backlight 111 is turned on. The backlight 111 continues to be lit at a constant brightness while being lit.

  Thus, the conventional liquid crystal display device 101 lights the backlight 111 simultaneously with the start of the display period of each color in the display period of each color. That is, the conventional liquid crystal display device 101 performs control to turn on the backlight 111 in the first half and turn off the backlight in the second half in the display period of each color. In other words, the liquid crystal display device 101 controls the backlight 111 to be turned off during most of the black insertion period shown as black writing in FIG. The backlight 111 continues to be lit at a constant brightness while being lit.

Therefore, by using the liquid crystal display device 101, display with high contrast is possible and power consumption can be reduced.
JP 2003-280617 A JP 2005-191006 A

  However, the conventional liquid crystal display device 101 performs an operation combining black insertion driving and field sequential driving.

  Therefore, an ordinary liquid crystal display device that does not perform black insertion driving or field sequential driving displays an image of one frame (or one field) on a liquid crystal display panel in one frame period (or one field period). In the conventional liquid crystal display device 101, in one frame period (or one field period), a red component of a video, a black component, a green component of a video component, a black component, a blue component of a video component, and a black component are displayed on the liquid crystal display panel 10. It is necessary to display them on the liquid crystal display panel in order. Therefore, the liquid crystal display device 101 must be driven at a higher speed than a normal liquid crystal display device.

  For this reason, as shown in FIG. 21, the backlight block 111 is turned on before the voltage written in the display element of the pixel has risen sufficiently until it reaches the voltage applied to the source signal line.

  In addition, in the case where the lighting period of the backlight 111 is made longer than that in FIG. 21, the voltage corresponding to black is applied to the liquid crystal display element of the pixel during the black insertion period, and is applied to the liquid crystal display element of the pixel. It is possible that the backlight 111 is lit even when the voltage deviates from the voltage corresponding to the display color.

  The backlight 111 always keeps lighting at a constant luminance during the lighting period. Accordingly, as shown in FIG. 21, the backlight 111 has a period during which the voltage written in the pixel display element rises or falls during the lighting period, and a voltage written in the pixel display element. Is lit at the same brightness as the period when the is standing up.

  For this reason, in the conventional liquid crystal display device, there exists a subject that contrast falls and moving image response falls.

  For this reason, the conventional liquid crystal display device has a problem that power consumption cannot be reduced.

  Such a problem typically occurs when an operation combining black insertion driving and field sequential driving is performed as in the conventional liquid crystal display device 101, but is not limited thereto.

  In other words, the conventional liquid crystal display device that does not perform field sequential driving and the conventional liquid crystal display device that does not perform field sequential driving or black insertion driving have also occurred. For example, it may occur when the number of pixels of the liquid crystal display panel of the liquid crystal display device is large or when the temperature of the liquid crystal display panel of the liquid crystal display device is lowered.

  In view of the above problems, an object of the present invention is to provide a liquid crystal display device, a driving method of the liquid crystal display device, a program, and a recording medium that can suppress a decrease in contrast.

  Another object of the present invention is to provide a liquid crystal display device, a driving method of the liquid crystal display device, a program, and a recording medium that can suppress a decrease in moving image response in consideration of the above problems. .

  Another object of the present invention is to provide a liquid crystal display device, a driving method of the liquid crystal display device, a program, and a recording medium that can reduce power consumption in consideration of the above problems.

In order to solve the above-described problem, the first aspect of the present invention includes a signal line and a scanning line formed in a matrix, and a liquid crystal display element formed corresponding to an intersection of the signal line and the scanning line. A liquid crystal display panel;
A source driver that applies an applied voltage corresponding to display data to a signal line of the liquid crystal display panel;
The luminance can be increased or decreased continuously or stepwise, and a backlight for illuminating the liquid crystal display panel;
A backlight control unit that controls the luminance of the backlight based on a write voltage in which the applied voltage is written to the liquid crystal display element via the signal line during a predetermined lighting period of the backlight; A liquid crystal display device.

Further, according to a second aspect of the present invention, the liquid crystal display panel has a storage capacitor for each liquid crystal display element,
The write voltage is the liquid crystal display device according to the first aspect of the present invention, wherein the applied voltage held in the storage capacitor via the signal line is a voltage written to the liquid crystal display element.

The third aspect of the present invention includes a storage unit that stores in advance backlight luminance information that associates the luminance of the backlight with the writing voltage,
The backlight control unit is the liquid crystal display device according to the first aspect of the present invention, which controls the luminance of the backlight using the backlight luminance information.

The fourth aspect of the present invention includes a temperature sensor for detecting the temperature of the liquid crystal display panel,
The storage unit stores a plurality of backlight luminance information according to the detected temperature,
The backlight control unit controls the luminance of the backlight using the backlight luminance information corresponding to the detected temperature among the plurality of types of backlight luminance information, and the liquid crystal according to the third aspect of the present invention. It is a display device.

  According to a fifth aspect of the present invention, controlling the luminance of the backlight based on the writing voltage sets the luminance of the backlight to a luminance according to a ratio of the writing voltage to the applied voltage. The liquid crystal display device according to the first aspect of the present invention.

  According to a sixth aspect of the present invention, when the voltage written in the liquid crystal display element reaches the applied voltage, the write voltage is (1) a scan scanned at the beginning of one frame period or one field period. A voltage written in the liquid crystal display element existing on the line, and (2) a voltage written in the liquid crystal display element existing on the scanning line scanned at the end of the one frame period or the one field period. The liquid crystal display device of the first aspect of the present invention.

  According to a seventh aspect of the present invention, when the voltage written in the liquid crystal display element does not reach the applied voltage, the write voltage is the liquid crystal present on the scanning line located at the center of the liquid crystal display panel. The liquid crystal display device according to the first aspect of the present invention, which is the writing voltage of the display element.

  According to an eighth aspect of the present invention, in the liquid crystal display device according to the first aspect, the backlight control unit controls the luminance of the backlight by setting a duty of a PWM signal supplied to the backlight. It is.

  The ninth aspect of the present invention is the liquid crystal display device according to the first aspect of the present invention, wherein the backlight control unit controls the luminance of the backlight by controlling the voltage supplied to the backlight.

  The tenth aspect of the present invention is the liquid crystal display device according to the first aspect of the present invention, wherein the backlight control unit controls the luminance of the backlight by controlling a current supplied to the backlight.

The eleventh aspect of the present invention is a liquid crystal display panel having signal lines and scanning lines formed in a matrix, and liquid crystal display elements formed corresponding to the intersections of the signal lines and the scanning lines;
A source driver that applies an applied voltage corresponding to display data to a signal line of the liquid crystal display panel;
A method of driving a liquid crystal display device that drives a liquid crystal display device that can be increased or decreased in luminance continuously or stepwise and includes a backlight that illuminates the liquid crystal display panel,
A method for driving a liquid crystal display device, comprising: a backlight control step for controlling the luminance of the backlight based on a write voltage in which the applied voltage is a voltage written to the liquid crystal display element via the signal line. is there.

  Further, a twelfth aspect of the present invention is based on a write voltage, which is a voltage in which the applied voltage is written to the liquid crystal display element via the signal line, in the liquid crystal display device drive method of the eleventh aspect of the present invention. It is a program for causing a computer to execute a backlight control step for controlling the luminance of the backlight.

  The thirteenth aspect of the present invention is a recording medium that records the program of the twelfth aspect of the present invention, and is a recording medium that can be processed by a computer.

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

(First embodiment)
In the first embodiment, a liquid crystal display device which is an embodiment of the liquid crystal display device of the present invention will be described, and an embodiment of a driving method of the liquid crystal display device of the present invention will also be described.

  FIG. 1 shows a block diagram of a liquid crystal display device 1 according to the first embodiment.

  The liquid crystal display device 1 according to the first embodiment is a field-sequential liquid crystal display device that performs black insertion driving, similarly to the conventional liquid crystal display device 101.

  The liquid crystal display device 1 according to the first embodiment 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, an input power supply 16, a liquid crystal drive voltage generation circuit 17, a dimming control. Unit 18, backlight control unit 19, and optical sensor unit 26.

  The liquid crystal display panel 10 is an active matrix liquid crystal display panel. That is, in the liquid crystal display panel 10, the signal lines and the scanning lines are arranged in a matrix on the array substrate, and a pixel is formed at each intersection thereof. Each pixel has a switching element, a storage capacitor, and a display element. Further, the display element includes a pixel electrode, a counter electrode, a liquid crystal layer sandwiched between the pixel electrode and the counter electrode, and the like. An OCB mode liquid crystal is used as the liquid crystal layer. Further, since the liquid crystal display device 1 is a field sequential method, red, green, and blue color filters are not formed on the counter substrate of the liquid crystal display panel 10.

  The input power supply 16 supplies power to the backlight 11, the controller 4, the liquid crystal drive voltage generation circuit 17, the dimming unit 18, and the like.

  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 supplies a voltage corresponding to each color of the display signal during the display period of each color (R, G, B) in the display period, and supplies a voltage corresponding to black during the black insertion period to the liquid crystal display panel. 10 is a circuit for supplying 10 signal lines.

  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.

  Based on the luminance of each color (R, G, B) of the backlight 11 detected by the optical sensor unit 26, the light control unit 18 determines the lighting period of the LED of each color (R, G, B) of the backlight 11. The circuit adjusts the luminance and / or chromaticity of the backlight by adjusting the ratio of each color to the display period (red display period, green display period, blue display period).

  The backlight 11 is disposed on the back surface of the liquid crystal display panel 10 and emits light of each color of R (Red), G (Green), and B (Blue), which is a light source, and light emitted from the LED. A light guide plate or the like for guiding the light to the liquid crystal display panel 10 is provided.

  The backlight 11 is provided with an optical sensor unit 26 that detects the luminance of each color of R, G, and B.

  The backlight 11 is disposed on the back of the active matrix liquid crystal display panel 10 and is divided into a plurality of backlight blocks. Each backlight block has a red LED, a green light source, and a green light source. An LED, a blue LED, and a light guide plate are provided.

  An outline of the backlight 11 is shown in FIGS. FIG. 2A 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. 2B is a side view of the backlight 11.

  As shown in FIGS. 2A and 2B, the backlight 11 is divided into a plurality of backlight blocks 15a to 15e. In each of the plurality of backlight blocks 15a to 15e, LEDs 13a to 13e and LEDs 14a to 14e, which are light sources, are respectively arranged. Here, LED13a-13e and LED14a-14e are respectively comprised from red LED, green LED, and blue LED.

  Further, light guide plates 12a to 12e are respectively arranged in the plurality of backlight blocks 15a to 15e. 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.

  Each of the backlight blocks 15a to 15e is provided with optical sensor units 16a to 16e (corresponding to the optical sensor unit 26 in FIGS. 1 and 3).

  4A and 4B show an example of the optical sensor units 15a to 15e. 4A is a plan view of any one of the optical sensor units 15a to 15e, and FIG. 4B is a side view of any one of the optical sensor units 15a to 15e. FIG. As shown in FIGS. 4A and 4B, each of the photosensor portions 15a to 15e has three photodetecting elements 36a, 36b, and 36c formed on a substrate 37, and the photodetecting element 36a. , 36b, 36c, color filters 35a, 35b, 35c are formed. The color filters 35a, 35b, and 35c are color filters that transmit red, green, and blue light, which are the three primary colors, respectively. The light detection elements 36a, 36b, 36c and the color filters 35a, 35b, 35c are covered with a transparent cover 38 such as glass.

  The backlight control unit 19 transmits a backlight control signal (clock signal, horizontal synchronization signal) sent from the timing control unit 23 so that the lighting ratio of each color (R, G, B) determined by the dimming unit 18 is obtained. , Vertical synchronization signals, etc.) are used to determine the lighting start timing and lighting end timing of the LEDs 13a to 13e and LED 14a to LED 14e, and the respective LEDs 13a to 13e and LEDs 14a to 14e are turned on at the determined lighting start timing. The LEDs 13a to 13e and LEDs 14a to 14e are turned off at the determined lighting end time.

  That is, the backlight control unit 19 controls turning on / off of the LEDs 13a to 13e and 14a to 14e of the plurality of backlight blocks 15a to 15e in conjunction with the driving timing of the liquid crystal display panel 10 by the source driver 2 or the like. Is. Further, the backlight control unit 19 controls the luminance of the backlight block that is lit among the plurality of backlight blocks 15a to 15e.

  Based on the luminance of each color (R, G, B) of each of the backlight blocks 15a to 15e detected by the light sensor unit 26, the light control unit 18 uses each color (R, G, and R) of each backlight block 15a to 15e. For the LEDs 13a to 13e and 14a to 14e of B), the luminance and / or chromaticity of the backlight is dimmed by adjusting the ratio of the lighting period of the LED of that color to the display period of each color.

  Note that the ratio of the lighting periods of the LEDs 13a to 13e and 14a to 14e of the corresponding color with respect to the display period of each color is referred to as the lighting ratio of the color.

  FIG. 3 is a diagram showing details of an illumination system such as the light control unit 18, the backlight control unit 19, and the backlight 11 in the liquid crystal display device 1 of FIG. 1.

  The dimming unit 18 includes a dimming control unit 33, a reference value storage unit 40, and a lighting ratio storage unit 44.

  The reference value storage unit 40 is a semiconductor memory in which a reference luminance and / or chromaticity is recorded in advance.

  The dimming control unit 33 determines that each of the backlight blocks 15a to 15e has a reference value storage unit 40 based on the detection result of the luminance of each of the backlight blocks 15a to 15e sent from each of the light sensor units 16a to 16e. The lighting ratios of the respective colors of the LEDs 13a to 13e and 14a to 14e of the backlight blocks 15a to 15e are determined so as to match the reference luminance and / or chromaticity stored in Is a circuit to be stored.

  The lighting ratio storage unit 44 is a semiconductor memory that stores the lighting ratio of each color of the LEDs 13a to 13e and 14a to 14e for each of the backlight blocks 15a to 15e.

  The backlight control unit 19 includes an analysis result storage unit 45, a calculation unit 46, a time storage unit 47, and a luminance table storage unit 48.

  The analysis result storage unit 45 is a semiconductor memory that stores various times obtained by analyzing a voltage waveform written to a display element of a pixel.

  The calculation unit 46 determines the lighting start timing and lighting end timing of each of the backlight blocks 15a to 15e based on information on various times stored in the analysis result storage unit 45, and the determined lighting start timing and lighting determined. The end time is stored in the time storage unit 47.

  The time storage unit 47 is a semiconductor memory that stores the lighting start timing and lighting end timing of each of the backlight blocks 15a to 15e.

  The luminance table storage unit 48 is a semiconductor memory that stores a luminance table for determining the luminance of each color of the LEDs 13a to 13e and 14a to 14e of the backlight blocks 15a to 15e from the time elapsed from the start of the display period of each color. is there.

  Note that the luminance table of the present embodiment is an example of backlight luminance information of the present invention.

  Next, the operation of the liquid crystal display device 1 according to the first embodiment will be described, and an embodiment of the liquid crystal display device driving method of the present invention will also be described.

  When the power source of the liquid crystal display device 1 is turned on, the liquid crystal display device 1 performs transfer driving in the same manner as the conventional liquid crystal display device 101 described in the background art.

  When the transfer driving is completed and the liquid crystal display device 1 can perform the display operation, the liquid crystal display device 1 starts the display operation.

  In one frame period (or one field period), a red display period, a black insertion period, a green display period, a black insertion period, a blue display period, and a black insertion period are provided in this order.

  FIG. 5 shows an equivalent circuit of a pixel to which a video signal is written as a pixel 82. In FIG. 5, the pixel 82 includes a TFT 83 that is a switching element, a storage capacitor 84, and a display element 85. The display element 85 includes a pixel electrode, a portion of a counter electrode facing the pixel electrode, and a liquid crystal layer sandwiched between the pixel electrode and the counter electrode.

  The gate driver 3 sequentially applies a scanning voltage to each scanning line, and when the scanning voltage is applied, the switching element (TFT) 83 of each pixel 82 arranged in the scanning line is turned on. In accordance with the timing, the source driver 2 writes a voltage corresponding to each color of display data or a voltage corresponding to black to each pixel 82 arranged on the scanning line through each signal line.

  Thereby, the voltage corresponding to each color of the display data or the voltage corresponding to black is written and held in the storage capacitor 84 of each pixel, and the voltage corresponding to each color of the display data is stored in the liquid crystal display element 85. A voltage corresponding to black is written.

  Even after the switching element (TFT) 83 is changed from the on state to the off state, a voltage corresponding to the video signal held in the storage capacitor 84 or a voltage corresponding to black is written in the display element 85. The voltage written to the display element 86 changes relatively slowly and reaches a voltage corresponding to the video signal held in the storage capacitor 84.

  Thereby, the liquid crystal molecules 62 (FIGS. 19A and 19B) of the liquid crystal display panel 10 are modulated, and the transmittance of light emitted from the backlight 11 changes. As a result, an image corresponding to the video signal is displayed on the liquid crystal display panel 10. The details of the waveform of the voltage written in the display element 86 will be described later.

  Next, the operation of the illumination system such as the backlight 11 will be described.

  The operation of the illumination system such as the backlight 11 will be described by focusing on the backlight block 15a constituting the backlight 11. However, the backlight blocks 15b to 15e have the same operation as the backlight block 15a. Therefore, the description of the operation of the backlight blocks 15b to 15e is omitted.

  FIG. 6 shows the relationship between the backlight block 15a and the display area portion of the liquid crystal display panel 10 facing the backlight block 15a. In FIG. 6, as indicated by arrows (scanning direction), scanning voltages are sequentially applied to the scanning lines 76 from the top to the bottom of the sheet.

  Therefore, the scanning line shown as the first scanning line 77a is first scanned in the portion of the display area of the liquid crystal display panel 10 facing the backlight block 15a. In addition, the scanning line shown as the last scanning line 77c is finally scanned in the display area portion of the liquid crystal display panel 10 facing the backlight block 15a. The scanning line shown as the middle scanning line 77b is located between the first scanning line 77a and the last scanning line 77c, and the timing when the first scanning line 77a is scanned and the last scanning line 77c are Scanning is performed at a time intermediate to the scanning time.

  In FIG. 6, the first pixel 78a is an arbitrary specific pixel existing on the first scanning line 77a, and the middle pixel 78b is an arbitrary specific pixel existing on the central scanning line 77b. The last pixel 78c is an arbitrary specific pixel existing on the last scanning line 77c. The first pixel 78a, the middle pixel 78b, and the last pixel 78c have the same configuration as the pixel 82 described in FIG.

  FIG. 7 shows voltage waveforms written in the display elements of the first pixel 78a, the middle pixel 78b, and the last pixel 78c shown in FIG. 6, and the ON / OFF states of the LEDs of the respective colors in the backlight block 15a. It is a timing chart figure. In FIG. 7, time elapses from the left side toward the right side as viewed on the paper.

  Reference numeral 75a denotes a voltage waveform written to the display element of the first pixel 78a.

  Reference numeral 75b denotes a voltage waveform written to the display element of the middle pixel 78b.

  75c is a voltage waveform written in the display element of the last pixel 78c.

  In FIG. 7, R_LED, G_LED, and B_LED respectively indicate the on / off state and brightness of the red LED, the green LED, and the blue LED among the LEDs 13a and 14a that are the light sources of the backlight block 15a.

  In FIG. 7, reference numeral 74 denotes a black voltage for black insertion driving, 71 denotes a voltage corresponding to red of display data, 72 denotes a red writing voltage to be written to the pixel in the red display period, and 72 denotes , A voltage corresponding to the green color of the display data, a green write voltage to be written to the display element of the pixel 78 during the green display period, and a voltage 74 corresponding to the blue color of the display data, and the pixel 78 during the blue display period. The blue write voltage to be written to the display element is shown.

  For ease of understanding, FIG. 7 illustrates a case where the first pixel 78a, the middle pixel 78b, and the last pixel 78c all display the same color.

  FIG. 7 shows a case where the light control unit 18 determines that the lighting ratios of the LEDs of the respective colors of the backlight block 15a are all 70%. That is, information that the lighting ratio of the LEDs of the LEDs 13a and 14a of the backlight 15a is 70% is stored in the lighting ratio storage unit 44 of the light control unit 18.

  The backlight control unit 19 reads this information from the lighting ratio storage unit 44 of the dimming unit 18, and further reads information stored in the analysis result storage unit 45.

  FIG. 8A shows information stored in the analysis result storage unit 45.

  The last pixel write voltage arrival time 45a indicates the time from when the display period of each color starts until the voltage written to the display element of the last pixel 78c reaches the voltage corresponding to each color of the display data. ing.

  The first pixel writing voltage leaving time 45b indicates the time from when the display period of each color starts until the voltage written to the display element of the first pixel 78a leaves from the voltage corresponding to each color of the display data. ing.

  The last pixel black insertion voltage arrival time 45c is from when the display period of each color starts until the voltage written in the display element of the last pixel 78c reaches a voltage corresponding to black for black insertion. Shows time.

  In the first embodiment, the voltage waveforms 75a, 75b, and 75c written to the display element of the first pixel 78a, the display element of the middle pixel 78b, and the display element of the last pixel 78c are actually used as testers. By analyzing the measured voltage waveforms 75a and 75c, the last pixel write voltage arrival time 45a, the first pixel write voltage departure time 45b, and the last pixel black insertion voltage arrival time shown in FIG. 45c was determined. Then, the obtained last pixel writing voltage arrival time 45a, first pixel writing voltage leaving time 45b, and last pixel black insertion voltage reaching time 45c are stored in advance in the analysis result storage unit 45 as shown in FIG. I remembered it.

  Then, the calculation unit 46 uses the backlight control signal (clock signal, horizontal synchronization signal, vertical synchronization signal, etc.) sent from the controller 4 to obtain the last pixel write voltage arrival time 45a, the first pixel write voltage. The lighting start time and lighting end of each of the red LED, green LED, and blue LED of the LEDs 13a and 14a of the backlight block 15a are calculated by using the leaving time 45b and the last pixel black insertion voltage arrival time 45c. The time is determined and stored in the time storage unit 47. Note that how to calculate the lighting start time and the lighting end time by the calculation unit 46 will be described later.

  FIG. 8B shows the lighting start timing and lighting end timing of each of the red LED, the green LED, and the blue LED among the LEDs 13 a and 14 a of the backlight block 15 a stored in the timing storage unit 47.

  In FIG. 8B, red LED lighting start timing 47a and red LED lighting end timing 47b indicate the lighting start timing and lighting end timing of the red LED of the LEDs 13a and 14a of the backlight block 15a, respectively. . In FIG. 8B, the green LED lighting start timing 47c and the green LED lighting end timing 47d are the green LED lighting start timing and lighting end timing of the LEDs 13a and 14a of the backlight block 15a, respectively. Show. In FIG. 8B, a blue LED lighting start timing 47e and a blue LED lighting end timing 47f indicate the lighting start timing and lighting end timing of the blue LED of the LEDs 13a and 14a of the backlight block 15a, respectively. ing.

  The backlight control unit 19 turns on the red LED of the LEDs 13a and 14a of the backlight block 15a at the timing when the red LED lighting start time 47a stored in the time storage unit 47 is reached. Then, the red LED of the LEDs 13a and 14a of the backlight block 15a is turned off at the timing when the red LED lighting end time 47b stored in the time storage unit 47 is reached. The backlight control unit 19 performs the same control for the green LED and the blue LED among the LEDs 13a and 14a of the backlight block 15a.

  Furthermore, the backlight control unit 19 also controls the luminance of the backlight block 15a when the LEDs 13a and 14a of the backlight block 15a are turned on. That is, when the backlight control unit 19 turns on the LEDs 13a and 14a of the backlight block 15a, the luminance of the backlight block 15a at the time elapsed from the start of the display period of each color is stored in the luminance table storage unit 48. This is determined using the stored brightness table. Then, the backlight block 15a is controlled so that the backlight block 15a is lit with the determined luminance.

  FIG. 8C shows a conceptual diagram of the luminance table stored in the luminance table storage unit 48. The horizontal axis in FIG. 8C indicates the time from the start time of the display period of each color, and the vertical axis corresponds to the luminance of the backlight block 15a. That is, the vertical axis indicates 1 when the backlight block 15a is turned on at the maximum luminance, indicates 0 when the backlight block 15a is turned off, and the intermediate luminance of the backlight block 15a is from 0 to 1. Shown numerically. That is, the luminance table stored in the luminance table storage unit 48 is a table that represents the luminance of the backlight block 15a at the time from the start time of the display period of each color as a numerical value from 0 to 1. is there.

  Therefore, the luminance of the backlight block 15a at the time elapsed from the start time of the display period of each color is a numerical value from 0 to 1 associated with the time from the luminance table stored in the luminance table storage unit 48. This can be obtained by multiplying the maximum luminance of the backlight block 15a by the value. A method for obtaining the brightness table stored in the brightness table storage unit 48 will be described later.

  When the backlight control unit 19 performs such control, in FIG. 7, among the LEDs 13a and 14a that are the light sources of the backlight block 15a, the red LED, the green LED, and the blue LED are turned on / off. , R_LED, G_LED, B_LED.

  In FIG. 7, R_LED, G_LED, and B_LED are illustrated as having constant luminance when lit, but this is because the first pixel 75a, The write voltage written to the display element of either the middle pixel 75b or the last pixel 75c has already reached an applied voltage such as a voltage corresponding to red, and during the lighting period of the backlight block 15a, This is because the writing voltage written to the display element of any pixel takes a constant value.

  For example, in FIG. 9 and the like, during the lighting period of the backlight block 15a, the luminance of the R_LED, G_LED, and B_LED changes according to the voltage written in the pixel display element. This will be described later.

  Now, as described above, how to calculate the lighting start time and the lighting end time by the calculation unit 46 will be described with reference to FIG.

  The calculation unit 46 reads from the lighting ratio storage unit 44 information that the lighting ratio of the LEDs 13a and 14a of the backlight block 15a is 70%. Next, the calculating part 46 calculates | requires the lighting period of red LED of LED13a of the backlight block 15a, 14a by multiplying the lighting ratio read from the lighting ratio memory | storage part 44 with respect to a red display period. The calculation unit 46 performs the same processing for green and blue, thereby obtaining the lighting period of the green LED and the lighting period of the blue LED of the LEDs 13a and 14a of the backlight block 15a.

  In addition, the lighting period of the red LED of this embodiment is an example of the predetermined lighting period of the present invention, and the lighting period of the green LED of this embodiment is an example of the predetermined lighting period of the present invention. The lighting period of the blue LED in this embodiment is an example of the predetermined lighting period of the present invention.

  Next, using the backlight control signal, the calculation unit 46 actually starts writing a voltage corresponding to the red color of the display data to the display element of the first pixel 78 shown in FIG. 7), and the final pixel write voltage arrival time 45a stored in the analysis result storage unit 45 is added at the determined time T0. In this way, the time T1 when the voltage written in the display element of the last pixel 78 reaches the red writing voltage 71 is obtained (see FIG. 7).

  Furthermore, the calculation unit 46 stores the analysis result storage unit 45 in the analysis result storage unit 45 at a time T0 (see FIG. 7) at which writing of the voltage corresponding to the red color of the display data is actually started on the display element of the first pixel 78a shown in FIG. The stored first pixel write voltage leaving time 45b is added. In this way, the time T2 (see FIG. 7) at which the voltage written to the display element of the first pixel 78a departs from the red writing voltage 71 is obtained.

  The calculation unit 46 uses the LEDs 13a and 14a that are the light sources of the backlight block 15a so that the time between the time T1 and the time T2, that is, the time (T1 + T2) / 2 coincides with the middle of the lighting period of the red LED. Among them, the lighting start timing and lighting end timing of the red LED are obtained and stored in the timing storage unit 47 as the red LED lighting start timing 47a and the red LED lighting end timing 47b, respectively.

  The calculation unit 46 performs the same processing on the green LED and the blue LED among the LEDs 13a and 14a that are the light sources of the backlight block 15a, thereby causing the timing storage unit 47 to store the green LED lighting start timing 47c, green The LED lighting end timing 47d, the blue LED lighting start timing 47e, and the blue LED lighting end timing 47f are stored in the timing storage unit 47.

  This completes the description of how to determine the lighting start time and lighting end time.

  Next, how to obtain the luminance table stored in the luminance table storage unit 48 will be described. The luminance table is obtained based on both the voltage waveform 75a written in the display element of the first pixel 78a and the voltage waveform 75c written in the display element of the last pixel 78c.

  That is, from the start of the red display period to the end of the black insertion period following the red display period, from the start of the red display period to the end of the black insertion period following the red display period The voltage waveform 75a written in the display element of the first pixel 78a and the voltage waveform 75c written in the display element of the last pixel 78c are measured in advance by a tester at each time elapsed since. Thus, the voltage waveform 75a written in the display element of the first pixel 78a and the display element of the last pixel 78c from the start time of the red display period to the end time of the black insertion period following the red display period. The obtained voltage waveform 75c is obtained.

  Next, a luminance table is created by analyzing the obtained voltage waveform. As described above, the luminance table stored in the luminance table storage unit 48 represents the luminance of the backlight block 15a at the time from the start time of the display period of each color as a numerical value from 0 to 1. It is a table.

  From the start time of the red display period to the end time of the black insertion period following the red display period, for the first half of the period, a luminance table is obtained based on the voltage waveform 75a written to the display element of the first pixel 78a, For the subsequent half period, a luminance table is obtained based on the voltage waveform 75c written to the display element of the last pixel 78c.

  That is, in the first half of the period from the start time of the red display period to the end time of the black insertion period following the red display period, the display of the first pixel 78a is performed at each time elapsed from the start time of the red display period. When the voltage written in the element reaches the voltage corresponding to red, the luminance for that time is set to 1. When the voltage written in the display element of the first pixel 78a at that time reaches the voltage corresponding to black, the luminance at that time is set to zero. Further, when the voltage written to the display element of the first pixel 78a at that time is an intermediate voltage between the voltage corresponding to red and the voltage corresponding to black, the written voltage corresponds to red. The closer the voltage is, the closer the brightness at that time is to 1, and the closer the written voltage is to the voltage corresponding to black, the closer the brightness at that time is to 0.

  In the latter half of the period from the start time of the red display period to the end time of the black insertion period following the red display period, writing is performed in the display element of the last pixel 78c at each time elapsed from the start time of the red display period. When the detected voltage reaches the voltage corresponding to red, the luminance at that time is set to 1. When the voltage written in the display element of the last pixel 78c at that time reaches the voltage corresponding to black, the luminance at that time is set to zero. Furthermore, when the voltage written in the display element of the last pixel 78c at that time is an intermediate voltage between the voltage corresponding to red and the voltage corresponding to black, the written voltage corresponds to red. The closer the voltage is, the closer the brightness at that time is to 1, and the closer the written voltage is to the voltage corresponding to black, the closer the brightness at that time is to 0.

  Such a value is obtained for each time elapsed from the start time of the red display period in the period from the start time of the red display period to the end time of the black insertion period following the red display period.

  Then, from the start time of the red display period to the end time of the black insertion period following the red display period, the time from the start time of the red display period corresponds to the value from 0 to 1 obtained as described above. And stored in the brightness table storage unit 48. As described above, the luminance table shown in FIG. 8C can be obtained.

  FIG. 9 shows the first pixel 78a and the middle pixel 78b when the lighting periods of the red LED, green LED, and blue LED are the longest among the LEDs 13a and 14a that are the light sources of the backlight block 15a. FIG. 6 is a timing chart showing voltage waveforms written in the display elements of the last pixel 76c and lighting / extinguishing states of LEDs of respective colors in the backlight block 15a. The reference numerals and the like are the same as those in FIG.

  However, in FIG. 9, the wavy lines in R_LED, G_LED, and B_LED indicate the lighting periods of the LEDs 13a and 14a of the respective colors of the backlight block 15a, and the solid lines indicate the luminance of the R_LED, G_LED, and B_LED.

  In FIG. 9, among the LEDs 13a and 14a that are the light sources of the backlight block 15a, the red LED is lit from the time T0 to the time T3, and the green LED is lit from the time T4 to the time T7. The blue LED is lit from time T8 to T11.

  The red display will be described. At time T3, the last pixel shown in FIG. 8A is displayed at time T0 when the writing of the voltage corresponding to the red color of the display data is actually started on the display element of the first pixel 78a. This is the time when the black insertion voltage arrival time 45c is added. That is, time T3 is a time when the voltage written in the display element of the last pixel 78c reaches a voltage corresponding to black for black insertion. Therefore, after time T3, until writing of a voltage corresponding to green is started on the display element of the first pixel 78a, all pixels in the portion of the liquid crystal display panel 10 facing the backlight block 15a correspond to black. Voltage is written. When the red LED is lit when the voltage corresponding to black is written in all the pixels of the portion of the liquid crystal display panel 10 facing the backlight block 15a, the power consumption of the red LED is only increased. It doesn't help at all. Furthermore, when the voltage corresponding to black is written in the pixel, if the transmittance of the display element of the pixel is not completely zero, it may cause a decrease in contrast.

  For the same reason, when the red LED is turned on in the past from the time T0, the power consumption of the red LED is increased and the contrast is also lowered.

  Therefore, as the upper limit when the dimming control unit 33 increases the lighting ratio of the red LED, it does not protrude from the range of the lighting period of the red LED in FIG. 9 (period from time T0 to time T3). did.

  Further, with respect to R_LED, the luminance of the backlight block 15a is continuously increased with time from the time T0 until the voltage written in the display element of the first pixel 75a reaches the voltage corresponding to red. It will increase. Then, after the voltage written in the display element of the first pixel 75a from time T0 reaches the voltage corresponding to red, the luminance of the backlight block 15a takes a constant value. The luminance of the backlight block 15a continuously decreases as time elapses from the time when the voltage written in the display element of the last pixel 75c leaves the voltage corresponding to red to the time T3. Go. The same applies to G_LED and B_LED.

  Such an operation can be realized as follows.

  That is, when the calculation unit 46 determines the red LED lighting start timing 47a by the above-described operation, if the red LED lighting start timing 47a is a time earlier than the timing T0, the red LED lighting is turned on. The start time 47a is made to coincide with the time T0. In addition, when the calculation unit 46 determines the red LED lighting end timing 47b by the operation described above, when the red LED lighting end timing 47b is a time later than the timing T3, the red LED lighting end timing 47b is determined. The lighting end time 47b is made to coincide with the time T3.

  For the green display, by performing the same process as the red display, the green LED lighting period protrudes from the range of the green LED lighting period (range from time T4 to time T7) in FIG. You can avoid it. For the blue display, by performing the same process as the red display, the blue LED lighting period is changed from the range of the blue LED lighting period (range from time T8 to time T11) in FIG. It can be prevented from protruding.

  Then, during the period from the time T0 to the time T3, which is the lighting period of the red LED of the backlight block 15a, the backlight control unit 19 uses the luminance table stored in the luminance table storage unit 48 described above. The luminance of the light block 15a is obtained, and the backlight control unit 19 controls the luminance of the backlight block 15a so as to match the obtained luminance, whereby a luminance waveform as shown by R_LED in FIG. 9 is obtained. By doing the same for the green LED and the blue LED of the backlight block 15a, the luminance waveforms as shown by G_LED and B_LED in FIG. 9 are obtained, respectively.

  FIG. 10 shows the first pixel 78a and the middle pixel when the lighting periods of the red LED, the green LED, and the blue LED among the LEDs 13a and 14a that are the light sources of the backlight block 15a are the shortest. FIG. 78 is a timing chart showing voltage waveforms written in the display elements of 78b and the last pixel 78c, and lighting / extinguishing states of LEDs of respective colors of the backlight block 15a. The reference numerals and the like are the same as those in FIG.

  In FIG. 10, among the LEDs 13a and 14a that are the light sources of the backlight block 15a, the red LED is lit from time T1 to time T2, and the green LED is lit from time T5 to time T7. The blue LED is lit from time T9 to T10. By setting the lighting ratio of each color, it is possible to realize the on / off state of each color LED in FIG. FIG. 10 shows an example in which the decrease in luminance is suppressed as much as possible by making the lighting period of the LEDs of the respective colors the longest within a range where no luminance difference occurs. In the first embodiment, the lighting ratio of each color is set so as not to be shorter than the lighting period of the LED of each color in FIG.

  Needless to say, the lighting ratio may be made smaller than the lighting ratio that is the lighting period of the LED of each color in FIG. 10 in order to improve the moving image visibility close to the impulse display such as CRT.

  Heretofore, how to calculate the lighting start time and the lighting end time by the calculation unit 46 has been described.

  The light control unit 18 stores a reference value for the backlight block 15a using the red luminance, the green luminance, and the blue luminance detected by the optical sensor unit 16a (see FIG. 2) constituting the optical sensor unit 26. The lighting ratio is determined so that the LEDs of the respective colors of the backlight block 15a match the reference luminance and / or chromaticity stored in the unit 40, and stored in the lighting ratio storage unit 44.

  By using the lighting ratio determined by dimming by the dimming unit 18 as described above, the calculation unit 46 described above determines the lighting start timing and lighting end timing of the LEDs of each color, so that the backlight block 15a is used as a reference. Dimming can be performed so as to match the reference luminance and / or chromaticity stored in the value storage unit 40.

  Further, by performing the same processing as described above for the backlight blocks 15b to 15e, it is possible to correct the luminance difference and chromaticity difference between the backlight blocks 15a to 15e. As a result, an optimal white balance can be maintained, and variations in light sources such as LEDs and color shifts during temperature changes can be suppressed.

  Further, in FIG. 7, the lighting ratio stored in the lighting ratio storage unit 44 increases by increasing the luminance stored in the reference value storage unit 40. In this way, when the lighting ratio stored in the lighting ratio storage unit 44 is increased to approach the lighting period of each LED shown in FIG. 9, the contrast decreases and the lighting period of each color LED becomes longer. Since the luminance increases, the luminance increases, and the luminance difference in the place increases. Therefore, when the liquid crystal display device 1 of the first embodiment increases the lighting ratio of the LEDs of the respective colors by increasing the lighting ratio and approaches the lighting period of each LED shown in FIG. Display with high brightness corresponding to the lighting period and brightness of the.

  In FIG. 7, the lighting ratio stored in the lighting ratio storage unit 44 decreases by decreasing the luminance stored in the reference value storage unit 40. In this way, when the lighting ratio stored in the lighting ratio storage unit 44 is decreased to approach the lighting period of each LED shown in FIG. 10, the contrast increases and the lighting period of each color LED decreases. As a result, the luminance decreases, and the luminance difference at the location decreases. Therefore, in the liquid crystal display device 1 of the first embodiment, a luminance difference is generated depending on the location of the display screen by reducing the lighting ratio and shortening the lighting period to approach the lighting period of each LED shown in FIG. This can be suppressed and display with high contrast is possible.

  As described above, by changing the setting of the reference luminance and / or chromaticity stored in the reference value storage unit 40 and increasing / decreasing the lighting ratio of each color LED, the liquid crystal according to the first embodiment is used. The display device 1 can freely dimm the degree of contrast of the display screen of the liquid crystal display panel 10, the magnitude of the luminance, and the degree of luminance difference as designed values.

  Furthermore, the liquid crystal display device 1 according to the first embodiment uses the luminance table stored in the luminance table storage unit 48 as described above, and uses the luminance table stored in the backlight block 15a during the lighting period of the backlight block 15a. Control brightness.

  As a result, as shown in the timing chart of FIG. 9, when the voltage written in the display element of the first pixel 75a has not yet reached the applied voltage corresponding to red, the voltage is applied to the display element of the first pixel 75a. As the written voltage approaches the applied voltage corresponding to red, the backlight control unit 19 controls so that the luminance of the backlight block 15a approaches the maximum luminance. Further, when the voltage written in the display element of the last pixel 75c deviates from the applied voltage corresponding to red, the voltage written in the display element of the last pixel 75c is separated from the applied voltage corresponding to red. The backlight control unit 19 controls the backlight block 15a so that the luminance of the backlight block 15a is further decreased from the maximum luminance. The same applies to the green display and the blue display.

  Thereby, when the applied voltage corresponding to each color is sufficiently written in the display element of the pixel, the backlight block 15a is lit at the maximum luminance, and the rise and fall of the voltage written in the pixel display element is increased. Regarding the portion, since the luminance of the backlight block 15a is controlled according to the level of the voltage written in the display element of the pixel, the consumption consumed by the liquid crystal display device 1 compared to the case where the luminance of the backlight block 15a is not controlled. The power can be reduced, and the optical performance of contrast and video response can be further improved.

  Further, as shown in FIG. 10, the liquid crystal display device 1 according to the first embodiment can reduce the lighting time of the LEDs 13a and 14a of the backlight block 15a, for example, when the lighting ratio is decreased. High contrast display can be performed. By utilizing this, the liquid crystal display device 1 of the first embodiment can be used for the purpose of efficiently lighting the LEDs 13a and 14a of the backlight block 15a.

  That is, by shortening the lighting time of the LEDs 13a and 14a of the backlight block 15a as much as possible and increasing the voltage supplied to the LEDs 13a and 14a of the backlight block 15a, the LEDs 13a and 14a and the like emit light with high brightness. Let In this way, the liquid crystal display device 1 can perform display with high contrast, and can further reduce power consumption.

  In the first embodiment, as shown in FIG. 2, the backlight 11 is divided into a plurality of backlight blocks 15 a to 15 e, so that the display screen can be displayed more than when the backlight 11 is not divided. The difference in brightness depending on the location is small, and high-contrast display is possible.

  In the first embodiment, the voltage waveforms 75a, 75b, and 75c of the display elements of the first pixel 78a, the middle pixel 78b, and the last pixel 78c are actually measured, and the measured voltage waveforms 75a and 75c are measured. Although it has been described that the last pixel write voltage arrival time 45a, the first pixel write voltage departure time 45b, and the last pixel black insertion voltage arrival time 45c shown in FIG. 8A are obtained by analysis, the present invention is not limited thereto. Absent.

  The last pixel writing voltage arrival time 45a, the first pixel writing voltage leaving time 45b, and the last pixel black insertion voltage reaching time 45c shown in FIG. 8A are the liquid crystal material used for the liquid crystal display panel 10 and the black insertion driving time. Therefore, the voltage corresponding to black is determined according to the timing of writing the voltage to the first pixel 78a, the last pixel 78c, and the like. Accordingly, the voltage waveform 75a of the display element of the first pixel 78a, based on the liquid crystal material to be used and the timing of writing the voltage corresponding to black for black insertion driving to the first pixel 78a, the last pixel 78c, etc. A voltage waveform 75c of the last pixel 78c is predicted, and from the predicted voltage waveforms 75a and 78c, the last pixel write voltage arrival time 45a, the first pixel write voltage leave time 45b, and the last shown in FIG. The pixel black insertion voltage arrival time 45c may be obtained.

  Furthermore, in the first embodiment, the voltage waveforms 75a and 75c of the display elements of the first pixel 78a and the last pixel 78c are actually measured, and the measured voltage waveforms 75a and 75c are shown in FIG. Although described as obtaining the luminance table, the present invention is not limited to this. As described above, the voltage waveforms 75a and 75c of the display elements of the first pixel 78a and the last pixel 78c are obtained by applying the voltage corresponding to the liquid crystal material used in the liquid crystal display panel 10 and black for black insertion driving to the first pixel. It is determined according to the timing of writing to 78a, the last pixel 78c, and the like. Accordingly, the voltage waveform 75a of the display element of the first pixel 78a, based on the liquid crystal material to be used and the timing of writing the voltage corresponding to black for black insertion driving to the first pixel 78a, the last pixel 78c, etc. The voltage waveform 75c of the last pixel 78c may be predicted, and the brightness table illustrated in FIG. 8C may be obtained in advance from the predicted voltage waveforms 75a and 78c.

  In the first embodiment, a method for determining the red LED lighting start time 47a, the red LED lighting end time 47b, etc. for the lighting period according to the lighting ratio determined by the dimming control unit 33, As an upper limit when the LED lighting ratio is increased, the method of preventing the red LED lighting period range (period from time T0 to time T3) in FIG. 9 from protruding has been described. Absent. The following first method and second method can also be used.

  First, the first method will be described. After the calculation unit 46 calculates the middle time between the time T1 and the time T2, that is, the time (T1 + T2) / 2, the time length from the time (T1 + T2) / 2 to the time T0 and the time (T1 + T2) / The ratio of the time length from 2 to the time T3 is the time length from the time (T1 + T2) / 2 to the red LED lighting start time 47a and the time from the time (T1 + T2) / 2 to the red LED lighting end time. The red LED lighting start timing 47a and the red LED lighting end timing 47b are determined so as to match the ratio with the time length up to 47b.

  Then, when the determined red LED lighting start timing 47a and red LED lighting end timing 47b are the past time from the time T0 and the future time from the time T3, respectively, the red LED lighting start timing 47a and The red LED lighting end time 47b is made to coincide with the time T0 and the time T3. By similarly processing the green LED and the blue LED, the lighting start timing and lighting end timing can be determined.

  The second method is to determine the red LED lighting start timing 47a, the red LED lighting end timing 47b, etc., either the method described in the first embodiment or the first method. To decide. Then, an upper limit of the lighting ratio is calculated in advance so that either the red LED lighting start timing 47a or the red LED lighting end timing 47b coincides with the timing T0 or the timing T3, and the dimming control unit 33 adjusts the lighting ratio. What is necessary is just to make it a lighting ratio not exceed the upper limit of the lighting ratio calculated | required previously, when lighting.

  In either case of using the first method or the second method, the backlight control unit 19 uses the luminance table stored in the luminance table storage unit 48 during the lighting period of each color. Thus, by controlling the luminance of the backlight blocks 15a to 15e, the power consumption consumed by the liquid crystal display device 1 can be further reduced as compared with the case where the luminance of the backlight blocks 15a to 15e is not controlled, and the contrast and video response The optical performance can be further improved.

(Second Embodiment)
Next, a second embodiment will be described.

  In the first embodiment, the liquid crystal display device of the field sequential type, which performs black insertion driving, and the driving method of the liquid crystal display device have been described. Also in the second embodiment, as in the first embodiment, a field sequential type liquid crystal display device that performs black insertion driving and a driving method of the liquid crystal display device will be described.

  In the liquid crystal display device according to the first embodiment, as described in the timing charts of FIGS. 7, 9, and 10, for example, the case where the voltage written to the display element of the pixel 78 reaches the red write voltage 71 will be described. did. That is, the case where the voltages written to the display elements of the first pixel 78a, the middle pixel 78b, and the last pixel 78c reach the writing voltage and black writing voltage of each color and take a substantially constant value for a predetermined time. did.

  On the other hand, the voltage written to the display element of the pixel may not completely reach the writing voltage for each color. In other words, when the field sequential method is adopted and black insertion driving is performed, a color filter is formed on the counter substrate, and the liquid crystal display device is operated at a very high speed compared to a liquid crystal display device without black insertion driving. Need to drive. For this reason, there may occur a case where the voltage written to the display element of the pixel does not completely reach the writing voltage of each color for the reason of designing the liquid crystal display device such as increasing the number of pixels of the liquid crystal display panel.

  In the second embodiment, such a case will be described.

  In the second embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The liquid crystal display device of the second embodiment is the same as the liquid crystal display device 1 of the first embodiment.

  That is, FIG. 1 is a block diagram showing the configuration of the liquid crystal display device 1 of the second embodiment.

  The backlight 11 is also shown in FIG. 2A and FIG. 2B as in the first embodiment.

  The optical sensor unit 26 is also shown in FIGS. 4 (a) and 4 (b), as in the first embodiment.

  Further, in the liquid crystal display device of the second embodiment, details of the illumination system such as the light control unit 18, the backlight control unit 19, and the backlight 11 are shown in FIG. 3 as in the first embodiment. .

  The backlight control unit 19 of FIG. 3 includes an analysis result storage unit 45, a calculation unit 46, a time storage unit 47, and a brightness table storage unit 48, which is the same as in the first embodiment. However, in the second embodiment, since the case where the voltage written to the display element of the pixel does not completely reach the writing voltage of each color is handled, the information stored in the analysis result storage unit 45 and the luminance table The method of creating the brightness table stored in the storage unit 48 is different from that of the first embodiment.

  That is, the analysis result storage unit 45 according to the second embodiment is configured so that the writing voltage written to the pixel becomes the closest to the voltage corresponding to each color of the display data after the writing of the pixel is started. A semiconductor memory for storing time. Further, the luminance table stored in the luminance table storage unit 48 of the second embodiment is created based on the voltage written in the display element of the middle pixel 78b shown in FIG. The rest is the same as in the first embodiment.

  Next, the operation of the liquid crystal display device 1 of the second embodiment will be described, and an embodiment of the liquid crystal display device of the present invention will be described focusing on the differences from the first embodiment.

  When the power source of the liquid crystal display device 1 is turned on, the liquid crystal display device 1 performs transfer driving as in the first embodiment.

  When the transfer driving is completed and the liquid crystal display device 1 can perform the display operation, the liquid crystal display device 1 starts the display operation.

  The operation in which the liquid crystal display device 1 writes the video display signal to the pixel has already been described in the first embodiment. That is, in one frame period (or one field period), a red display period, a black insertion period, a green display period, a black insertion period, a blue display period, and a black insertion period are provided in this order.

  Next, the operation of the illumination system such as the backlight 11 will be described.

  Note that the operation of the illumination system such as the backlight 11 will be described by focusing on the backlight block 15a constituting the backlight 11, as in the first embodiment, but also for the backlight blocks 15b to 15e. Since the operation is similar to that of the backlight block 15a, description of these operations is omitted.

  FIG. 11 shows voltage waveforms written in the display elements of the first pixel 78a, the middle pixel 78b, and the last pixel 78c shown in FIG. 6, and the ON / OFF states of the LEDs of the respective colors of the backlight block 15a. It is a timing chart figure. In FIG. 11, time elapses from the left side toward the right side as viewed in the drawing.

  Reference numeral 81a denotes a voltage waveform written to the display element of the first pixel 78a.

  81b is a voltage waveform written in the display element of the middle pixel 78b.

  81c is a voltage waveform written in the display element of the last pixel 78c.

  In FIG. 11, time has passed from the left side to the right side as viewed in the drawing.

  In FIG. 11, R_LED, G_LED, and B_LED respectively indicate the on / off state and brightness of the red LED, the green LED, and the blue LED among the LEDs 13a and 14a that are the light sources of the backlight block 15a. That is, in R_LED, G_LED, and B_LED, the dotted line indicates the on / off state of the red LED, the green LED, and the blue LED, and the solid line indicates the luminance.

  In FIG. 11, 74 indicates a black voltage for black insertion driving, 71 indicates a voltage corresponding to red of display data, 72 indicates a red writing voltage to be written to the pixel in the red display period, and 72 indicates Indicates the voltage corresponding to the green color of the display data, indicates the green write voltage to be written to the pixel during the green display period, 74 indicates the voltage corresponding to the blue color of the display data, and indicates the blue write to be written to the pixel during the blue display period The voltage is shown.

  FIG. 11 shows a case where the light control unit 18 determines that the lighting ratios of the LEDs of the respective colors of the backlight block 15a are all 70%. That is, information that the lighting ratio of the LEDs of the LEDs 13a and 14a of the backlight 15a is 70% is stored in the lighting ratio storage unit 44 of the light control unit 18.

  The backlight control unit 19 reads this information from the lighting ratio storage unit 44 of the dimming unit 18, and further reads information stored in the analysis result storage unit 45.

  FIG. 12A shows information stored in the analysis result storage unit 45.

  In the middle pixel writing voltage closest approach time 45d, the voltage written to the display element of the middle pixel 78b after the writing of the voltage corresponding to each color of the display data is started to the display element of the first pixel 78a is This is the time required to approach the voltage corresponding to each color of the display data. In the last pixel threshold voltage arrival time 45e, the voltage written to the display element of the last pixel 78c after the start of writing of the voltage corresponding to each color of the display data to the display element of the first pixel 78a is changed to each color. Is a time required to reach a predetermined ratio with respect to the write voltage. In the first pixel threshold voltage leaving time 45f, the voltage written in the display element of the first pixel 78a after the voltage writing corresponding to each color of the display data is started on the display element of the first pixel 78a is changed to each color. This is the time to leave a predetermined ratio with respect to the write voltage.

  In the second embodiment, the voltage waveforms 81a, 81b, 81c written to the display element of the first pixel 78a, the display element of the middle pixel 78b, and the display element of the last pixel 78c are actually used as testers. By analyzing the measured voltage waveforms 81a, 81b, 81c, the middle pixel write voltage closest approach time 45d, the last pixel threshold voltage arrival time 45e, and the first pixel threshold voltage shown in FIG. The withdrawal time 45f was determined.

  Then, the calculated middle pixel write voltage closest approach time 45d, last pixel threshold voltage arrival time 45e, and first pixel threshold voltage departure time 45f are stored in advance in the analysis result storage unit 45 as shown in FIG. I remembered it.

  Then, the calculation unit 46 uses the backlight control signal (clock signal, horizontal synchronization signal, vertical synchronization signal, etc.) sent from the controller 4, and the middle pixel writing voltage closest approach time 45d, the last pixel threshold value By using the voltage arrival time 45e and the first pixel threshold voltage leaving time 45f, the lighting start timing and lighting end of each of the red LED, the green LED, and the blue LED of the LEDs 13a and 14a of the backlight block 15a are calculated. The time is determined and stored in the time storage unit 47. Note that how to calculate the lighting start time and the lighting end time by the calculation unit 46 will be described later.

  FIG. 12B shows the lighting start timing and lighting end timing of each of the red LED, the green LED, and the blue LED among the LEDs 13 a and 14 a of the backlight block 15 a stored in the timing storage unit 47. FIG. 12B is the same as FIG. 8B described in the first embodiment.

  The backlight control unit 19 turns on the red LED of the LEDs 13a and 14a of the backlight block 15a at the timing when the red LED lighting start time 47a stored in the time storage unit 47 is reached. Then, the red LED of the LEDs 13a and 14a of the backlight block 15a is turned off at the timing when the red LED lighting end timing 47b stored in the timing storage unit 47 is reached. The backlight control unit 19 performs the same control for the green LED and the blue LED among the LEDs 13a and 14a of the backlight block 15a.

  Furthermore, the backlight control unit 19 also controls the luminance of the backlight block 15a when the LEDs 13a and 14a of the backlight block 15a are turned on. That is, when the backlight control unit 19 turns on the LEDs 13a and 14a of the backlight block 15a, the luminance of the backlight block 15a at the time elapsed from the start of the display period of each color is stored in the luminance table storage unit 48. This is determined using the stored brightness table. Then, the backlight block 15a is controlled so that the backlight block 15a is lit with the determined luminance.

  FIG. 12C shows a conceptual diagram of the luminance table stored in the luminance table storage unit 48. The horizontal axis of FIG.12 (c) shows the time from the start time of the display period of each color, and a vertical axis | shaft respond | corresponds to the brightness | luminance of the backlight block 15a. That is, the vertical axis indicates 1 when the backlight block 15a is turned on at the maximum luminance, indicates 0 when the backlight block 15a is turned off, and the intermediate luminance of the backlight block 15a is from 0 to 1. Shown numerically. That is, the luminance table stored in the luminance table storage unit 48 is a table that represents the luminance of the backlight block 15a at the time from the start time of the display period of each color as a numerical value from 0 to 1. is there.

  Therefore, the luminance of the backlight block 15a at the time elapsed from the start time of the display period of each color is a numerical value from 0 to 1 associated with the time from the luminance table stored in the luminance table storage unit 48. This can be obtained by multiplying the maximum luminance of the backlight block 15a by the value. A method for obtaining the brightness table stored in the brightness table storage unit 48 will be described later.

  When the backlight control unit 19 performs such control, in FIG. 11, among the LEDs 13a and 14a that are the light sources of the backlight block 15a, the red LED, the green LED, the blue LED are turned on and off, and the brightness is as follows. , R_LED, G_LED, and B_LED, respectively.

  Now, as described above, how to calculate the lighting start time and the lighting end time by the calculation unit 46 will be described with reference to FIG.

  The calculation unit 46 reads from the lighting ratio storage unit 44 information that the lighting ratio of the LEDs 13a and 14a of the backlight block 15a is 70%. Next, the calculating part 46 calculates | requires the lighting period of red LED of LED13a of the backlight block 15a, 14a by multiplying a lighting ratio with respect to a red display period (red writing). The calculation unit 46 performs the same processing for green and blue, thereby obtaining the lighting periods of the LEDs 13a and 14a of the backlight block 15a and the blue LEDs.

  In addition, the lighting period of the red LED of this embodiment is an example of the predetermined lighting period of the present invention, and the lighting period of the green LED of this embodiment is an example of the predetermined lighting period of the present invention. The lighting period of the blue LED in this embodiment is an example of the predetermined lighting period of the present invention.

  Next, the calculation unit 46 uses the backlight control signal to determine the time when writing of the voltage corresponding to the red color of the display data is actually started on the display element of the first pixel 78a shown in FIG. At the determined time, the middle pixel writing voltage closest approach time 45d stored in the analysis result storage unit 45 is added. In this way, the time T20 when the write voltage waveform 81b of the display element of the middle pixel 78b is closest to the red write voltage 71 is obtained (see FIG. 11).

  The calculating unit 46 performs back-up so that the timing when the write voltage waveform 81b of the display element of the middle pixel 78b is closest to the red write voltage 71 coincides with the middle of the lighting period of the red LED. Of the LEDs 13a and 14a, which are the light sources of the light block 15a, the red LED lighting start time and the lighting end time are obtained and stored in the time storage unit 47 as the red LED lighting start time 47a and the red LED lighting end time 47b, respectively. (See FIG. 12B).

  The calculation unit 46 performs the same process on the green LED and the blue LED among the LEDs 13a and 14a that are the light sources of the backlight block 15a, thereby obtaining the time T21 and the time T22, thereby obtaining the time storage unit 47. The green LED lighting start timing 47c, the green LED lighting end timing 47d, the blue LED lighting start timing 47e, and the green LED lighting end timing 47f are stored in the timing storage unit 47.

  The method for obtaining the lighting start time and the lighting end time by the calculation unit 46 has been described above.

  Next, how to obtain the luminance table stored in the luminance table storage unit 48 will be described. In the second embodiment, unlike the first embodiment, the luminance table is obtained based on the voltage written in the display element of the middle pixel 77b.

  That is, from the start time of the red display period to the end time of the black insertion period following the red display period, from the start time of the red display period to the end time of the black insertion period following the red display period, The voltage written in the display element of the middle pixel 78b at each time elapsed from the start time is measured in advance by a tester. Thus, the voltage waveform 81b written to the display element of the middle pixel 78b is obtained in the period from the start time of the red display period to the end time of the black insertion period following the red display period.

  Next, a luminance table is created by analyzing the obtained voltage waveform 81b. As described above, the luminance table stored in the luminance table storage unit 48 represents the luminance of the backlight block 15a at the time from the start time of the display period of each color as a numerical value from 0 to 1. It is a table.

  In the period from the start time of the red display period to the end time of the black insertion period following the red display period, a luminance table is obtained based on the voltage waveform 81b written to the display element of the middle pixel 78b.

  That is, the voltage written in the display element of the middle pixel 78b in each time elapsed from the start time of the red display period in the period from the start time of the red display period to the end time of the black insertion period following the red display period. However, when the voltage corresponding to red is reached, the luminance at that time is set to 1. Then, when the voltage written in the display element of the pixel 78b in the middle of the time reaches the voltage corresponding to black, the luminance at that time is set to zero. Further, when the voltage written in the display element of the pixel 78b in the middle of the time is an intermediate voltage between the voltage corresponding to red and the voltage corresponding to black, the written voltage corresponds to red. The closer the voltage is, the closer the brightness at that time is to 1, and the closer the written voltage is to the voltage corresponding to black, the closer the brightness at that time is to 0.

  Such a value is obtained for each time elapsed from the start time of the red display period in the period from the start time of the red display period to the end time of the black insertion period following the red display period.

  Then, in the period from the start time of the red display period to the end time of the black insertion period following the red display period, the value from 0 to 1 obtained as described above is the time elapsed from the start time of the red display period. Are stored in the brightness table storage unit 48. As described above, the luminance table shown in FIG. 12C can be obtained.

  In the second embodiment, as the luminance table, the luminance of the backlight block in each period of the period from the start time of the red display period to the end time of the subsequent black insertion period drawn in the red display period is set to the middle pixel. It has been described that it is obtained based on the voltage written in the display element 77b.

  Then, as a result of controlling the luminance of the backlight block 15a using the luminance table thus obtained, as shown in FIG. 11, FIG. 13, or FIG. 14, when the backlight block 15a starts to be lit. The luminance of the backlight block 15a increases to a certain luminance level instantaneously, and after reaching the peak luminance, changes gradually over time, and from the instantaneous luminance level at the lighting end timing of the backlight block 15a. It turned off.

  Hereinafter, a method for obtaining a luminance table different from the above will be described. When the luminance of the backlight block 15a is controlled using the luminance table obtained as described below, for example, the luminance of the backlight block 15a increases gradually rather than instantaneously at the lighting start time. After reaching the peak position of the backlight block 15a shown in FIG. 11, FIG. 13, or FIG. 14, it does not immediately turn off from a certain luminance level at the lighting end time, but gradually decreases until the lighting end time. It is also possible to make it.

  That is, from the start time of the red display period to the end time of the black insertion period following the red display period, from the start time of the red display period to the end time of the black insertion period following the red display period, The voltage written in the display element of the middle pixel 78b at each time elapsed from the start time is measured in advance by a tester. Thus, the voltage waveform 81b written to the display element of the middle pixel 78b is obtained in the period from the start time of the red display period to the end time of the black insertion period following the red display period.

  Next, by analyzing the obtained voltage waveform 81b, the time when the voltage waveform 81b takes a peak value is obtained.

  Since the time when the obtained peak value is taken coincides with the middle pixel writing voltage closest approach time 45d shown in FIG. 12A, the time when the obtained peak value is taken is the closest to the middle pixel writing voltage. The time 45d may be used.

  Next, a brightness table is created. In the luminance table, all values are set to 0 in the period up to the red LED lighting start time 47a. Then, during the period from the red LED lighting start time 47a to the time when the obtained peak value is obtained, the value of the luminance table is gradually increased from 0, and the value of the luminance table is obtained when the peak value is obtained. Is 1. Then, during the period from the time when the peak value is taken to the time when the red LED lighting end time 47b is reached, the luminance table is gradually reduced from 1 to 0. By creating the luminance table in this way, as described above, the luminance of the backlight block 15a gradually increases instead of instantaneously increasing at the lighting start timing, and from a certain luminance level at the lighting end timing. Instead of turning off the light instantaneously, it can be made to decrease gently until the lighting end time.

  In addition, as shown in FIG. 12B, there may occur a case where the lighting start timing and the lighting end timing of each color LED are different in the length of the period. In such a case, a brightness table may be created for each color, and the brightness table corresponding to displaying each color may be used.

  In the second embodiment, the luminance table is described based on the voltage written in the display element of the middle pixel 77b. However, the present invention is not limited to this.

  The luminance table may be determined from the average voltage of the voltage written in the display element of the first pixel 77a and the voltage written in the display element of the last pixel 77c.

  Further, the luminance table is calculated based on the average voltage of the voltage written in the first pixel 77a, the voltage written in the display element of the middle pixel 77b, and the voltage written in the display element of the last pixel 77a. You may decide the table.

  Alternatively, the luminance table may be determined from the average voltage of the voltages written on the display elements existing on the respective scanning lines from the first scanning line 77a to the last scanning line 77.

  In addition, among the scanning lines from the first scanning line 77a to the last scanning line 77c, every N scanning lines (N is an integer of 2 or more) are selected from the first scanning line 77a, and the luminance table exists on the selected scanning line. You may determine a brightness | luminance table from the average voltage of the voltage written in each display element.

  Of the scanning lines from the first scanning line 77a to the last scanning line 77c, M scanning lines are randomly selected (M is 2 or more and the scanning lines existing from the first scanning line 77a to the last scanning line 77c). It is also possible to select an integer smaller than the number of scanning lines and determine the luminance table from the average voltage of the voltages written in the respective display elements existing on the selected scanning line.

  As the reference luminance stored in the reference value storage unit 40 in FIG. 3 is increased, the backlight control block 33a is dimmed by the dimming control unit 33, and as a result, is stored in the lighting ratio storage unit 44. The lighting ratio is also increased.

  In FIG. 11, even when the lighting ratio increases in this way, the upper limit of the lighting period of each color LED is limited as follows.

  That is, when the red LED is described, it is assumed that the calculation unit 46 determines the red LED lighting start timing 47a and the red LED lighting end timing 47b by the operation as described above.

  Thereafter, when the red LED lighting start time 47a starts to write the voltage corresponding to the red color of the display data to the display element of the first pixel 78a, the last pixel threshold voltage arrival time 45e (see FIG. 12). ) Is added (corresponding to time T20L in FIG. 11, hereinafter referred to as time T20L).

  If the red LED lighting start time 47a is smaller than the time T20L (past), the red LED lighting start time 47a is made equal to the time T20L and stored in the time storage unit 47.

  If the red LED lighting start timing 47a is equal to or greater than the timing T20L (future), the red LED lighting start timing 47a is stored in the timing storage unit 47 without being changed.

  Furthermore, when the red LED lighting end time 47b starts to write the voltage corresponding to the red color of the display data to the display element of the first pixel 78a, the first pixel threshold voltage leaving time 45f (see FIG. 12). ) Is added (corresponding to time T20U in FIG. 11, hereinafter referred to as time T20U).

  If the red LED lighting end time 47b is equal to or greater than the time T20U (future), the red LED lighting end time 47b is made equal to the time T20U and stored in the time storage unit 47.

  If the red LED lighting end time 47b is smaller than the time T20U (past), the red LED lighting end time 47b is stored in the time storage unit 47 without being changed.

  Similar processing is performed for the green LED and the blue LED.

  Thus, even when the lighting ratio is increased by limiting the upper limit of the lighting period of the red LED, the green LED, and the blue LED among the LEDs 13a and 14a that are the light sources of the backlight block, An increase in power consumption of each color LED can be suppressed, and a decrease in contrast can be suppressed.

  Furthermore, as shown by R_LED in FIG. 11, when the backlight block 15a displays red, the luminance of the backlight block 15a continuously increases as time elapses from the time when the backlight block 15a starts to light. Eventually, the backlight block 15a eventually reaches the maximum luminance at time T20. Thereafter, the luminance of the backlight block 15a continuously decreases as time elapses until the lighting end timing. When the backlight block 15a displays green and blue, they are indicated by G_LED and B_LED in FIG. 11, respectively, and the luminance of the backlight block 15a changes in the same manner as when the backlight block 15a displays red.

  As described above, with respect to the rising and falling portions of the voltage written to the display element of the middle pixel 75b, the backlight control unit 19 performs the backlight block based on the voltage written to the display element of the middle pixel 75b. Since the luminance of 15a is controlled, the power consumption consumed by the liquid crystal display device 1 can be further reduced as compared with the case where the luminance of the backlight block 15a is not controlled, and the optical performance of contrast and moving image response can be further improved.

  FIG. 13 shows a case where the light control unit 18 determines so that the lighting ratios of the LEDs of the respective colors of the backlight block 15a are all 100%. In other words, the lighting ratio storage unit 44 of the light control unit 18 stores information that the lighting ratios of the LEDs of the LEDs 13a and 14a of the backlight 15a are 100%. Even in such a case, by performing the same operation as described above, the calculation unit 46 can obtain the red LED lighting start timing 47a, the red LED lighting end timing 47b, and the like shown in FIG. 8B. I can do it.

  FIG. 14 shows a case where the light control unit 18 determines that the lighting ratios of the LEDs of the respective colors of the backlight block 15a are all 30%. That is, the lighting ratio storage unit 44 of the light control unit 18 stores information that the lighting ratio of the LEDs of the LEDs 13a and 14a of the backlight 15a is 30%. Even in such a case, by performing the same operation as described above, the calculation unit 46 can obtain the red LED lighting start time 47a, the red LED lighting end time 47b, and the like shown in FIG. I can do it.

  As shown in FIG. 14, even when the lighting ratio is lowered to 30%, that is, when the time during which the LEDs 13a and 14a of the backlight block 15a are lit is shortened, the middle scanning line 77b shown in FIG. The timings T20, T21, T22 at which the middle pixel 78b (see FIG. 6) approaches the red writing voltage 71, the green writing voltage 72, and the blue writing voltage 73 respectively coincide with the center of the lighting period of the backlight block 15a. . Then, the time when the first pixel 78a of the first scanning line 77a shown in FIG. 6 is closest to the red writing voltage 71, the green writing voltage 72, and the blue writing voltage 73, respectively, of the LEDs 13a and 14a of the backlight block 15a. It is included in the period when the red LED, the green LED, and the blue LED are lit. Similarly, when the last pixel 78c of the last scanning line 77c shown in FIG. 6 is closest to the red writing voltage 71, the green writing voltage 72, and the blue writing voltage 73, respectively, the LEDs 13a and 14a of the backlight block 15a. The red LED, the green LED, and the blue LED are included in a period for lighting. As shown in FIGS. 11 and 13, the same applies to the case where the lighting ratio is larger than that in FIG.

  Therefore, even when the voltage waveform written to the display element of the pixel is different from that of the first embodiment, the same effect as that of the first embodiment can be obtained. In particular, with respect to the rising and falling portions of the voltage written in the display element of the middle pixel 75b, the backlight control unit 19 determines whether the backlight block 15a has a voltage based on the voltage written in the display element of the middle pixel 75b. Since the luminance is controlled, the power consumption consumed by the liquid crystal display device 1 can be further reduced as compared with the case where the luminance of the backlight block 15a is not controlled, and the optical performance of contrast and moving image response can be further improved.

  Further, in the liquid crystal display device 1 of the second embodiment, as shown in FIG. 14, when the lighting ratio is lowered to 30%, the time during which the LEDs 13a and 14a of the backlight block 15a are lit is shortened. Even in this case, display with high contrast can be performed.

  By utilizing this, the liquid crystal display device 1 of the second embodiment can be used for the purpose of efficiently lighting the LEDs 13a and 14a of the backlight block 15a.

  That is, by shortening the lighting time of the LEDs 13a and 14a of the backlight block 15a and increasing the voltage supplied to the LEDs 13a and 14a of the backlight block 15a, the LEDs 13a and 14a and the like emit light with high luminance. In this way, the liquid crystal display device 1 can perform high-contrast display and can be close to an impulse-type display such as a CRT, so that the video visibility can be improved and the power consumption can be further increased. Can also be reduced.

  In the second embodiment, the voltage waveforms 81a, 81b, 81c of the display elements of the first pixel 78a, the middle pixel 78b, and the last pixel 78c are actually measured, and the measured voltage waveforms 81a, 81b are measured. , 81c, the middle pixel writing voltage closest approach time 45d, the last pixel threshold voltage arrival time 45e, and the first pixel threshold voltage leaving time 45f shown in FIG. Not limited to this.

  The middle pixel writing voltage closest approach time 45d, the last pixel threshold voltage arrival time 45e, and the first pixel threshold voltage departure time 45f are voltages corresponding to the liquid crystal material used for the liquid crystal display panel 10 and black for black insertion driving. Is determined according to the timing of writing the first pixel 78a, the middle pixel 78b, and the last pixel 78c. Accordingly, the first pixel 78a, the middle pixel 78b, based on the timing of writing the liquid crystal material to be used and the voltage corresponding to black for black insertion driving to the first pixel 78a, the middle pixel 78b, the last pixel 78c, etc. The voltage waveform of the display element of the last pixel 78c is predicted, and the middle pixel writing voltage closest approach time 45d, the last pixel threshold voltage arrival time 45e, and the first pixel threshold voltage leaving time 45f are obtained in advance from the predicted voltage waveform. Is also possible.

  Furthermore, in the second embodiment, it is assumed that the voltage waveform 81b actually written to the display element of the middle pixel 78b is actually measured and the luminance table shown in FIG. 8C is obtained from the measured voltage waveform 81b. However, it is not limited to this. As described above, the voltage waveform 75b of the display element of the middle pixel 78b corresponds to the liquid crystal material used in the liquid crystal display panel 10 and the timing of writing the voltage corresponding to black for black insertion driving to the middle pixel 78b. It is determined. Accordingly, the voltage waveform 75b of the display element of the middle pixel 78b is predicted based on the liquid crystal material to be used and the timing of writing the voltage corresponding to black for black insertion driving to the middle pixel 78b, and the predicted voltage waveform. The brightness table shown in FIG. 12C may be obtained in advance from 75b.

  Further, in the second embodiment, the calculation unit 46 turns on the red LED at time T20, that is, when the write voltage waveform 81b of the display element of the middle pixel 78b is closest to the red write voltage 71. Although it has been described that the red LED lighting start timing and lighting end timing are obtained among the LEDs 13a and 14a that are the light sources of the backlight block 15a so as to coincide with the middle of the period, the present invention is not limited to this.

  The calculation unit 46 determines the magnitude and fall of the rising slope of the display element of the middle pixel 78b at the time T20, that is, the time when the write voltage waveform 81b of the display element of the middle pixel 78b is closest to the red writing voltage 71. Of the LEDs 13a and 14a, which are the light sources of the backlight block 15a, the red LED lighting start timing and lighting end timing may be corrected in accordance with the ratio to the magnitude of the inclination. Moreover, you may correct | amend the lighting start time and lighting end time of each of green LED and blue LED among LED13a and 14a which are the light sources of the backlight block 15a similarly to red LED.

  For example, in FIG. 14, the magnitude of the slope on the left side of the time T20 of the voltage waveform 81b is smaller than the magnitude of the slope on the right side of the time T20 of the voltage waveform 81b. In such a case, first, the timing T20, that is, the timing T20 at which the writing voltage waveform 81b of the display element of the middle pixel 78b is closest to the red writing voltage 71 coincides with the middle of the lighting period of the red LED. Furthermore, the lighting start timing and lighting end timing of the red LED among the LEDs 13a and 14a which are the light sources of the backlight block 15a are obtained.

  Thereafter, the lighting of the red LED determined in accordance with the ratio of the left slope (falling slope) of the voltage waveform 81b at the time T20 and the right slope (rising slope) of the time T20 is started. The timing and lighting end timing can be corrected.

  In the case of FIG. 14, the magnitude of the left slope (falling slope) at time T20 is smaller than the magnitude of the right slope (rise slope) at time T20. In such a case, in FIG. 14, the lighting start timing and lighting end timing of the red LED are set to the lighting start timing of the red LED in accordance with the ratio between the magnitude of the falling slope and the magnitude of the rising slope. And the lighting end time is shifted to the left side.

  In this way, the obtained lighting start timing and lighting end timing of the red LED are set to a ratio between the magnitude of the falling slope at time T20 of the voltage waveform 81b and the magnitude of the rising slope at time T20 of the voltage waveform 81b. It can be corrected accordingly. The same applies to the green LED and the blue LED among the LEDs 13a and 14a which are the light sources of the backlight block 15a.

  In this way, display with higher contrast becomes possible.

  As another method for obtaining the lighting start timing and lighting end timing of the red LED, the voltage waveform 81b in FIG. 14 is obtained by integrating the time from the lighting start timing of the red LED to the lighting end timing of the red LED. It is also possible to determine the lighting start timing and lighting end timing of the red LED so that the area to be taken has an extreme value. However, the length (time) of the section in which the voltage waveform 81b is integrated is matched with the lighting period of the red LED and integrated. The same applies to the green LED and the blue LED. Even in this case, high contrast display is possible as in the second embodiment.

  Such processing can also be applied to the voltage waveform 75b described with reference to FIG. 7 of the first embodiment. However, in the voltage waveform 75b, the extreme value may not be uniquely determined depending on the time length of the lighting period of the red LED. For example, as shown in FIG. 10, when the time length of the lighting period of the red LED is shortened, the extreme value may not be uniquely determined. As described above, when the extreme value is not uniquely determined, the lighting start timing and lighting end timing of the red LED may be determined by the method described in the first embodiment.

  In this way, the lighting of the red LED is started so that the area obtained by integrating the voltage waveform 81b and the voltage waveform 75b with the time from the lighting start timing of the red LED to the lighting end timing of the red LED becomes an extreme value. By determining the timing and the lighting end timing, and performing the same processing for the green LED and the blue LED, it is possible to display high contrast as in the first and second embodiments. .

(Third embodiment)
Next, a third embodiment will be described.

  The temperature of the liquid crystal display panel is usually not constant due to the influence of ambient temperature fluctuations, heat generation of the liquid crystal display device itself, and the like. The voltage waveforms 75a, 75b, and 75c shown in FIG. 7 described in the first embodiment, the voltage waveforms 81a, 81b, and 81c shown in FIG. 11 described in the second embodiment, etc. It changes with influence.

  Therefore, in the third embodiment, a liquid crystal display device that can cope with a change in temperature of the liquid crystal display panel will be described focusing on differences from the first embodiment and the second embodiment.

  FIG. 15 is a block diagram illustrating a configuration of a liquid crystal display device 1 ′ according to the third embodiment. The difference between the first embodiment and the second embodiment is that the liquid crystal display device 1 of the first and second embodiments includes the backlight control unit 19, whereas the third embodiment is different from the third embodiment. The liquid crystal display device 1 ′ of the embodiment is provided with a backlight control unit 19 ′, and the liquid crystal display device 1 ′ of the third embodiment is further provided with a temperature sensor 27.

  The temperature sensor 27 is a sensor that is attached to the substrate on which the liquid crystal display panel 10 is formed and detects the temperature.

  FIG. 16 is a block diagram illustrating a configuration of the backlight control unit 19 ′ according to the third embodiment.

  The backlight control unit 19 ′ of the third embodiment obtains the temperature of the liquid crystal display panel 10 from the brightness table storage unit 48 ′ that stores a brightness table according to the temperature and the temperature detected by the temperature sensor 27. A luminance table selection unit 28 that selects a luminance table corresponding to the temperature of the liquid crystal display panel 10 from the luminance table storage unit 48 ′ is provided. Other than this, the backlight control unit 19 ′ of the third embodiment is the same as the backlight control unit 19 of the first and second embodiments.

  Next, the liquid crystal display device 1 'according to the third embodiment of the present invention and the driving method of the liquid crystal display device according to one embodiment of the present invention are different from the first and second embodiments. The explanation will focus on the points.

  In FIG. 17A, when the voltage corresponding to black is written in the display element of the pixel, when the voltage corresponding to white is written in the display element of the pixel, which voltage is written in the display element of the pixel. It is a figure which shows how it changes.

  In FIG. 17A, reference numerals 50a, 50b, and 50c denote voltage waveforms written in the display elements of the pixels when the temperature of the liquid crystal display panel 10 is 80 degrees Celsius, 50 degrees Celsius, and 20 degrees Celsius, respectively. The voltage waveform 50a written to the pixel display element in the case of 80 degrees Celsius reaches the voltage corresponding to white at time Q1, and the voltage waveform 50b written to the pixel display element in the case of 50 degrees Celsius is The voltage corresponding to white is reached at time Q2, and the voltage waveform 50c written to the display element of the pixel at 20 degrees Celsius reaches the voltage corresponding to white at time Q3.

  FIG. 17B shows the voltage written to the pixel display element when the voltage corresponding to black is written to the pixel display element when the voltage corresponding to white is written to the pixel display element. It is a figure which shows how is changed.

  In FIG. 17B, reference numerals 51a, 51b, and 51c denote voltage waveforms written in the display elements of the pixels when the temperature of the liquid crystal display panel 10 is 80 degrees Celsius, 50 degrees Celsius, and 20 degrees Celsius, respectively. The voltage waveform 51a written in the pixel display element in the case of 80 degrees Celsius reaches the voltage corresponding to white at time Q4, and the voltage waveform 51b written in the pixel display element in the case of 50 degrees Celsius is A voltage corresponding to white is reached at time Q5, and the voltage waveform 51c written to the display element of the pixel at 20 degrees Celsius reaches a voltage corresponding to white at time Q6.

  As is apparent from FIGS. 17A and 17B, as the temperature of the liquid crystal display panel 10 decreases, the voltage written to the pixel display element starts to be written to the pixel display element. The time to reach the target write voltage is increasing. This is because the viscosity of the liquid crystal increases as the temperature of the liquid crystal display panel 10 decreases.

  Therefore, in the third embodiment, a plurality of luminance tables are stored in advance for each temperature of the liquid crystal display panel 10 in the luminance table storage unit 48 ′ shown in FIG. 16.

  FIG. 18 (a), FIG. 18 (b), and FIG. 18 (c) show an example of a luminance table corresponding to the temperature. 18A is a schematic diagram of a luminance table when the temperature of the liquid crystal display panel 10 is 80 degrees Celsius, and FIG. 18B is a luminance table when the temperature of the liquid crystal display panel 10 is 50 degrees Celsius. FIG. 18C is a schematic diagram of a luminance table when the temperature of the liquid crystal display panel 10 is 20 degrees Celsius.

  The method for obtaining the luminance table for each temperature shown in FIG. 18A and the like is obtained in the same manner as the method for obtaining the luminance table described in the first embodiment or the second embodiment at each temperature. That's fine.

  The luminance table selection unit 28 selects a luminance table corresponding to the temperature of the liquid crystal display panel 10 detected by the temperature sensor 27 from the luminance table for each temperature stored in the luminance table storage unit 48 ′.

  The backlight control unit 19 ′ controls turning on / off of the backlight block 15a and the like and the luminance table selected by the luminance table selecting unit 28, as in the first embodiment or the second embodiment. Is used to control the luminance of the backlight block 15a as in the first or second embodiment.

  By doing so, the liquid crystal display device 1 ′ of the third embodiment has the same effect as the first embodiment or the second embodiment even if the temperature of the liquid crystal display panel 10 changes. Can be demonstrated.

  In the first to third embodiments, the OCB mode liquid crystal is used for the liquid crystal layer of the liquid crystal display panel 10. However, 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 first embodiment, the liquid crystal display device 1 according to the second embodiment, and the liquid crystal display device 1 ′ according to the third embodiment are conventional. As in the case of the liquid crystal display device 101, the field sequential type liquid crystal display device using the OCB mode liquid crystal display element has been described. 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, as described above, this is because the liquid crystal display panel 10 of the liquid crystal display device 1 of the first embodiment or the liquid crystal display panel 10 of the second embodiment or the liquid crystal display panel of the third embodiment. 10 is not limited to the one using the OCB mode liquid crystal, and the liquid crystal display panel 10 of the liquid crystal display device 1 of the first embodiment or the liquid crystal display panel 10 of the second embodiment or The liquid crystal display panel 10 of the third embodiment is not limited to a field sequential type liquid crystal display panel.

  As the liquid crystal display panel 10 of the liquid crystal display device 1 of the first embodiment, the liquid crystal display panel 10 of the liquid crystal display device 1 of the second embodiment, or the liquid crystal display panel 10 of the third embodiment, TN In the case of performing black insertion driving using a liquid crystal display panel using a liquid crystal layer that does not require reverse transition prevention driving, such as a (Twisted Nematic) alignment liquid crystal display panel, the first embodiment and the second embodiment are also performed. The third embodiment and the third 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 first embodiment and the second embodiment. The rest is the same as in the first embodiment or the second embodiment.

  Needless to say, the first embodiment, the second embodiment, and the third embodiment can be applied to a liquid crystal display device in which a color filter is formed on a counter substrate instead of the field sequential method.

  In the case of such a liquid crystal display device, in the above description, it is read that one frame (or one field period) is composed of a red display period (red writing) and a subsequent black insertion period (black writing). Further, if the red display period (red writing) is replaced with the display period (color writing), the above description can be applied as it is.

  Further, in the liquid crystal display device 1 of the first embodiment, the liquid crystal display device 1 of the second embodiment, and the liquid crystal display device 1 ′ of the third embodiment, red writing, black insertion, green writing, black Although the liquid crystal display panel 10 has been described as being driven in the order of insertion, blue writing, and black insertion, the present invention is not limited to this.

  Also when the liquid crystal display panel 10 is driven in the order of red writing, green writing, blue writing, and black insertion, the first embodiment, the second embodiment, and the third embodiment can be applied. . In this way, by reducing the black insertion period once in one frame (or one field) period, each period of red writing, green writing, and blue writing can be lengthened, so that high luminance display is possible. become.

  Also, when black insertion is performed only once before (past) or behind (future) any one of red writing, green writing, and blue writing, high-luminance display can be performed as described above. Further, when black insertion is performed in any two periods of red writing, green writing, and blue writing, high-luminance display can be performed in the same manner as described above.

  Further, when performing field sequential display 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, that is, red writing, green writing, blue Even when the liquid crystal display panel 10 is driven in the order of writing and black insertion is not performed, the first embodiment, the second embodiment, and the third embodiment can be applied.

  In the first embodiment or the second embodiment, the backlight control unit 19 has been described as controlling the luminance of the backlight blocks 15a to 15e using the luminance table storage unit 48. The control of the luminance of the backlight blocks 15a to 15e can be realized by any one of the following first to fourth methods.

  First, as described in the first embodiment and the second embodiment, the first luminance control method determines the red LED lighting start timing 47a, the red LED lighting end timing 47b, etc. In this method, the voltage supplied to light the red LED is kept constant during the lighting period of the LED, and the current is varied according to the value from 0 to 1 obtained from the luminance table. The same operation is performed for the green LED and the blue LED.

  In addition, as described in the first embodiment and the second embodiment, the second brightness control method determines the red LED lighting start timing 47a, the red LED lighting end timing 47b, and the like. This is a method in which the current supplied for lighting the red LED is kept constant during the lighting period of the red LED, and the voltage is varied according to the value from 0 to 1 obtained from the luminance table. The same operation is performed for the green LED and the blue LED.

  In addition, as described in the first embodiment and the second embodiment, the third luminance control method determines the red LED lighting start timing 47a, the red LED lighting end timing 47b, and the like. This is a method of varying both the current and voltage supplied to light the red LED according to the values from 0 to 1 obtained from the luminance table during the lighting period of the red LED. The same operation is performed for the green LED and the blue LED.

  In addition, as described in the first embodiment and the second embodiment, the fourth brightness control method determines the red LED lighting start timing 47a, the red LED lighting end timing 47b, and the like. During the lighting period of the red LED, the red LED is controlled by PWM (Pulse Width Modulation) with a cycle (very high frequency) shorter than the lighting cycle of the red LED, and 0 to 1 obtained from the luminance table This is a method of varying the duty of the PWM signal in accordance with the value of. The same operation is performed for the green LED and the blue LED.

  By using any one of the first to fourth luminance control methods, the backlight control unit 19 in the lighting period of the backlight blocks 15a to 15e is based on the voltage written in the display element of the pixel. The brightness of the backlight blocks 15a to 15e can be controlled.

  In the third embodiment, it goes without saying that the luminance control of the backlight blocks 15a to 15e can be realized by any one of the first to fourth methods.

  Furthermore, in the first embodiment and the second embodiment, the dimming control unit 33 determines the lighting ratio based on the reference luminance and / or luminance stored in the reference value storage unit 40. And stored in the lighting ratio storage unit 44. And based on the lighting ratio memorize | stored in the lighting ratio memory | storage part 44, the calculating part 46 determines the lighting period of LED of each color, and also the lighting start time and lighting end time about the determined lighting period of LED of each color However, the present invention is not limited to this.

  For example, in the first embodiment, red display in FIG. 7 will be described. When the calculation unit 46 determines the time (T1 + T2) / 2 in FIG. 7, the determined time (T1 + T2) / 2 is held. To do. Then, the calculation unit 46 may determine the red LED lighting start time 47a and the red LED lighting end time 47b with reference to the held time (T1 + T2) / 2. The same applies to the green LED and the blue LED. As described above, once the time (T1 + T2) / 2 is determined, it is necessary to calculate the time (T1 + T2) / 2 again every frame (or one field) period by holding the time. Therefore, the calculation amount in the calculation unit 46 can be reduced.

  In the second embodiment, the display of red in FIG. 11 will be described. When the calculation unit 46 determines the time T20 in FIG. 11, the determined time T20 is held. Then, the calculation unit 46 may determine the red LED lighting start time 47a and the red LED lighting end time 47b with reference to the held time T20. The same applies to the green LED and the blue LED. As described above, once the time T20 is determined, the time T20 is held, so that it is not necessary to recalculate the time T20 or the like every frame (or one field) period. Can be reduced.

  Further, in the first and second embodiments, the light source of the backlight 11 has 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 is used as the light source of the backlight 11. It doesn't matter. Further, a display device using an EL element may be used as the light source of the backlight 11. In short, it is only necessary to use a light source having high-speed response as the light source of the backlight 11.

  Further, in the first and second embodiments, it has been described that one LED is provided as a light source of the backlight 11 on each side of each backlight block, but the present invention is not limited to this. Each backlight block may be provided on one side. In this case, the optical sensor unit 26 may be provided on the side opposite to the side where the LEDs are provided.

  Furthermore, in the first and second embodiments, the backlight 11 is divided into five backlight blocks 15a to 15e. However, the present invention is not limited to this. The backlight 11 may not be divided into a plurality of backlight blocks, but may be composed of only one backlight. Further, the backlight 11 may be divided into two or more backlight blocks, and may be divided into at least the 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. . 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.

  The program of the present invention is a program for causing a computer to execute the functions of all or part of the liquid crystal display device of the present invention described above, and is a program that operates in cooperation with the computer.

  The recording medium of the present invention is a recording medium that records a program for causing a computer to execute all or part of the functions of the liquid crystal display device of the present invention described above. It is a recording medium that can be read and the read program executes the function in cooperation with the computer.

  In addition, the above-mentioned “parts and the like” of the present invention means one or several parts of the plurality of parts.

  Further, the above-mentioned “functions of the parts” of the present invention means functions of all or a part of the parts.

  Further, one use form of the program of the present invention may be an aspect in which the program is recorded on a recording medium such as a ROM readable by a computer and operates in cooperation with the computer.

  Also, one use form of the program of the present invention is an aspect in which the program is transmitted through a transmission medium such as the Internet, a transmission medium such as light, radio wave, and sound wave, read by a computer, and operates in cooperation with the computer. Also good.

  The computer of the present invention described above is not limited to pure hardware such as a CPU, but may include firmware, an OS, and peripheral devices.

  As described above, the configuration of the present invention may be realized by software or hardware.

  The liquid crystal display device, the driving method of the liquid crystal display device, the program, and the recording medium according to the present invention have an effect of suppressing a decrease in contrast, and a liquid crystal display including a backlight that illuminates the liquid crystal display panel It is useful for a device, a driving method of a liquid crystal display device, a program, a recording medium, and the like.

  In addition, the liquid crystal display device, the driving method of the liquid crystal display device, the program, and the recording medium according to the present invention have an effect of suppressing a reduction in moving image response, and provide a backlight for illuminating the liquid crystal display panel. It is useful for a liquid crystal display device, a driving method of the liquid crystal display device, a program, a recording medium, and the like.

  In addition, the liquid crystal display device, the driving method of the liquid crystal display device, the program, and the recording medium according to the present invention have an effect that power consumption can be reduced, and the liquid crystal having a backlight that illuminates the liquid crystal display panel It is useful for a display device, a driving method of a liquid crystal display device, a program, a recording medium, and the like.

The block diagram which shows the structure of the liquid crystal display device in the 1st and 2nd embodiment of this invention (A) A plan view showing an outline of a backlight used in the liquid crystal display device according to the first and second embodiments of the present invention. (B) The liquid crystal display device according to the first and second embodiments of the present invention. Side view showing the outline of the backlight used The block diagram which shows the detailed structure of the illumination system of the liquid crystal display device in the 1st and 2nd embodiment of this invention (A) The top view which shows the outline | summary of the optical sensor part used for the liquid crystal display device in the 1st-3rd embodiment of this invention (b) The liquid crystal display device in the 1st-3rd embodiment of this invention Sectional view showing the outline of the optical sensor used in Equivalent circuit showing the configuration of the pixel of the liquid crystal display device in the first to third embodiments of the present invention The figure which shows the relationship between the backlight block in the 1st-3rd embodiment of this invention, and the part of the display area of the liquid crystal display panel facing a backlight block. The voltage written in the display element of the specific pixel on the specific scan line among the scan lines existing in the display area of the liquid crystal display panel facing the backlight block of the liquid crystal display device in the first embodiment of the present invention Timing chart showing waveforms and lighting / unlit state of each color of backlight block (A) The figure which shows the information memorize | stored in the analysis result memory | storage part in the 1st Embodiment of this invention (b) The information memorize | stored in the time memory | storage part in the 1st Embodiment of this invention is shown (C) The figure which shows the information memorize | stored in the brightness | luminance table memory | storage part in the 1st Embodiment of this invention The voltage written in the display element of the specific pixel on the specific scan line among the scan lines existing in the display area of the liquid crystal display panel facing the backlight block of the liquid crystal display device in the first embodiment of the present invention Timing chart showing waveforms and lighting / unlit state of each color of backlight block The voltage written in the display element of the specific pixel on the specific scan line among the scan lines existing in the display area of the liquid crystal display panel facing the backlight block of the liquid crystal display device in the first embodiment of the present invention Timing chart showing waveforms and lighting / unlit state of each color of backlight block The voltage written in the display element of the specific pixel on the specific scan line among the scan lines existing in the display area of the liquid crystal display panel facing the backlight block of the liquid crystal display device according to the second embodiment of the present invention Timing chart showing waveforms and lighting / unlit state of each color of backlight block (A) The figure which shows the information memorize | stored in the analysis result memory | storage part in the 2nd Embodiment of this invention (b) The information memorize | stored in the time memory | storage part in the 2nd Embodiment of this invention is shown (C) The figure which shows the information memorize | stored in the brightness | luminance table memory | storage part in the 2nd Embodiment of this invention. The voltage written in the display element of the specific pixel on the specific scan line among the scan lines existing in the display area of the liquid crystal display panel facing the backlight block of the liquid crystal display device according to the second embodiment of the present invention Timing chart showing waveforms and lighting / unlit state of each color of backlight block The voltage written in the display element of the specific pixel on the specific scan line among the scan lines existing in the display area of the liquid crystal display panel facing the backlight block of the liquid crystal display device according to the second embodiment of the present invention Timing chart showing waveforms and lighting / unlit state of each color of backlight block The block diagram which shows the structure of the liquid crystal display device in the 3rd Embodiment of this invention. The block diagram which shows the detailed structure of the illumination system of the liquid crystal display device in the 3rd Embodiment of this invention. (A) In the third embodiment of the present invention, when the voltage corresponding to black is written to the display element of the pixel, the voltage corresponding to white is written to the display element of the pixel. (B) In the third embodiment of the present invention, when the voltage corresponding to white is written in the display element of the pixel, it corresponds to black. Diagram showing how the voltage written to the pixel display element changes when the voltage is written to the pixel display element (A) The figure which shows an example of the brightness | luminance table in the 3rd Embodiment of this invention (b) The figure which shows an example of the brightness | luminance table in the 3rd Embodiment of this invention (c) The 3rd Embodiment of this invention Showing an example of a luminance table in the form of (A) It is sectional drawing which showed typically the orientation state of the liquid crystal molecule which the display element of OCB mode has, and is sectional drawing which shows a voltage application state (b) The orientation state of the liquid crystal molecule which the display element of OCB mode has typically (C) A cross-sectional view schematically showing an alignment state of liquid crystal molecules included in an OCB mode display element, and showing a state in which no voltage is applied. Figure Block diagram showing the configuration of a conventional liquid crystal display device Timing chart showing voltage waveforms written in the display elements of specific pixels of a conventional liquid crystal display device and the lighting / extinguishing state of each color of the backlight

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1 'Liquid crystal display device 2 Source driver 3 Gate driver 4 Controller 10 Liquid crystal display panel 11 Backlight 13a, 13b, 13c, 13d, 13e LED
14a, 14b, 14c, 14d, 14e LED
15a, 15b, 15c, 15d, 15e Backlight block 16 Input power supply 17 Liquid crystal drive voltage generation circuit 18 Dimming unit 19, 19 'Backlight control unit 21 Signal processing unit 23 Timing control unit 24 D / A conversion unit 25 Shift register 27 Temperature sensor 28 Luminance table selection unit 33 Dimming control unit 40 Reference value storage unit 44 Lighting ratio storage unit 45 Analysis result storage unit 45a Last pixel write voltage arrival time 45b First pixel write voltage arrival time 45c Last pixel black insertion Voltage arrival time 45d Middle pixel write voltage closest approach time 45e Last pixel threshold voltage arrival time 45f First pixel threshold voltage departure time 47a Red LED lighting start time 47b Red LED lighting end time 47c Green LED lighting start time 47d Green LED lighting end time 4 e Blue LED lighting start timing 47f Blue LED lighting end timing 46 Arithmetic unit 47 Timing storage unit 48, 48 'Luminance table storage unit 77a First scanning line 77b Middle scanning line 77c Last scanning line 78a First pixel 78b Middle The last pixel 78c

Claims (13)

A liquid crystal display panel having signal lines and scanning lines formed in a matrix, and liquid crystal display elements formed corresponding to the intersections of the signal lines and the scanning lines;
A source driver that applies an applied voltage corresponding to display data to a signal line of the liquid crystal display panel;
The luminance can be increased or decreased continuously or stepwise, and a backlight for illuminating the liquid crystal display panel;
A backlight control unit that controls the luminance of the backlight based on a write voltage in which the applied voltage is written to the liquid crystal display element via the signal line during a predetermined lighting period of the backlight; A liquid crystal display device comprising: The liquid crystal display panel has a storage capacity for each liquid crystal display element,
The liquid crystal display device according to claim 1, wherein the write voltage is a voltage at which the applied voltage held in the storage capacitor via the signal line is written to the liquid crystal display element. A storage unit that stores in advance backlight luminance information that associates the luminance of the backlight with the writing voltage;
The liquid crystal display device according to claim 1, wherein the backlight control unit controls the luminance of the backlight using the backlight luminance information. A temperature sensor for detecting the temperature of the liquid crystal display panel;
The storage unit stores a plurality of backlight luminance information according to the detected temperature,
The liquid crystal display according to claim 3, wherein the backlight control unit controls the luminance of the backlight using the backlight luminance information corresponding to the detected temperature among the plurality of types of backlight luminance information. apparatus.   The liquid crystal according to claim 1, wherein controlling the luminance of the backlight based on the writing voltage is setting the luminance of the backlight to a luminance according to a ratio of the writing voltage to the applied voltage. Display device.   When the voltage written in the liquid crystal display element reaches the applied voltage, the write voltage is (1) the liquid crystal display element existing on the scanning line scanned at the beginning of one frame period or one field period. 2. The liquid crystal display device according to claim 1, wherein the written voltage is (2) a voltage written in the liquid crystal display element existing on a scanning line scanned at the end of the one frame period or the one field period. .   When the voltage written in the liquid crystal display element does not reach the applied voltage, the write voltage is the write voltage of the liquid crystal display element present on the scanning line located in the center of the liquid crystal display panel. The liquid crystal display device according to claim 1.   The liquid crystal display device according to claim 1, wherein the backlight control unit controls the luminance of the backlight by setting a duty of a PWM signal supplied to the backlight.   The liquid crystal display device according to claim 1, wherein the backlight control unit controls a luminance of the backlight by controlling a voltage supplied to the backlight.   The liquid crystal display device according to claim 1, wherein the backlight control unit controls the luminance of the backlight by controlling a current supplied to the backlight. A liquid crystal display panel having signal lines and scanning lines formed in a matrix, and liquid crystal display elements formed corresponding to the intersections of the signal lines and the scanning lines;
A source driver that applies an applied voltage corresponding to display data to a signal line of the liquid crystal display panel;
A method of driving a liquid crystal display device that drives a liquid crystal display device that can be increased or decreased in luminance continuously or stepwise and includes a backlight that illuminates the liquid crystal display panel,
A method for driving a liquid crystal display device, comprising: a backlight control step for controlling the luminance of the backlight based on a write voltage in which the applied voltage is a voltage written to the liquid crystal display element via the signal line.   12. The backlight for controlling the luminance of the backlight based on a write voltage in which the applied voltage is a voltage written to the liquid crystal display element via the signal line in the driving method of the liquid crystal display device according to claim 11. A program for causing a computer to execute control steps.   A recording medium on which the program according to claim 12 is recorded, wherein the recording medium can be processed by a computer.

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