WO2011148684A1 - Liquid crystal display device - Google Patents

Liquid crystal display device Download PDF

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Publication number
WO2011148684A1
WO2011148684A1 PCT/JP2011/054098 JP2011054098W WO2011148684A1 WO 2011148684 A1 WO2011148684 A1 WO 2011148684A1 JP 2011054098 W JP2011054098 W JP 2011054098W WO 2011148684 A1 WO2011148684 A1 WO 2011148684A1
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WO
WIPO (PCT)
Prior art keywords
liquid crystal
backlight
lighting
crystal panel
temperature
Prior art date
Application number
PCT/JP2011/054098
Other languages
French (fr)
Japanese (ja)
Inventor
暎 冨吉
Original Assignee
シャープ株式会社
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Publication of WO2011148684A1 publication Critical patent/WO2011148684A1/en

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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/001—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes using specific devices not provided for in groups G09G3/02 - G09G3/36, e.g. using an intermediate record carrier such as a film slide; Projection systems; Display of non-alphanumerical information, solely or in combination with alphanumerical information, e.g. digital display on projected diapositive as background
    • G09G3/003—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes using specific devices not provided for in groups G09G3/02 - G09G3/36, e.g. using an intermediate record carrier such as a film slide; Projection systems; Display of non-alphanumerical information, solely or in combination with alphanumerical information, e.g. digital display on projected diapositive as background to produce spatial visual effects
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/3406—Control of illumination source
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2310/00—Command of the display device
    • G09G2310/08—Details of timing specific for flat panels, other than clock recovery
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance
    • G09G2320/0238—Improving the black level
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance
    • G09G2320/0252—Improving the response speed
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/04—Maintaining the quality of display appearance
    • G09G2320/041—Temperature compensation
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/0626—Adjustment of display parameters for control of overall brightness
    • G09G2320/0633—Adjustment of display parameters for control of overall brightness by amplitude modulation of the brightness of the illumination source
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/0626—Adjustment of display parameters for control of overall brightness
    • G09G2320/064—Adjustment of display parameters for control of overall brightness by time modulation of the brightness of the illumination source

Definitions

  • the present invention relates to a liquid crystal display device used for a flat-screen television receiver or the like.
  • liquid crystal display devices capable of displaying stereoscopic images have come out.
  • the right image is observed with the right eye and the left eye image is observed with the left eye, so that the observer combines the respective images in the head and recognizes them as a stereoscopic image.
  • active shutter glasses that block the right-eye field of view or the left-eye field of view in many cases are often used.
  • the liquid crystal panel when the temperature of the liquid crystal is low, the response speed of the liquid crystal panel is lowered and the image display quality of the liquid crystal display device is lowered.
  • the liquid crystal panel in order to improve the response speed of the liquid crystal panel at a low temperature, the liquid crystal panel is heated with heat generated when the backlight is turned on. That is, when the temperature of the liquid crystal panel is low, the backlight is always turned on, and the temperature of the liquid crystal panel is rapidly increased by the heat from the backlight to increase the response speed. This suppresses a decrease in response speed due to the temperature of the liquid crystal panel, and improves the display quality of the image.
  • FIG. 6 is a diagram showing a backlight lighting period and liquid crystal response characteristics of a conventional liquid crystal display device.
  • the horizontal axis represents time
  • the vertical axis represents the light transmittance of the liquid crystal, the luminance of the backlight, and the luminance of the light transmitted through the liquid crystal panel (the luminance of the image displayed on the liquid crystal panel).
  • FIG. 6 illustrates, as a model, the case where the image for the right eye is one white and the image for the left eye is one black for convenience.
  • the response speed is fast.
  • the light transmittance of the liquid crystal panel is instantaneously 100% (for the right eye) when the image display period is switched. Image period) or 0% (left-eye image period).
  • the response speed is slow, and as shown by the solid line in FIG. 6, the light transmittance of the liquid crystal panel changes more slowly than at a high temperature.
  • the liquid crystal panel cannot completely block the light, and the light is transmitted and the luminance is generated.
  • a black-color image should be displayed originally, but a white image with low luminance (in other words, a part of the right-eye image) is displayed, and other than the left-eye image.
  • the image will reach the left eye.
  • Crosstalk occurs by observing an image different from the image that should be originally observed (in many cases, an afterimage of the previous period). In the above example, crosstalk occurs on the left eye side, but such a phenomenon also occurs on the right eye side due to the same cause.
  • an object of the present invention is to provide a liquid crystal display device capable of suppressing the occurrence of crosstalk regardless of the temperature of the liquid crystal panel.
  • the present invention provides a backlight using an LED disposed on the back surface of a liquid crystal display panel as a light source, and supplies a driving current as a pulse current to the backlight to turn on / off the backlight.
  • a liquid crystal display device comprising backlight drive means for controlling driving, comprising panel temperature acquisition means for acquiring the temperature of the liquid crystal display panel, wherein the temperature of the liquid crystal panel is at the time of steady operation of the liquid crystal display device When the temperature of the liquid crystal panel is lower, the lighting duty ratio is determined so that the ON time of the driving current is shorter as the temperature of the liquid crystal panel is lower, and a dimming control signal that includes information on the lighting duty ratio and is sent to the backlight driving means And a dimming signal generating means for generating.
  • the steady operation is when the liquid crystal display device operates for a sufficiently long time and the response speed of the liquid crystal panel is fast.
  • the dimming signal generation means may determine the current value of the driving current based on the lighting duty ratio of the driving current and incorporate it in the dimming control signal.
  • the dimming signal generation means may determine the lighting duty ratio according to which of a plurality of predetermined temperature categories the temperature of the liquid crystal panel belongs to.
  • the dimming signal generating means may determine the lighting duty ratio by a calculation process based on a predetermined calculation formula and the temperature of the liquid crystal panel.
  • the liquid crystal display device includes a data conversion table in which the lighting duty ratio is determined for each temperature of the liquid crystal panel, and the dimming signal generation unit acquires the temperature of the liquid crystal panel. Then, the lighting duty ratio corresponding to the temperature of the liquid crystal panel may be determined with reference to the data conversion table.
  • the dimming signal generating means determines the lighting start timing of the backlight based on the lighting duty ratio after determining the lighting duty ratio of the drive current, and outputs the lighting control signal to the dimming control signal. It may be included.
  • the dimming signal generation means may determine the lighting start timing of the backlight so as to delay the end of lighting of the backlight as the temperature of the liquid crystal panel is lower, and incorporate it in the dimming control signal. Good.
  • the present invention it is possible to provide a liquid crystal display device that can suppress the occurrence of crosstalk regardless of the temperature of the liquid crystal panel by adjusting the timing of lighting the backlight.
  • FIG. 1 is a block diagram of an example of a liquid crystal display device according to the present invention.
  • the liquid crystal display device A is a liquid crystal display device capable of displaying a stereoscopic image.
  • the liquid crystal display device A includes a liquid crystal panel 1, a backlight 2, an image signal input unit 3, an image processing circuit 4, a liquid crystal driving circuit 5, a backlight driving circuit 6, a dimming signal generation circuit 7, A main control circuit 8 and a memory 9 are provided.
  • the liquid crystal panel 1 is filled with liquid crystal between glass substrates arranged in parallel.
  • the glass substrate is provided with a transparent electrode made of ITO (Indium Tin Oxide) or the like.
  • ITO Indium Tin Oxide
  • the liquid crystal panel 1 adjusts the light transmittance of light from a backlight disposed on the back surface, and displays an image on the front surface.
  • the backlight 2 is an illuminating device that is disposed on the back surface of the liquid crystal panel 1 that displays an image and includes a plurality of white LEDs or a plurality of sets of RGB three-color LEDs (hereinafter simply referred to as LEDs) as light sources.
  • the backlight 2 is a direct type, and LEDs are two-dimensionally arranged on the surface facing the liquid crystal panel 1.
  • an edge light type can be adopted as the backlight.
  • the image signal input unit 3 is an interface for inputting an image signal.
  • the image processing circuit 4 generates a frame image signal based on the input image signal, and transmits the frame image signal to the liquid crystal driving circuit 5.
  • the frame image signal is a signal of image luminance (pixel gradation) of each of the three primary colors (R, G, and B) of each pixel constituting one frame image in the moving image. Further, when displaying a moving image, frame image signals are sequentially generated and transmitted to the liquid crystal driving circuit 5 each time.
  • the image processing circuit 4 when displaying a stereoscopic image, the image processing circuit 4 generates a right-eye image observed by the observer's right eye and a left-eye image observed by the left eye based on the input image signal. That is, a right-eye image and a left-eye image are generated for each frame of the input image signal. Then, the image processing circuit 4 newly generates a frame image signal with each of the right-eye image and the left-eye image as one frame image, and transmits the frame image signal to the liquid crystal driving circuit 5. Note that the frame image signal of the right-eye image and the frame image signal of the left-eye image are alternately generated and sequentially transmitted to the liquid crystal driving circuit 5.
  • the liquid crystal driving circuit 5 is a circuit for sequentially displaying on the liquid crystal panel 1 an image for one frame corresponding to the frame image signal based on the frame image signal sequentially transmitted from the image processing circuit 4 at a constant cycle. More specifically, the liquid crystal driving circuit 5 supplies a gradation signal having a voltage corresponding to the pixel gradation included in the frame image signal to the transparent electrode of each pixel provided in the liquid crystal display panel 1. . Thereby, in each pixel of the liquid crystal panel 1, the light transmittance is determined for each pixel, and the light from the backlight 2 is transmitted, whereby an image is displayed on the front surface of the liquid crystal panel 1. Further, when a stereoscopic image is displayed on the liquid crystal panel 1, a right-eye image and a left-eye image are alternately displayed.
  • the backlight drive circuit 6 is a circuit that drives the backlight 2.
  • the backlight drive circuit 6 is a circuit that adjusts the luminance of the LED of the backlight 2 in accordance with the dimming control signal SgL from the dimming signal generation circuit 7.
  • the backlight drive circuit 6 supplies the backlight lighting current Ab to the LEDs in accordance with the dimming control signal SgL from the dimming signal generation circuit 7.
  • the backlight lighting current Ab is a pulse current.
  • the LED as the light source of the backlight 2 repeats ON / OFF at a speed that cannot be recognized by human eyes according to the lighting duty ratio of the pulse current.
  • the backlight drive circuit 6 includes a period adjustment circuit 61 that adjusts the period including the lighting duty ratio of the backlight lighting current Ab, and a current adjustment circuit 62 that changes the current level.
  • the cycle adjusting circuit 61 is a circuit that determines the lighting duty ratio and / or the lighting start time of the backlight lighting current Ab.
  • the current adjustment circuit 62 is a circuit that appropriately changes the current level of the backlight lighting current Ab.
  • the dimming control signal SgL includes at least information on the lighting duty ratio and the current level.
  • the cycle adjusting circuit 61 controls the lighting duty ratio of the backlight lighting current Ab by PWM control.
  • the dimming signal generation circuit 7 is a circuit that transmits the dimming control signal SgL to the backlight driving circuit 6 based on the temperature information of the liquid crystal panel 1 from the main control circuit 8. More specifically, the dimming signal generation circuit 7 calculates the backlight from the information on the duty ratio recorded in the memory 9 (duty ratio determination table described later) and the temperature information of the liquid crystal panel 1 sent from the main control circuit 8. 2 (that is, LED) lighting duty ratio is determined. The dimming signal generation circuit 7 determines the backlight lighting current Ab level based on the control signal from the main control circuit 8. Information on the lighting duty ratio and current level of the backlight lighting current Ab is transmitted to the backlight driving circuit 6 as the dimming control signal SgL.
  • the dimming signal generation circuit 7 is an example of a dimming signal generation unit that determines the lighting duty ratio of the backlight 2 and the like.
  • the main control circuit 8 is a control circuit that comprehensively controls the liquid crystal display device A.
  • the main control circuit 8 includes an arithmetic processing unit such as an MPU.
  • the main control circuit 8 is connected to a temperature sensor Ts attached to the liquid crystal panel 1 and acquires the temperature of the liquid crystal panel 1 based on information sent from the temperature sensor Ts. Further, the main control circuit 8 also controls a power supply circuit (not shown) that supplies power to the image processing circuit 4, the liquid crystal drive circuit 5, the backlight drive circuit 6, and the dimming signal generation circuit 7.
  • the memory 9 is independent of the main control circuit 8, but may be a part of the main control circuit 8. Examples of the memory 9 include a read-only ROM, a readable / writable RAM, and a flash memory. Further, all or a part of the memory 9 may be separated to the outside.
  • FIG. 2 is an example of a duty ratio determination table referred to by the dimming signal generation circuit.
  • the horizontal axis represents the temperature of the liquid crystal panel
  • the vertical axis represents the lighting duty ratio of the backlight lighting current Ab.
  • the main control circuit 8 acquires the temperature of the liquid crystal panel 1 based on information from the temperature sensor Ts. This temperature may be calculated by the MPU based on a calculation formula incorporated in advance in the main control circuit 8 and information from the temperature sensor Ts, and a temperature acquisition table provided in the memory 9. It may be determined based on (not shown). The temperature information of the liquid crystal panel 1 acquired by the main control circuit 8 is sent to the dimming signal generation circuit 7.
  • the dimming signal generation circuit 7 calls the duty ratio determination table Dt stored in the memory 9 and compares the temperature information of the liquid crystal panel 1 sent from the main control circuit 8 against the duty ratio determination table Dt, and the backlight. The lighting duty ratio of the backlight lighting current Ab of 2 is determined.
  • the lighting duty ratio of the backlight lighting current Ab corresponds to the temperature of the liquid crystal panel 1. That is, when the temperature of the liquid crystal panel 1 is higher than T1 in FIG. 3, the lighting duty ratio of the backlight lighting current Ab is constant at Dty1.
  • the temperature T1 is the temperature of the liquid crystal panel 1 when the liquid crystal display device A is in steady operation.
  • the steady operation is when the operation time of the liquid crystal display device A is long and the response speed of the liquid crystal panel 1 is fast enough to suppress crosstalk.
  • the rated duty ratio and the rated current are predetermined for the LED, and the lighting duty ratio Dty1 does not exceed the rated duty ratio.
  • the LED of the backlight is driven with the lighting duty ratio Dty1 regardless of the temperature of the liquid crystal panel.
  • the temperature of the liquid crystal panel 1 when the temperature of the liquid crystal panel 1 is lower than T1 in FIG. 2, the temperature of the liquid crystal panel 1 and the lighting duty ratio have a linear relationship.
  • the temperature of the liquid crystal panel 1 when the temperature of the liquid crystal panel 1 is T2 (T1> T2), the lighting duty ratio of the backlight lighting current Ab is Dty2.
  • the lighting duty ratio is determined from the temperature of the liquid crystal panel 1, such as a step-like one, a function expressed by some function, or a value that determines the previous and next numerical values based on a conversion table and determines a final numerical value by interpolation. What can be used can be widely adopted.
  • FIG. 3 is a diagram showing an example of a backlight lighting period and liquid crystal response characteristics when the liquid crystal display device according to the present invention is cold-started.
  • FIG. 3 shows a model in which the image for the right eye is a white color image and the image for the left eye is a black color image.
  • the liquid crystal display device A is in a state in which the observer wears active shutter glasses that alternately block the field of view of the right eye or the left eye so that the image for the right eye is accurately observed with the right eye and the image for the left eye is observed with the left eye 3D image is displayed.
  • FIG. 3 shows the light transmittance, the luminance of the backlight, and the luminance of the light transmitted through the liquid crystal panel when the image is changed at an arbitrary position on the liquid crystal panel 1.
  • the light transmittance of the liquid crystal panel 1 shown in FIG. 3 is indicated by a solid line when the temperature of the liquid crystal panel 1 is low, that is, when the response speed of the liquid crystal panel 1 is slow.
  • the light transmittance of the liquid crystal panel 1 when the liquid crystal panel 1 and the liquid crystal display device A are heated by driving to be in a steady operation is indicated by a dotted line.
  • the luminance of light transmitted through the liquid crystal display panel in the conventional liquid crystal display device is indicated by a two-dot chain line.
  • a period for displaying an image for the left eye appears after a period for displaying an image for the right eye (an image period for the right eye).
  • the right-eye image period and the left-eye image period have the same length, and here, 1/120 second (when a moving image of 60 frames per second, which is normally used, is displayed stereoscopically) Length).
  • the lengths of both periods are not limited to this, and may be any length that does not cause image flicker.
  • the active shutter glasses block the left eye view during the right eye image period, and block the right eye view during the left eye image period.
  • the temperature of the liquid crystal panel 1 of the liquid crystal display device A is T2 shown in FIG.
  • the lighting duty ratio of the backlight lighting current Ab is Dty2, which is smaller than the lighting duty ratio Dty1 during steady operation. That is, as shown in FIG. 3, the lighting time of the backlight 2 is shorter than that in the steady operation.
  • the backlight drive circuit 6 adjusts the backlight lighting current Ab so that the lighting start timing of the backlight 2 is delayed in order to match the timing of turning off with the steady operation.
  • the current level of the backlight lighting current Ab at this time is Lv1.
  • FIG. 4 is a diagram showing another example of the backlight lighting period and the liquid crystal response characteristics when the liquid crystal display device according to the present invention is cold-started.
  • FIG. 4 is the same as the diagram shown in FIG. 3 except that the lighting start timing of the backlight is different.
  • the liquid crystal panel 1 has a low-speed response speed as shown in FIG. 3, but as time passes, the light transmittance approaches a required value.
  • the required light transmittance here, 0%
  • the required light transmittance approaches the end of the period.
  • the dimming signal generation circuit 7 determines the timing at which the backlight 2 (LED) is switched from the lit state to the unlit state at the point at which the period is switched (in FIG. 4, the point at which the right-eye image period is switched to the left-eye image period, (Or vice versa). In this way, by bringing the lighting end of the backlight 2 close to the switching point of the period, even when the response speed of the liquid crystal panel 1 is slow, the light transmittance of the liquid crystal panel 1 becomes a value required in each frame. When close, the backlight 2 can be turned on. Thereby, the brightness of the image displayed on the liquid crystal panel 1 can be increased, and crosstalk can be reduced. Note that the lighting start of the backlight 2 can be determined based on the lighting duty ratio. In addition, the lighting start of the backlight 2 can be set so as to shift to the end side of each frame when the temperature of the liquid crystal panel 1 is low.
  • FIG. 5 is a diagram showing another example of a backlight lighting period and liquid crystal response characteristics when the liquid crystal display device according to the present invention is cold-started.
  • the lighting duty ratio is lowered and the lighting time of the backlight 2 is shortened in order to suppress the occurrence of crosstalk caused by a decrease in response speed due to the low temperature of the liquid crystal panel 1.
  • the apparent brightness of the image displayed on the liquid crystal panel 1 is lowered.
  • the dimming signal generation circuit 7 sends the dimming control signal SgL sent to the backlight driving circuit 6 including information on the current level of the backlight lighting current Ab.
  • the backlight driving circuit 6 that has received the dimming control signal SgL determines the lighting duty ratio by the cycle adjusting circuit 61 and the current level by the current adjusting circuit 62 based on the dimming control signal SgL, and supplies the lighting level to the backlight 2. To do.
  • the backlight 2 is lit as shown in FIG. That is, as the lighting duty ratio decreases, the luminance decreases as the lighting period becomes shorter. Instead, increasing the current level from Lv1 to Lv2 increases the brightness when the backlight is lit.
  • the decrease in luminance due to the reduction in the lighting duty ratio is compensated by the increase in luminance due to the increase in the current level, and the luminance of the image displayed on the liquid crystal panel 1 can be adjusted.
  • the current level can be set so that the same luminance as that when the lighting duty ratio is large can be obtained. Since the light transmittance in the image period for the left eye in FIG. 5 approaches the requested light transmittance (here, 0%) with time (around the end of the period), the light transmittance of the light transmitted through the liquid crystal panel 1 is increased. The brightness is lower than that without taking countermeasures.
  • the adjustment signal generation circuit 7 reads the table from the memory 9, and determines from the table based on the lighting duty ratio. Further, even if the lighting duty ratio is changed, the current level of the backlight lighting current Ab may be determined by calculation in the adjustment signal generation circuit 7 so that the apparent luminance of the backlight 2 becomes constant.
  • the image processing circuit 4, the liquid crystal driving circuit 5, the backlight driving circuit 6, the image signal correction circuit 7, and the main control circuit 8 described above are provided as independent circuits. Alternatively, two or more circuits may be combined. Further, the image processing circuit 4 and / or the dimming signal generation circuit 7 is stored in the memory 9 as software and is called by the main control circuit 8 as necessary to generate a frame image signal or a dimming control signal SgL. It may be what performs. Moreover, although the case where the temperature sensor Ts is attached to the liquid crystal panel 1 is described, there is no problem as long as the temperature sensor Ts is attached to a place where the temperature of the liquid crystal panel 1 can be analogized, and the place is not limited. .
  • the liquid crystal display device A is described as an example of a liquid crystal display device that displays a stereoscopic image by a frame sequential method using active shutter glasses.
  • the present invention is not limited to this. Absent.
  • the technology of the present invention can be widely applied to liquid crystal display devices that display images in a time-division manner regardless of stereoscopic images or planar images.
  • the present invention can be used as a display device for devices such as a thin television device, a thin display device, and a mobile phone.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Liquid Crystal Display Device Control (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)

Abstract

A liquid crystal display device is provided with a dimming signal generation means (7) which, when the temperature of the liquid crystal panel (1) is lower than that when the liquid crystal panel (1) is being operated steadily, determines the lighting duty ratio so that the lower the temperature of the liquid crystal panel (1), the shorter the time period during which a drive current is turned on, generates a dimming control signal including information relating to the lighting duty ratio, and sends the generated dimming control signal to a backlight drive means (6).

Description

液晶表示装置Liquid crystal display device
　薄型テレビジョン受像機等に用いられる液晶表示装置に関するものである。 The present invention relates to a liquid crystal display device used for a flat-screen television receiver or the like.
　近年、立体画像を表示可能な液晶表示装置が出てきている。立体画像は右側用の画像が右目で、左目用の画像が左目で観察されることで、観察者が頭の中で各画像を合成し立体画像として認識している。右目用の画像を右目に、左目用の画像を左目に正確に入力するため、一定周期で右目の視界又は左目の視界を遮断するアクティブシャッタメガネを用いる場合が多い。 In recent years, liquid crystal display devices capable of displaying stereoscopic images have come out. In the stereoscopic image, the right image is observed with the right eye and the left eye image is observed with the left eye, so that the observer combines the respective images in the head and recognizes them as a stereoscopic image. In order to accurately input the right-eye image to the right eye and the left-eye image to the left eye, active shutter glasses that block the right-eye field of view or the left-eye field of view in many cases are often used.
　一方、前記液晶表示装置に備えられる液晶パネルは、液晶の温度が低いと、前記液晶パネルの応答速度が低下し、液晶表示装置の画像表示品質が低下する。そこで、特開平５－２８９０５８号公報では、低温時の液晶パネルの応答速度を改善するため、前記液晶パネルを前記バックライトの点灯時に発せられる熱で加熱している。すなわち、前記液晶パネルの温度が低いとき、前記バックライトを常時点灯し、前記バックライトからの熱で、前記液晶パネルを急速に昇温し、応答速度を上げている。これにより、前記液晶パネルの温度による応答速度の低下を抑制し、画像の表示品質を高めている。 On the other hand, in the liquid crystal panel provided in the liquid crystal display device, when the temperature of the liquid crystal is low, the response speed of the liquid crystal panel is lowered and the image display quality of the liquid crystal display device is lowered. In Japanese Patent Laid-Open No. 5-289058, in order to improve the response speed of the liquid crystal panel at a low temperature, the liquid crystal panel is heated with heat generated when the backlight is turned on. That is, when the temperature of the liquid crystal panel is low, the backlight is always turned on, and the temperature of the liquid crystal panel is rapidly increased by the heat from the backlight to increase the response speed. This suppresses a decrease in response speed due to the temperature of the liquid crystal panel, and improves the display quality of the image.
特開平５－２８９０５８号公報Japanese Patent Laid-Open No. 5-289058
　図６は従来の液晶表示装置のバックライトの点灯期間と液晶の応答特性を示す図である。図６は横軸に時間を、縦軸に液晶の光透過率、バックライトの輝度及び液晶パネルを透過した光の輝度（液晶パネルで表示される画像の輝度）をあらわしている。なお、説明をしやすくするために、図６では、便宜上、右目用の画像が白一色で、左目用の画像が黒一色である場合をモデルとして説明している。 FIG. 6 is a diagram showing a backlight lighting period and liquid crystal response characteristics of a conventional liquid crystal display device. In FIG. 6, the horizontal axis represents time, and the vertical axis represents the light transmittance of the liquid crystal, the luminance of the backlight, and the luminance of the light transmitted through the liquid crystal panel (the luminance of the image displayed on the liquid crystal panel). For ease of explanation, FIG. 6 illustrates, as a model, the case where the image for the right eye is one white and the image for the left eye is one black for convenience.
　液晶パネルの温度が高いとき、その応答速度は早く、液晶パネルの光透過率は図６の破線で示すように、画像を表示する期間が切り替わると瞬時に、光透過率も１００％（右目用画像期間）又は０％（左目用画像期間）に近づく。しかしながら、液晶パネルの温度が低いとき、その応答速度が遅く、図６の実線で示すように液晶パネルの光透過率は高温時に比べ緩やかに変化する。 When the temperature of the liquid crystal panel is high, the response speed is fast. As shown by the broken line in FIG. 6, the light transmittance of the liquid crystal panel is instantaneously 100% (for the right eye) when the image display period is switched. Image period) or 0% (left-eye image period). However, when the temperature of the liquid crystal panel is low, the response speed is slow, and as shown by the solid line in FIG. 6, the light transmittance of the liquid crystal panel changes more slowly than at a high temperature.
　液晶パネルの応答速度が低いと左目用画像期間内でバックライトが点灯したとき、液晶パネルが完全に光を遮断することができず、光が透過し、輝度が発生する。これにより、本来、左目用画像期間では、黒一色の画像が表示されるべきところ、輝度の低い白色の画像（換言すると、右目用の画像の一部）が表示され、左目用の画像以外の画像が左目に到達することになる。このような、本来観察されるべき画像と異なる画像（前期間の画像の残影の場合が多い）が観察されることで、クロストークが発生する。上記例では左目側でクロストークが発生する場合であるが、このような現象は、同様の原因によって、右目側にも発生する。 If the response speed of the liquid crystal panel is low, when the backlight is turned on during the image period for the left eye, the liquid crystal panel cannot completely block the light, and the light is transmitted and the luminance is generated. As a result, in the left-eye image period, a black-color image should be displayed originally, but a white image with low luminance (in other words, a part of the right-eye image) is displayed, and other than the left-eye image. The image will reach the left eye. Crosstalk occurs by observing an image different from the image that should be originally observed (in many cases, an afterimage of the previous period). In the above example, crosstalk occurs on the left eye side, but such a phenomenon also occurs on the right eye side due to the same cause.
　図６に示すように液晶パネルの応答速度が遅い状態で、特開平５－２８９０５８号公報に示しているようにバックライトを常時点灯させると、右目用画像期間では液晶パネルを透過する光の量が多くなり輝度がアップする。しかしながら、左目用画像期間においても液晶パネルを透過する光の量が多くなり、黒画像を正確に表示できない、すなわち、クロストークがひどくなる問題点がある。前記クロストークは前記液晶パネルが十分な応答速度となる温度に上昇するまで発生する。 As shown in FIG. 6, when the backlight is always lit as shown in Japanese Patent Laid-Open No. 5-28958 when the response speed of the liquid crystal panel is slow, the amount of light transmitted through the liquid crystal panel during the right-eye image period. Increases brightness. However, the amount of light transmitted through the liquid crystal panel increases even in the left-eye image period, and there is a problem that a black image cannot be displayed accurately, that is, crosstalk becomes severe. The crosstalk occurs until the temperature of the liquid crystal panel rises to a sufficient response speed.
　そこで本発明は、液晶パネルの温度に関わらず、クロストークの発生を抑えることができる液晶表示装置を提供することを目的とする。 Therefore, an object of the present invention is to provide a liquid crystal display device capable of suppressing the occurrence of crosstalk regardless of the temperature of the liquid crystal panel.
　上記目的を達成するために本発明は、液晶表示パネルの背面に配置されたＬＥＤを光源とするバックライトと、前記バックライトにパルス電流である駆動電流を供給し、前記バックライトの点灯／消灯駆動を制御するバックライト駆動手段を備えた液晶表示装置であって、前記液晶表示パネルの温度を取得するパネル温度取得手段を備えており、前記液晶パネルの温度が前記液晶表示装置の定常動作時よりも低いとき、前記液晶パネルの温度が低いほど前記駆動電流のＯＮ時間が短くなるように点灯デューティ比を決定し、点灯デューティ比の情報を含み前記バックライト駆動手段に送る調光制御信号を生成する調光信号生成手段とを備えている。 In order to achieve the above object, the present invention provides a backlight using an LED disposed on the back surface of a liquid crystal display panel as a light source, and supplies a driving current as a pulse current to the backlight to turn on / off the backlight. A liquid crystal display device comprising backlight drive means for controlling driving, comprising panel temperature acquisition means for acquiring the temperature of the liquid crystal display panel, wherein the temperature of the liquid crystal panel is at the time of steady operation of the liquid crystal display device When the temperature of the liquid crystal panel is lower, the lighting duty ratio is determined so that the ON time of the driving current is shorter as the temperature of the liquid crystal panel is lower, and a dimming control signal that includes information on the lighting duty ratio and is sent to the backlight driving means And a dimming signal generating means for generating.
　この構成によると、バックライトの点灯時間を短くすることで、バックライトからの光が誤って液晶パネルを透過するのを抑えることができる。これにより、正しくない画像が前記液晶パネルに表示されるクロストークを抑えることができる。なお、ここで、定常動作とは、前記液晶表示装置が十分長く動作しており、前記液晶パネルの応答速度が速いときのことである。 According to this configuration, by shortening the lighting time of the backlight, it is possible to prevent light from the backlight from being erroneously transmitted through the liquid crystal panel. As a result, crosstalk in which an incorrect image is displayed on the liquid crystal panel can be suppressed. Here, the steady operation is when the liquid crystal display device operates for a sufficiently long time and the response speed of the liquid crystal panel is fast.
　上記構成において、前記調光信号生成手段が、前記駆動電流の前記点灯デューティ比を基に前記駆動電流の電流値を決定し、前記調光制御信号に盛り込むようにしてもよい。 In the above configuration, the dimming signal generation means may determine the current value of the driving current based on the lighting duty ratio of the driving current and incorporate it in the dimming control signal.
　上記構成において、前記調光信号生成手段は、前記液晶パネルの温度が予め定められた複数段階の温度の区分のいずれに属するかに応じて、前記点灯デューティ比を決定してもよい。 In the above-described configuration, the dimming signal generation means may determine the lighting duty ratio according to which of a plurality of predetermined temperature categories the temperature of the liquid crystal panel belongs to.
　上記構成において、前記調光信号生成手段は、予め与えられている演算式と前記液晶パネルの温度とを基に、演算処理にて前記点灯デューティ比を決定してもよい。 In the above configuration, the dimming signal generating means may determine the lighting duty ratio by a calculation process based on a predetermined calculation formula and the temperature of the liquid crystal panel.
　上記構成において、前記液晶表示装置は、前記液晶パネルの温度毎に前記点灯デューティ比が決められているデータ変換テーブルを備えており、前記調光信号生成手段は、前記液晶パネルの温度を取得した後、前記データ変換テーブルを参照し、前記液晶パネルの温度に対応した点灯デューティ比を決定してもよい。 In the above configuration, the liquid crystal display device includes a data conversion table in which the lighting duty ratio is determined for each temperature of the liquid crystal panel, and the dimming signal generation unit acquires the temperature of the liquid crystal panel. Then, the lighting duty ratio corresponding to the temperature of the liquid crystal panel may be determined with reference to the data conversion table.
　上記構成において、前記調光信号生成手段は、前記駆動電流の前記点灯デューティ比を決定した後、前記点灯デューティ比を基に、前記バックライトの点灯開始時期を決定し、前記調光制御信号に盛り込んでもよい。 In the above configuration, the dimming signal generating means determines the lighting start timing of the backlight based on the lighting duty ratio after determining the lighting duty ratio of the drive current, and outputs the lighting control signal to the dimming control signal. It may be included.
　上記構成において、前記調光信号生成手段は、前記液晶パネルの温度が低いほど、前記バックライトの点灯終了を遅らせるように前記バックライトの点灯開始時期を決定し、前記調光制御信号に盛り込んでもよい。 In the above-described configuration, the dimming signal generation means may determine the lighting start timing of the backlight so as to delay the end of lighting of the backlight as the temperature of the liquid crystal panel is lower, and incorporate it in the dimming control signal. Good.
　本発明によると、バックライトの点灯のタイミングを調整することで、液晶パネルの温度に関わらず、クロストークの発生を抑えることができる液晶表示装置を提供することができる。 According to the present invention, it is possible to provide a liquid crystal display device that can suppress the occurrence of crosstalk regardless of the temperature of the liquid crystal panel by adjusting the timing of lighting the backlight.
本発明にかかる液晶表示装置のブロック図である。It is a block diagram of the liquid crystal display device concerning this invention. 調光信号生成回路によって参照される点灯デューティ比決定テーブルの一例を示す図である。It is a figure which shows an example of the lighting duty ratio determination table referred by the dimming signal generation circuit. 本発明にかかる液晶表示装置の冷間起動時におけるバックライトの点灯期間と液晶の応答特性の一例を示す図である。It is a figure which shows an example of the lighting period of the backlight at the time of the cold starting of the liquid crystal display device concerning this invention, and the response characteristic of a liquid crystal. 本発明にかかる液晶表示装置の冷間起動時におけるバックライトの点灯期間と液晶の応答特性の他の例を示す図である。It is a figure which shows the other example of the lighting period of the backlight at the time of the cold starting of the liquid crystal display device concerning this invention, and the response characteristic of a liquid crystal. 本発明にかかる液晶表示装置の冷間起動時におけるバックライトの点灯期間と液晶の応答特性の他の例を示す図である。It is a figure which shows the other example of the lighting period of the backlight at the time of the cold starting of the liquid crystal display device concerning this invention, and the response characteristic of a liquid crystal. 従来の液晶表示装置のバックライトの点灯期間と液晶の応答特性を示す図である。It is a figure which shows the lighting period of the backlight of the conventional liquid crystal display device, and the response characteristic of a liquid crystal.
　以下に本発明の実施形態について図面を参照して説明する。図１は本発明にかかる液晶表示装置の一例のブロック図である。図１に示すように、液晶表示装置Ａは、立体画像を表示することが可能な液晶表示装置である。液晶表示装置Ａは、液晶パネル１と、バックライト２と、画像信号入力部３と、画像処理回路４と、液晶駆動回路５と、バックライト駆動回路６と、調光信号生成回路７と、メイン制御回路８と、メモリ９とを備えている。 Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an example of a liquid crystal display device according to the present invention. As shown in FIG. 1, the liquid crystal display device A is a liquid crystal display device capable of displaying a stereoscopic image. The liquid crystal display device A includes a liquid crystal panel 1, a backlight 2, an image signal input unit 3, an image processing circuit 4, a liquid crystal driving circuit 5, a backlight driving circuit 6, a dimming signal generation circuit 7, A main control circuit 8 and a memory 9 are provided.
　液晶パネル１は、平行に配置されたガラス基板の間に液晶が充填されている。ガラス基板にはＩＴＯ（Indium　Tin　Oxide）等で形成された透明電極が備えられており、透明電極を利用して液晶に電圧を印加することで、液晶パネル１に入射される光の光透過率が調整される。液晶パネル１は背面に配置されたバックライトからの光の光透過率を調整し、前面に画像を表示する。 The liquid crystal panel 1 is filled with liquid crystal between glass substrates arranged in parallel. The glass substrate is provided with a transparent electrode made of ITO (Indium Tin Oxide) or the like. By applying a voltage to the liquid crystal using the transparent electrode, the light transmittance of light incident on the liquid crystal panel 1 is provided. Is adjusted. The liquid crystal panel 1 adjusts the light transmittance of light from a backlight disposed on the back surface, and displays an image on the front surface.
　バックライト２は、画像を表示する液晶パネル１の背面に配置され、光源として複数個の白色ＬＥＤ又は複数組のＲＧＢ３色のＬＥＤ（以下、単にＬＥＤと称する）を備えた照明装置である。なお、液晶表示装置Ａでは、バックライト２は直下式であり、液晶パネル１と対向する面にＬＥＤが２次元配列されている。また、バックライトとして、直下式以外にもエッジライト式を採用することも可能である。 The backlight 2 is an illuminating device that is disposed on the back surface of the liquid crystal panel 1 that displays an image and includes a plurality of white LEDs or a plurality of sets of RGB three-color LEDs (hereinafter simply referred to as LEDs) as light sources. In the liquid crystal display device A, the backlight 2 is a direct type, and LEDs are two-dimensionally arranged on the surface facing the liquid crystal panel 1. In addition to the direct type, an edge light type can be adopted as the backlight.
　画像信号入力部３は、画像信号を入力するインターフェースである。画像処理回路４は、入力された画像信号に基づいて、フレーム画像信号を生成し、そのフレーム画像信号を液晶駆動回路５に伝送する。なお、フレーム画像信号は、ここでは、動画における１フレームの画像を構成する各画素の３原色（Ｒ、Ｇ、Ｂ）それぞれの画像輝度（画素階調）の信号である。また、動画を表示する場合、フレーム画像信号は順次生成されそのつど液晶駆動回路５に伝送される。 The image signal input unit 3 is an interface for inputting an image signal. The image processing circuit 4 generates a frame image signal based on the input image signal, and transmits the frame image signal to the liquid crystal driving circuit 5. Here, the frame image signal is a signal of image luminance (pixel gradation) of each of the three primary colors (R, G, and B) of each pixel constituting one frame image in the moving image. Further, when displaying a moving image, frame image signals are sequentially generated and transmitted to the liquid crystal driving circuit 5 each time.
　また、画像処理回路４は、立体画像を表示する場合、入力された画像信号をもとに、観察者の右目に観察される右目用画像と左目に観察される左目用画像を生成する。すなわち、入力された画像信号の１フレームごとに右目用画像及び左目用画像を生成する。そして、画像処理回路４は、右目用画像、左目用画像をそれぞれ１つのフレーム画像として新たにフレーム画像信号を生成し、液晶駆動回路５に伝送する。なお、右目用画像のフレーム画像信号、左目用画像のフレーム画像信号は交互に生成され、順次、液晶駆動回路５に伝送される。 Further, when displaying a stereoscopic image, the image processing circuit 4 generates a right-eye image observed by the observer's right eye and a left-eye image observed by the left eye based on the input image signal. That is, a right-eye image and a left-eye image are generated for each frame of the input image signal. Then, the image processing circuit 4 newly generates a frame image signal with each of the right-eye image and the left-eye image as one frame image, and transmits the frame image signal to the liquid crystal driving circuit 5. Note that the frame image signal of the right-eye image and the frame image signal of the left-eye image are alternately generated and sequentially transmitted to the liquid crystal driving circuit 5.
　液晶駆動回路５は、画像処理回路４から一定周期で順次伝送されてくるフレーム画像信号に基づいて、そのフレーム画像信号に対応する１フレーム分の画像を液晶パネル１に順次表示させる回路である。具体的に説明すると、液晶駆動回路５は、液晶表示パネル１に設けられた各画素の透明電極に対し、フレーム画像信号に含まれる画素階調に応じた電圧の階調信号を供給している。これにより、液晶パネル１の各画素では、画素毎に光の光透過率が決定され、バックライト２からの光が透過することで、液晶パネル１の前面に画像が表示される。さらに、液晶パネル１で立体画像を表示する場合、右目用画像と左目用画像が交互に表示される。 The liquid crystal driving circuit 5 is a circuit for sequentially displaying on the liquid crystal panel 1 an image for one frame corresponding to the frame image signal based on the frame image signal sequentially transmitted from the image processing circuit 4 at a constant cycle. More specifically, the liquid crystal driving circuit 5 supplies a gradation signal having a voltage corresponding to the pixel gradation included in the frame image signal to the transparent electrode of each pixel provided in the liquid crystal display panel 1. . Thereby, in each pixel of the liquid crystal panel 1, the light transmittance is determined for each pixel, and the light from the backlight 2 is transmitted, whereby an image is displayed on the front surface of the liquid crystal panel 1. Further, when a stereoscopic image is displayed on the liquid crystal panel 1, a right-eye image and a left-eye image are alternately displayed.
　バックライト駆動回路６は、バックライト２を駆動する回路である。バックライト駆動回路６は調光信号生成回路７からの調光制御信号ＳｇＬに従って、バックライト２のＬＥＤの輝度を調整する回路である。バックライト駆動回路６は、調光信号生成回路７からの調光制御信号ＳｇＬに従って、バックライト点灯電流ＡｂをＬＥＤに供給する。バックライト点灯電流Ａｂはパルス電流である。バックライト２の光源であるＬＥＤはパルス電流の点灯デューティ比に従って人間の目で認識できない程度の速さでＯＮ／ＯＦＦを繰り返す。 The backlight drive circuit 6 is a circuit that drives the backlight 2. The backlight drive circuit 6 is a circuit that adjusts the luminance of the LED of the backlight 2 in accordance with the dimming control signal SgL from the dimming signal generation circuit 7. The backlight drive circuit 6 supplies the backlight lighting current Ab to the LEDs in accordance with the dimming control signal SgL from the dimming signal generation circuit 7. The backlight lighting current Ab is a pulse current. The LED as the light source of the backlight 2 repeats ON / OFF at a speed that cannot be recognized by human eyes according to the lighting duty ratio of the pulse current.
　バックライト駆動回路６は、バックライト点灯電流Ａｂの点灯デューティ比を含む周期を調整する周期調整回路６１と、電流レベルを変更する電流調整回路６２とを備えている。周期調整回路６１はバックライト点灯電流Ａｂの点灯デューティ比及び（又は）点灯開始時間を決定する回路である。また、電流調整回路６２は、バックライト点灯電流Ａｂの電流レベルを適宜変更する回路である。なお、調光制御信号ＳｇＬには、少なくとも、点灯デューティ比及び電流レベルの情報を含んでいる。なお、周期調整回路６１はＰＷＭ制御でバックライト点灯電流Ａｂの点灯デューティ比を制御している。 The backlight drive circuit 6 includes a period adjustment circuit 61 that adjusts the period including the lighting duty ratio of the backlight lighting current Ab, and a current adjustment circuit 62 that changes the current level. The cycle adjusting circuit 61 is a circuit that determines the lighting duty ratio and / or the lighting start time of the backlight lighting current Ab. The current adjustment circuit 62 is a circuit that appropriately changes the current level of the backlight lighting current Ab. The dimming control signal SgL includes at least information on the lighting duty ratio and the current level. The cycle adjusting circuit 61 controls the lighting duty ratio of the backlight lighting current Ab by PWM control.
　調光信号生成回路７は、メイン制御回路８からの液晶パネル１の温度情報をもとに、バックライト駆動回路６に調光制御信号ＳｇＬを伝送する回路である。さらに詳しく説明すると、調光信号生成回路７はメモリ９に記録されているデューティ比の情報（後述のデューティ比決定テーブル）と、メイン制御回路８から送られる液晶パネル１の温度情報から、バックライト２（すなわち、ＬＥＤ）の点灯デューティ比を決定する。また、調光信号生成回路７はメイン制御回路８からの制御信号を基に、バックライト点灯電流Ａｂレベルを決定する。バックライト点灯電流Ａｂの点灯デューティ比及び電流レベルの情報は調光制御信号ＳｇＬとしてバックライト駆動回路６に伝送される。なお、調光信号生成回路７はバックライト２の点灯デューティ比等を決定する調光信号生成手段の一例である。 The dimming signal generation circuit 7 is a circuit that transmits the dimming control signal SgL to the backlight driving circuit 6 based on the temperature information of the liquid crystal panel 1 from the main control circuit 8. More specifically, the dimming signal generation circuit 7 calculates the backlight from the information on the duty ratio recorded in the memory 9 (duty ratio determination table described later) and the temperature information of the liquid crystal panel 1 sent from the main control circuit 8. 2 (that is, LED) lighting duty ratio is determined. The dimming signal generation circuit 7 determines the backlight lighting current Ab level based on the control signal from the main control circuit 8. Information on the lighting duty ratio and current level of the backlight lighting current Ab is transmitted to the backlight driving circuit 6 as the dimming control signal SgL. The dimming signal generation circuit 7 is an example of a dimming signal generation unit that determines the lighting duty ratio of the backlight 2 and the like.
　メイン制御回路８は液晶表示装置Ａを総合的に制御する制御回路である。メイン制御回路８はＭＰＵ等の演算処理装置を備えている。また、メイン制御回路８は液晶パネル１に取り付けられた温度センサＴｓと接続されており、温度センサＴｓより送られてくる情報を基に液晶パネル１の温度を取得する。さらに、メイン制御回路８は画像処理回路４、液晶駆動回路５、バックライト駆動回路６、調光信号生成回路７に電力を供給する電源回路（不図示）の制御もしている。なお、メモリ９はメイン制御回路８と独立しているが、メイン制御回路８の一部であってもよい。メモリ９として、読み出し専用のＲＯＭ、読み書き可能なＲＡＭ、或いは、フラッシュメモリ等を挙げることができる。また、メモリ９の全部或いは一部を外部に切り離すことができるようになっていてもよい。 The main control circuit 8 is a control circuit that comprehensively controls the liquid crystal display device A. The main control circuit 8 includes an arithmetic processing unit such as an MPU. The main control circuit 8 is connected to a temperature sensor Ts attached to the liquid crystal panel 1 and acquires the temperature of the liquid crystal panel 1 based on information sent from the temperature sensor Ts. Further, the main control circuit 8 also controls a power supply circuit (not shown) that supplies power to the image processing circuit 4, the liquid crystal drive circuit 5, the backlight drive circuit 6, and the dimming signal generation circuit 7. The memory 9 is independent of the main control circuit 8, but may be a part of the main control circuit 8. Examples of the memory 9 include a read-only ROM, a readable / writable RAM, and a flash memory. Further, all or a part of the memory 9 may be separated to the outside.
　次に、バックライト駆動回路及び調光信号生成回路を利用してクロストークを抑制する方法について説明する。図２は調光信号生成回路によって参照されるデューティ比決定テーブルの一例である。図２に示すテーブルは横軸が液晶パネルの温度、縦軸がバックライト点灯電流Ａｂの点灯デューティ比である。 Next, a method for suppressing crosstalk using the backlight drive circuit and the dimming signal generation circuit will be described. FIG. 2 is an example of a duty ratio determination table referred to by the dimming signal generation circuit. In the table shown in FIG. 2, the horizontal axis represents the temperature of the liquid crystal panel, and the vertical axis represents the lighting duty ratio of the backlight lighting current Ab.
　まず、メイン制御回路８は温度センサＴｓからの情報を基に、液晶パネル１の温度を取得する。この温度は、メイン制御回路８に予め組み込まれている計算式と温度センサＴｓからの情報をもとにＭＰＵで算出するものであってもよく、メモリ９に備えられている温度取得用のテーブル（不図示）を基に決定するものであってもよい。メイン制御回路８で取得された液晶パネル１の温度情報は、調光信号生成回路７に送られる。 First, the main control circuit 8 acquires the temperature of the liquid crystal panel 1 based on information from the temperature sensor Ts. This temperature may be calculated by the MPU based on a calculation formula incorporated in advance in the main control circuit 8 and information from the temperature sensor Ts, and a temperature acquisition table provided in the memory 9. It may be determined based on (not shown). The temperature information of the liquid crystal panel 1 acquired by the main control circuit 8 is sent to the dimming signal generation circuit 7.
　調光信号生成回路７はメモリ９に格納されているデューティ比決定テーブルＤｔを呼び出すとともに、メイン制御回路８から送られてきた液晶パネル１の温度情報をデューティ比決定テーブルＤｔに照らし合わせ、バックライト２のバックライト点灯電流Ａｂの点灯デューティ比を決定する。 The dimming signal generation circuit 7 calls the duty ratio determination table Dt stored in the memory 9 and compares the temperature information of the liquid crystal panel 1 sent from the main control circuit 8 against the duty ratio determination table Dt, and the backlight. The lighting duty ratio of the backlight lighting current Ab of 2 is determined.
　図２に示すように、バックライト点灯電流Ａｂの点灯デューティ比は液晶パネル１の温度に対応している。すなわち、液晶パネル１の温度が図３中のＴ１よりも高いとき、バックライト点灯電流Ａｂの点灯デューティ比はＤｔｙ１で一定である。温度Ｔ１は液晶表示装置Ａが定常動作しているときの液晶パネル１の温度である。ここで、定常動作とは、液晶表示装置Ａの動作時間が長く、液晶パネル１の応答速度がクロストークを抑制できる程度に速いときのことである。なお、ＬＥＤには定格デューティ比及び定格電流が予め決められており、点灯デューティ比Ｄｔｙ１は、その定格デューティ比を超えないものである。また、図６に示す従来の液晶表示装置では、バックライトのＬＥＤは液晶パネルの温度に関わらず点灯デューティ比Ｄｔｙ１で駆動されている。 As shown in FIG. 2, the lighting duty ratio of the backlight lighting current Ab corresponds to the temperature of the liquid crystal panel 1. That is, when the temperature of the liquid crystal panel 1 is higher than T1 in FIG. 3, the lighting duty ratio of the backlight lighting current Ab is constant at Dty1. The temperature T1 is the temperature of the liquid crystal panel 1 when the liquid crystal display device A is in steady operation. Here, the steady operation is when the operation time of the liquid crystal display device A is long and the response speed of the liquid crystal panel 1 is fast enough to suppress crosstalk. Note that the rated duty ratio and the rated current are predetermined for the LED, and the lighting duty ratio Dty1 does not exceed the rated duty ratio. In the conventional liquid crystal display device shown in FIG. 6, the LED of the backlight is driven with the lighting duty ratio Dty1 regardless of the temperature of the liquid crystal panel.
　さらに、液晶パネル１の温度が図２中のＴ１よりも低いとき、液晶パネル１の温度と点灯デューティ比とは線形の関係となっている。例えば、液晶パネル１の温度がＴ２（Ｔ１＞Ｔ２）のとき、バックライト点灯電流Ａｂの点灯デューティ比はＤｔｙ２となる。なお、本実施形態では、線形の例を示して説明しているが、線形でなくても良い。例えば、ステップ状のものや、何らかの関数であらわされるもの、或いは変換テーブルを基に前後の数値を決定し補間によって最終的な数値を決定するもの等、液晶パネル１の温度から点灯デューティ比が決定できるものを広く採用することができる。 Furthermore, when the temperature of the liquid crystal panel 1 is lower than T1 in FIG. 2, the temperature of the liquid crystal panel 1 and the lighting duty ratio have a linear relationship. For example, when the temperature of the liquid crystal panel 1 is T2 (T1> T2), the lighting duty ratio of the backlight lighting current Ab is Dty2. In the present embodiment, a linear example is shown and described, but it may not be linear. For example, the lighting duty ratio is determined from the temperature of the liquid crystal panel 1, such as a step-like one, a function expressed by some function, or a value that determines the previous and next numerical values based on a conversion table and determines a final numerical value by interpolation. What can be used can be widely adopted.
　図３は本発明にかかる液晶表示装置の冷間起動時におけるバックライトの点灯期間と液晶の応答特性の一例を示す図である。図３は右目用の画像が白一色の画像で、左目用の画像が黒一色の画像である場合をモデルとしている。また、右目用の画像が右目で、左目用の画像が左目で正確に観察されるように、液晶表示装置Ａは右目又は左目の視界を交互に遮断するアクティブシャッタメガネを観察者が装着した状態で立体画像を表示する。 FIG. 3 is a diagram showing an example of a backlight lighting period and liquid crystal response characteristics when the liquid crystal display device according to the present invention is cold-started. FIG. 3 shows a model in which the image for the right eye is a white color image and the image for the left eye is a black color image. In addition, the liquid crystal display device A is in a state in which the observer wears active shutter glasses that alternately block the field of view of the right eye or the left eye so that the image for the right eye is accurately observed with the right eye and the image for the left eye is observed with the left eye 3D image is displayed.
　図３において、横軸が時間であり、上段より液晶の応答特性、バックライトの輝度及び液晶を透過した光の輝度をあらわしている。なお、図３は液晶パネル１の任意の場所で画像が変化したときの光透過率、バックライトの輝度及び液晶パネルを透過した光の輝度を示している。図３に示す液晶パネル１の光透過率は、液晶パネル１の温度が低いとき、すなわち、液晶パネル１の応答速度が遅いときを実線で示している。また、液晶パネル１及び液晶表示装置Ａが駆動により加熱され、定常動作になったときの液晶パネル１の光透過率は点線で示している。また、図３では従来の液晶表示装置と比較するため、従来の液晶表示装置における液晶表示パネルを透過した光の輝度を二点鎖線で示す。 In FIG. 3, the horizontal axis represents time, and from the top, the response characteristics of the liquid crystal, the luminance of the backlight, and the luminance of the light transmitted through the liquid crystal are shown. FIG. 3 shows the light transmittance, the luminance of the backlight, and the luminance of the light transmitted through the liquid crystal panel when the image is changed at an arbitrary position on the liquid crystal panel 1. The light transmittance of the liquid crystal panel 1 shown in FIG. 3 is indicated by a solid line when the temperature of the liquid crystal panel 1 is low, that is, when the response speed of the liquid crystal panel 1 is slow. Further, the light transmittance of the liquid crystal panel 1 when the liquid crystal panel 1 and the liquid crystal display device A are heated by driving to be in a steady operation is indicated by a dotted line. Further, in FIG. 3, for comparison with a conventional liquid crystal display device, the luminance of light transmitted through the liquid crystal display panel in the conventional liquid crystal display device is indicated by a two-dot chain line.
　図３に示すように、液晶表示装置Ａでは、右目用の画像を表示する期間（右目用画像期間）の後、左目用の画像を表示する期間（左目用画像期間）が現れる。図２に示すように、右目用画像期間及び左目用画像期間は等しい長さであり、ここでは、１／１２０秒（通常よく用いられている１秒間６０フレームの動画を、立体表示したときの長さ）である。両期間の長さは、これに限定されるものではなく、画像のちらつきが発生しない長さであればよい。また、アクティブシャッタメガネは、右目用画像期間に左目の視界を遮断し、左目用画像期間に右目の視界を遮断する。 As shown in FIG. 3, in the liquid crystal display device A, a period for displaying an image for the left eye (a left eye image period) appears after a period for displaying an image for the right eye (an image period for the right eye). As shown in FIG. 2, the right-eye image period and the left-eye image period have the same length, and here, 1/120 second (when a moving image of 60 frames per second, which is normally used, is displayed stereoscopically) Length). The lengths of both periods are not limited to this, and may be any length that does not cause image flicker. Further, the active shutter glasses block the left eye view during the right eye image period, and block the right eye view during the left eye image period.
　冷間起動時において、液晶表示装置Ａの液晶パネル１の温度は図２に示すＴ２となっている。このとき、バックライト点灯電流Ａｂの点灯デューティ比はＤｔｙ２であり、定常動作時の点灯デューティ比Ｄｔｙ１よりも小さい。すなわち、図３に示すように、バックライト２の点灯時間が定常動作時に比べて短くなっている。なお、定常動作時と消灯のタイミングを合わせるため、バックライト駆動回路６はバックライト２に点灯開始時期が遅くなるようにバックライト点灯電流Ａｂを調整する。なお、このときのバックライト点灯電流Ａｂの電流レベルはＬｖ１である。 At the cold start, the temperature of the liquid crystal panel 1 of the liquid crystal display device A is T2 shown in FIG. At this time, the lighting duty ratio of the backlight lighting current Ab is Dty2, which is smaller than the lighting duty ratio Dty1 during steady operation. That is, as shown in FIG. 3, the lighting time of the backlight 2 is shorter than that in the steady operation. Note that the backlight drive circuit 6 adjusts the backlight lighting current Ab so that the lighting start timing of the backlight 2 is delayed in order to match the timing of turning off with the steady operation. Note that the current level of the backlight lighting current Ab at this time is Lv1.
　このとき、図３に示しているように、液晶パネル１の応答速度が遅い場合であっても、バックライト２の点灯時間が短くなっているので、左目画像期間における液晶パネル１を透過する光量の総和（輝度）が少なくなっている。これによって、左目画像期間に表示される左目用の画像の見かけ上の輝度を低下することができ、クロストークが抑制される。 At this time, as shown in FIG. 3, even when the response speed of the liquid crystal panel 1 is slow, the lighting time of the backlight 2 is shortened, so the amount of light transmitted through the liquid crystal panel 1 in the left-eye image period The sum (brightness) of is less. As a result, the apparent luminance of the left-eye image displayed during the left-eye image period can be reduced, and crosstalk is suppressed.
　本発明にかかる液晶表示装置における点灯デューティ比の制御の他の例について図面を参照して説明する。図４は本発明にかかる液晶表示装置の冷間起動時におけるバックライトの点灯期間と液晶の応答特性の他の例を示す図である。図４はバックライトの点灯開始のタイミングが異なる以外は図３に示す図と同じである。液晶パネル１は低温時応答速度が遅くなることは、図３に示しているとおりであるが、時間が経過するに従って、光透過率は要求される値に近づいている。例えば、図４の左目用画像期間では、時間がたつと（期間の終わりごろには）要求された光透過率（ここでは０％）に近づく。また、右目用画像期間においても、期間の終わりごろに要求された光透過率に近づく。 Another example of controlling the lighting duty ratio in the liquid crystal display device according to the present invention will be described with reference to the drawings. FIG. 4 is a diagram showing another example of the backlight lighting period and the liquid crystal response characteristics when the liquid crystal display device according to the present invention is cold-started. FIG. 4 is the same as the diagram shown in FIG. 3 except that the lighting start timing of the backlight is different. As shown in FIG. 3, the liquid crystal panel 1 has a low-speed response speed as shown in FIG. 3, but as time passes, the light transmittance approaches a required value. For example, in the image period for the left eye in FIG. 4, the required light transmittance (here, 0%) approaches as time passes (by the end of the period). Also, in the right eye image period, the required light transmittance approaches the end of the period.
　そこで、調光信号生成回路７は、バックライト２（ＬＥＤ）が点灯状態から消灯状態に切り替わるタイミングを、期間の切り替わる点（図４においては、右目用画像期間から左目用画像期間に切り替わる点、或いはその逆の点）に近づける。このように、バックライト２の点灯終了を期間の切り替わり点に近づけることで、液晶パネル１の応答速度が遅い場合であっても、液晶パネル１の光透過率が各フレームで要求される値に近いとき、バックライト２を点灯させることができる。これにより、液晶パネル１に表示される画像の輝度を高めることができるとともに、クロストークを低減することができる。なお、バックライト２の点灯開始は、点灯デューティ比をもとに決定することが可能である。また、バックライト２の点灯開始を液晶パネル１の温度が低いとき、各フレームの終わり側にずれるように設定するものを挙げることができる。 Therefore, the dimming signal generation circuit 7 determines the timing at which the backlight 2 (LED) is switched from the lit state to the unlit state at the point at which the period is switched (in FIG. 4, the point at which the right-eye image period is switched to the left-eye image period, (Or vice versa). In this way, by bringing the lighting end of the backlight 2 close to the switching point of the period, even when the response speed of the liquid crystal panel 1 is slow, the light transmittance of the liquid crystal panel 1 becomes a value required in each frame. When close, the backlight 2 can be turned on. Thereby, the brightness of the image displayed on the liquid crystal panel 1 can be increased, and crosstalk can be reduced. Note that the lighting start of the backlight 2 can be determined based on the lighting duty ratio. In addition, the lighting start of the backlight 2 can be set so as to shift to the end side of each frame when the temperature of the liquid crystal panel 1 is low.
　本発明にかかる液晶表示装置における点灯デューティ比の制御のさらに他の例について図面を参照して説明する。図５は本発明にかかる液晶表示装置の冷間起動時におけるバックライトの点灯期間と液晶の応答特性の他の例を示す図である。液晶表示装置Ａにおいて、液晶パネル１の低温による応答速度の低下で発生するクロストークの発生を抑えるために、点灯デューティ比を下げバックライト２の点灯時間を短くしている。これにより、液晶パネル１で表示される画像の見かけ上の輝度が低下する。 Still another example of the control of the lighting duty ratio in the liquid crystal display device according to the present invention will be described with reference to the drawings. FIG. 5 is a diagram showing another example of a backlight lighting period and liquid crystal response characteristics when the liquid crystal display device according to the present invention is cold-started. In the liquid crystal display device A, the lighting duty ratio is lowered and the lighting time of the backlight 2 is shortened in order to suppress the occurrence of crosstalk caused by a decrease in response speed due to the low temperature of the liquid crystal panel 1. Thereby, the apparent brightness of the image displayed on the liquid crystal panel 1 is lowered.
　この輝度低下を補うために、調光信号生成回路７は、バックライト駆動回路６に送る調光制御信号ＳｇＬのなかに、バックライト点灯電流Ａｂの電流レベルの情報を含めて送っている。調光制御信号ＳｇＬを受信したバックライト駆動回路６は、調光制御信号ＳｇＬをもとに周期調整回路６１で点灯デューティ比を、電流調整回路６２で電流レベルを決定し、バックライト２に供給する。 In order to compensate for this decrease in luminance, the dimming signal generation circuit 7 sends the dimming control signal SgL sent to the backlight driving circuit 6 including information on the current level of the backlight lighting current Ab. The backlight driving circuit 6 that has received the dimming control signal SgL determines the lighting duty ratio by the cycle adjusting circuit 61 and the current level by the current adjusting circuit 62 based on the dimming control signal SgL, and supplies the lighting level to the backlight 2. To do.
　バックライト２は図５に示すように点灯する。すなわち、点灯デューティ比が小さくなることで、点灯期間は短くなっている分、輝度としては低下する。その代わり、電流レベルをＬｖ１からＬｖ２に上げてやることによって、バックライト点灯時の輝度は上がっている。点灯デューティ比を小さくすることによる輝度低下分を電流レベルを上げてやることによる輝度アップで補っており、液晶パネル１で表示される画像の輝度を調整することができる。例えば、点灯デューティ比が大きい場合と同等の輝度を得ることができるように電流レベルを設定することも可能である。図５中の左目用画像期間での光透過率は時間がたつと（期間の終わりごろには）要求された光透過率（ここでは０％）に近づくため、液晶パネル１を透過した光の輝度は、対策を行わないものよりも低下する。 The backlight 2 is lit as shown in FIG. That is, as the lighting duty ratio decreases, the luminance decreases as the lighting period becomes shorter. Instead, increasing the current level from Lv1 to Lv2 increases the brightness when the backlight is lit. The decrease in luminance due to the reduction in the lighting duty ratio is compensated by the increase in luminance due to the increase in the current level, and the luminance of the image displayed on the liquid crystal panel 1 can be adjusted. For example, the current level can be set so that the same luminance as that when the lighting duty ratio is large can be obtained. Since the light transmittance in the image period for the left eye in FIG. 5 approaches the requested light transmittance (here, 0%) with time (around the end of the period), the light transmittance of the light transmitted through the liquid crystal panel 1 is increased. The brightness is lower than that without taking countermeasures.
　図５に示すように、バックライト２に供給するバックライト点灯電流Ａｂの電流レベルを上げることで、液晶パネル１で表示される画像の輝度を確保しつつ、クロストークの発生を抑制することが可能である。この電流レベルＬｖ２については、メモリ９にテーブルを備えておき、調整信号生成回路７がメモリ９よりテーブルを読み出し、点灯デューティ比をもとにテーブルから決定するものを挙げることができる。また、点灯デューティ比を変更しても、バックライト２の見かけ上の輝度が一定となるように、調整信号生成回路７で演算によりバックライト点灯電流Ａｂの電流レベルを決定してもよい。 As shown in FIG. 5, by increasing the current level of the backlight lighting current Ab supplied to the backlight 2, it is possible to suppress the occurrence of crosstalk while ensuring the luminance of the image displayed on the liquid crystal panel 1. Is possible. As for the current level Lv2, a table is provided in the memory 9, and the adjustment signal generation circuit 7 reads the table from the memory 9, and determines from the table based on the lighting duty ratio. Further, even if the lighting duty ratio is changed, the current level of the backlight lighting current Ab may be determined by calculation in the adjustment signal generation circuit 7 so that the apparent luminance of the backlight 2 becomes constant.
　なお、以上に示した画像処理回路４と、液晶駆動回路５と、バックライト駆動回路６と、画像信号補正回路７と、メイン制御回路８の各回路は、それぞれ独立した回路として備えられていてもよく、２以上の回路がまとめられていてもよい。さらに、画像処理回路４及び（又は）調光信号生成回路７はソフトウェアとしてメモリ９に格納され、必要に応じてメイン制御回路８で呼び出され、フレーム画像信号の生成或いは調光制御信号ＳｇＬの生成を行うものであってもよい。また、温度センサＴｓを液晶パネル１に取り付けた場合について説明しているが、温度センサＴｓは液晶パネル１の温度が類推できる場所に取り付けられておれば問題なく、場所が限定されるものではない。 The image processing circuit 4, the liquid crystal driving circuit 5, the backlight driving circuit 6, the image signal correction circuit 7, and the main control circuit 8 described above are provided as independent circuits. Alternatively, two or more circuits may be combined. Further, the image processing circuit 4 and / or the dimming signal generation circuit 7 is stored in the memory 9 as software and is called by the main control circuit 8 as necessary to generate a frame image signal or a dimming control signal SgL. It may be what performs. Moreover, although the case where the temperature sensor Ts is attached to the liquid crystal panel 1 is described, there is no problem as long as the temperature sensor Ts is attached to a place where the temperature of the liquid crystal panel 1 can be analogized, and the place is not limited. .
　なお、以上に示す各実施形態において、液晶表示装置Ａとして、アクティブシャッタメガネを用いたフレームシーケンシャル方式で立体画像を表示する液晶表示装置を例に説明しているが、これに限定されるものではない。すなわち、本発明の技術は立体画像、平面画像に関係なく、時分割で画像を表示する液晶表示装置に広く適用することが可能である。 In each of the embodiments described above, the liquid crystal display device A is described as an example of a liquid crystal display device that displays a stereoscopic image by a frame sequential method using active shutter glasses. However, the present invention is not limited to this. Absent. In other words, the technology of the present invention can be widely applied to liquid crystal display devices that display images in a time-division manner regardless of stereoscopic images or planar images.
　また、液晶パネル１が低温である場合として、液晶表示装置Ａへの電源投入直後（冷間始動時）を挙げているがこれに限定されるものではない。 In addition, as a case where the liquid crystal panel 1 is at a low temperature, a case immediately after turning on the power to the liquid crystal display device A (during cold start) is mentioned, but it is not limited to this.
　本発明は、薄型テレビジョン装置、薄型ディスプレイ装置、携帯電話等の機器の表示装置として利用することができる。 The present invention can be used as a display device for devices such as a thin television device, a thin display device, and a mobile phone.
１　液晶パネル
２　バックライト
３　画像信号入力部
４　画像処理回路
５　液晶駆動回路
６　バックライト駆動回路
７　調光信号生成回路
８　メイン制御回路
９　メモリ DESCRIPTION OF SYMBOLS 1 Liquid crystal panel 2 Backlight 3 Image signal input part 4 Image processing circuit 5 Liquid crystal drive circuit 6 Backlight drive circuit 7 Dimming signal generation circuit 8 Main control circuit 9 Memory

Claims (7)

  1. 　液晶表示パネルの背面に配置されたＬＥＤを光源とするバックライトと、
    　前記バックライトにパルス電流である駆動電流を供給し、前記バックライトの点灯／消灯駆動を制御するバックライト駆動手段を備えた液晶表示装置であって、
    　前記液晶表示パネルの温度を取得するパネル温度取得手段と、
    　前記液晶パネルの温度が前記液晶表示装置の定常動作時よりも低いとき、前記液晶パネルの温度が低いほど前記駆動電流のＯＮ時間が短くなるように点灯デューティ比を決定し、点灯デューティ比の情報を含む調光制御信号を生成するとともに前記バックライト駆動手段に送る調光信号生成手段とを備えていることを特徴とする液晶表示装置。     A backlight that uses an LED disposed on the back of the liquid crystal display panel as a light source;
    A liquid crystal display device comprising a backlight driving means for supplying a driving current, which is a pulse current, to the backlight, and controlling lighting / extinguishing driving of the backlight;
    Panel temperature acquisition means for acquiring the temperature of the liquid crystal display panel;
    When the temperature of the liquid crystal panel is lower than that during the steady operation of the liquid crystal display device, the lighting duty ratio is determined so that the ON time of the drive current becomes shorter as the temperature of the liquid crystal panel is lower, and information on the lighting duty ratio And a dimming signal generating means for generating a dimming control signal including the dimming control signal and sending the dimming control signal to the backlight driving means.
  2. 　前記調光信号生成手段が、前記駆動電流の前記点灯デューティ比を基に前記駆動電流の電流値を決定し、前記駆動電流の電流値を含む前記調光制御信号を生成する請求項１に記載の液晶表示装置。 The dimming signal generation unit determines a current value of the drive current based on the lighting duty ratio of the drive current, and generates the dimming control signal including the current value of the drive current. Liquid crystal display device.
  3. 　前記調光信号生成手段は、前記液晶パネルの温度が予め定められた複数段階の温度の区分のいずれに属するかに応じて、前記点灯デューティ比を決定する請求項１又は請求項２に記載の液晶表示装置。 3. The lighting duty ratio according to claim 1, wherein the dimming signal generation unit determines the lighting duty ratio according to which of a plurality of predetermined temperature categories the temperature of the liquid crystal panel belongs to. Liquid crystal display device.
  4. 　前記調光信号生成手段は、予め与えられている演算式と前記液晶パネルの温度とを基に、演算処理にて前記点灯デューティ比を決定する請求項１又は請求項２に記載の液晶表示装置。 3. The liquid crystal display device according to claim 1, wherein the dimming signal generation unit determines the lighting duty ratio by a calculation process based on an arithmetic expression given in advance and a temperature of the liquid crystal panel. .
  5. 　前記液晶表示装置は、前記液晶パネルの温度毎に前記点灯デューティ比が決められているデータ変換テーブルを備えており、
    　前記調光信号生成手段は、前記液晶パネルの温度を取得した後、前記データ変換テーブルを参照し、前記液晶パネルの温度に対応した点灯デューティ比を決定する請求項１又は請求項２に記載の液晶表示装置。     The liquid crystal display device includes a data conversion table in which the lighting duty ratio is determined for each temperature of the liquid crystal panel,
    The said light control signal production | generation means determines the lighting duty ratio corresponding to the temperature of the said liquid crystal panel with reference to the said data conversion table, after acquiring the temperature of the said liquid crystal panel. Liquid crystal display device.
  6. 　前記調光信号生成手段が、前記駆動電流の前記点灯デューティ比を決定した後、前記点灯デューティ比を基に、前記バックライトの点灯開始時期を決定し、前記バックライトの点灯開始時期の情報を含む前記調光制御信号を生成する請求項１から請求項５のいずれかに記載の液晶表示装置。 After the dimming signal generating means determines the lighting duty ratio of the drive current, the lighting control timing is determined based on the lighting duty ratio, and information on the backlight lighting start time is obtained. The liquid crystal display device according to claim 1, wherein the dimming control signal is generated.
  7. 　前記調光信号生成手段は、前記液晶パネルの温度が低いほど、前記バックライトの点灯終了を遅らせるように前記バックライトの点灯開始時期を決定し、前記バックライトの点灯開始時期の情報を含む前記調光制御信号を生成する請求項１から請求項６のいずれかに記載の液晶表示装置。 The dimming signal generating means determines the lighting start timing of the backlight so as to delay the end of lighting of the backlight as the temperature of the liquid crystal panel is lower, and includes information on the lighting start timing of the backlight. The liquid crystal display device according to claim 1, which generates a dimming control signal.
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