JP2006330400A - Transmission-type liquid crystal color display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the efficiency of the light emitted from the back light unit and save power, in a liquid crystal color display of a backlight system. <P>SOLUTION: The whole image aura is obtained as the light amount variations in a transmissive liquid crystal color display, except for the details of the image with the backlight system 140, by using the control signal generator 240 to obtain the whole image representing values except the details of the color image to display based on the inputted color image signals, and deciding the coefficients according to the obtained values, then controlling the light amounts of the light-emitting diodes 21R, 21G, 21B in the backlight unit. Furthermore, the light amount difference between the details of the color image and the backlight is displayed on the liquid crystal color display panel 110 by driving it by using the rate changed image signals obtained, by multiplying the inputted color image signals by the reverse numbers of the coefficients to controls the light amount of each color in the backlight unit 140. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a transmissive color liquid crystal display device that displays a color image by illuminating a transmissive color liquid crystal display panel from the back side with a backlight device, and a driving method thereof.

  Instead of CRT (Cathode Ray Tube), which has been used for many years since the start of television broadcasting, it has been made very thin, such as a liquid crystal display (LCD) and a plasma display (PDP). Television receivers have been devised and put into practical use. In particular, liquid crystal display devices using a liquid crystal display panel can be driven with low power consumption, and it is considered that the liquid crystal display device will be used at an accelerated pace due to the price reduction of large liquid crystal display panels. It is a display device that can be expected to develop further.

  The color liquid crystal display device is mainly a backlight system in which a color image is displayed by illuminating a transmissive color liquid crystal display panel including a color filter from the back side with a backlight device. As a light source of a backlight device, a fluorescent lamp such as a CCFL (Cold Cathode Fluorescent Lamp) that emits white light using a fluorescent tube is often used.

  In addition, since the CCFL encloses mercury in a fluorescent tube and thus has an adverse effect on the environment, a light emitting diode (LED) is promising as a light source of a backlight device that replaces the CCFL (for example, Patent Document 1).

  With the development of blue light-emitting diodes, light-emitting diodes that emit red, green, and blue light, which are the three primary colors of light, have been prepared, and red light, green light, and blue light emitted from these light-emitting diodes have been prepared. By mixing colors, white light with high color purity can be obtained. Therefore, by using this light emitting diode as the light source of the backlight device, the color purity of the color light via the liquid crystal display panel is increased, so that the color reproduction range can be greatly expanded compared with the CCFL.

  As a light-emitting diode used as a light source of a backlight device, a light-emitting diode using a high-power light-emitting diode (LED) chip is effective. By using this light-emitting diode, the luminance of the backlight device is greatly improved. Can do.

Japanese Patent Laid-Open No. 7-191311

  By the way, in a backlight type color liquid crystal display device, in a color liquid crystal display panel in which a specified white light is emitted from the back side by the backlight device, only light of a target color component is obtained for each pixel by shielding the white light. Are extracted through a color filter to display a color image.

  That is, as the white light emitted from the backlight device, only the light of the target color component extracted through the color liquid crystal display panel is used. For example, when the entire screen is displayed in red, white light is shielded in the color liquid crystal display panel in pixels other than the pixel provided with the red filter, that is, the pixel provided with the green filter and the blue filter, and the red filter Light of pixels other than the provided pixels is not used.

  As described above, conventionally, in the backlight type color liquid crystal display device, white light including color components that are not used is emitted by the backlight device, and accordingly, power is consumed wastefully.

  Accordingly, an object of the present invention is to increase the utilization efficiency of light emitted from a backlight device and reduce power consumption in a backlight type color liquid crystal display device in view of the conventional problems as described above. is there.

  Other objects of the present invention and specific advantages obtained by the present invention will become more apparent from the description of embodiments described below.

  A transmissive color liquid crystal display device according to the present invention includes a transmissive color liquid crystal display panel and a plurality of light emitting diodes that emit at least red light, green light, and blue light, respectively. Based on the backlight device to illuminate and the input color video signal, the representative value of the entire image excluding the detail portion of the color image to be displayed is obtained, and the light emission amount of each color of the backlight device is determined according to the value. A control signal that generates a light emission amount control signal that determines a coefficient to be controlled, and that generates a ratio-converted video signal by multiplying the input color video signal by a reciprocal of the coefficient that controls the light emission amount of each color of the backlight device. And a display panel driving control for driving the color liquid crystal display panel according to the ratio-converted video signal generated by the control signal generating unit. And a backlight drive control unit that drives the backlight device in accordance with the light emission amount control signal generated by the control signal generation unit, and removes a detail portion of a color image to be displayed by the backlight device. The atmosphere of the entire image is expressed as a change in the amount of light, and the color liquid crystal display panel displays the light amount difference between the detail portion of the color image and the backlight.

  In addition, the present invention provides a transmissive type that displays a color image by a transmissive color liquid crystal display panel illuminated from the back side by a backlight device composed of a plurality of light emitting diodes that emit at least red light, green light, and blue light, respectively. A method for driving a color liquid crystal display device, wherein a representative value of an entire image excluding a detail portion of a color image to be displayed is obtained based on an input color video signal, and a coefficient is determined according to the value to determine a coefficient By controlling the light emission amount of each color of the backlight device, the backlight device expresses the atmosphere of the entire image excluding the detail portion of the color image to be displayed as a light amount change, and the light emission of each color of the backlight device. The color liquid crystal display is obtained by the ratio-converted video signal obtained by multiplying the input color video signal by the inverse of the coefficient for controlling the amount. Panel by driving the, in the color liquid crystal display panel, it is characterized in that so as to display the light intensity difference of the detail portion and the backlight of the color image.

  According to the present invention, based on the input color video signal, the representative value of the entire image excluding the detail portion of the color image to be displayed is obtained, the coefficient is determined according to the value, and each color of the backlight device is determined. By controlling the amount of light emission, the backlight device expresses the atmosphere of the entire image excluding the detail portion of the color image to be displayed as a change in the amount of light, and a coefficient for controlling the light emission amount of each color of the backlight device. The color liquid crystal display panel is driven by a ratio-converted video signal obtained by multiplying the input color video signal by the inverse number, and the color liquid crystal display panel displays a light amount difference between the detail portion of the color image and the backlight. To improve the efficiency of using the light emitted from the backlight device and reduce the power consumption of the transmissive color liquid crystal display device It can be.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Needless to say, the present invention is not limited to the following examples, and can be arbitrarily changed without departing from the gist of the present invention.

  The present invention is applied to, for example, a transmissive color liquid crystal display device 100 configured as shown in FIG.

  The transmissive color liquid crystal display device 100 includes a transmissive color liquid crystal display panel 110 and a backlight device 140 provided on the back side of the color liquid crystal display panel 110. Although not shown, the transmissive color liquid crystal display device 100 includes a receiving unit such as an analog tuner and a digital tuner that receives terrestrial and satellite waves, and a video that processes a video signal and an audio signal received by the receiving unit, respectively. An audio signal output unit such as a speaker that outputs an audio signal processed by the signal processing unit, the audio signal processing unit, and the audio signal processing unit may be provided.

  In the transmissive color liquid crystal display panel 110, two transparent substrates (TFT substrate 111 and counter electrode substrate 112) made of glass or the like are arranged to face each other, and, for example, twisted nematic (TN) liquid crystal is provided in the gap. And a TFT substrate 111 and a counter electrode substrate 112 are sandwiched between two polarizing plates 131 and 132. On the TFT substrate 111, signal lines 114 arranged in a matrix, scanning lines 115, thin film transistors 116 serving as switching elements arranged at intersections of the signal lines 114 and the scanning lines 115, and pixel electrodes 117 are formed. Has been. The thin film transistor 116 is sequentially selected by the scanning line 115 and writes the video signal supplied from the signal line 114 to the corresponding pixel electrode 117. On the other hand, a counter electrode 118 and a color filter 119 are formed on the inner surface of the counter electrode substrate 112.

  The color filter 119 is divided into a plurality of segments corresponding to each pixel. For example, as shown in FIG. 2, it is divided into three segments of a red filter CFR, a green filter CFG, and a blue filter CFB which are three primary colors. The arrangement pattern of the color filter 119 includes a delta arrangement and a square arrangement, although not shown, in addition to the stripe arrangement shown in FIG.

  The transmissive color liquid crystal display device 100 is driven by the active matrix system in such a manner that the transmissive color liquid crystal display panel 110 having such a configuration is irradiated with white light from the back side by the backlight device 140. A desired full-color image can be displayed.

  The backlight device 140 in the liquid crystal display device 100 is an area light type backlight device using a large number of light emitting diodes, and as shown in FIG. In the backlight casing 120 in which the diode is disposed, a diffusion plate 141, a diffusion sheet 142 disposed on the diffusion plate 141, a prism sheet 143, an optical sheet group 145 such as a polarization conversion sheet 144, and the like are provided. It becomes the composition. The diffusing plate 141 makes the luminance emitted from the surface emission uniform by internally diffusing the light emitted from the light source. The optical sheet group 145 functions to increase the luminance in surface emission by raising the illumination light emitted from the diffusion plate 141 in the normal direction of the diffusion plate 141.

FIG. 3 shows a schematic configuration diagram in the backlight housing 120. The backlight housing 120 includes at least a red (R) light emitting diode 21R that emits red (R) light, a green (G) light emitting diode 21G that emits green light, and a blue (B) light emitting that emits blue light. A plurality of light emitting diode units 21 _n (n is a natural number, respectively) including the diode 21B as a light source are provided. The light emitting diode units 21 _n have a longitudinal direction parallel to the horizontal direction of the backlight housing 120 and are arranged in a plurality of rows in the vertical direction in the backlight housing 120.

  The color liquid crystal display device 100 having such a configuration is driven by, for example, a drive circuit 200 as shown in FIG.

  The driving circuit 200 includes a power supply unit 210 that supplies driving power to the color liquid crystal display panel 110 and the backlight device 140, a video signal supplied from the outside, and an image received by a receiving unit (not shown) included in the color liquid crystal display device 100. A video decoder 230 to which a signal is supplied via the input terminal 220, a control signal generator 240 connected to the video decoder 230, a backlight drive controller 250 and a video encoder 260 connected to the control signal generator 240. , And an X driver circuit 270 and a Y driver circuit 280 for driving the color liquid crystal display panel 110 according to the output of the video encoder 260.

  In this drive circuit 200, the video signal input via the input terminal 220 is subjected to signal processing such as chroma processing by the video decoder 230, and further m from the composite signal suitable for driving the color liquid crystal display panel 110. It is converted into RGB data of bits (m is assumed to be 8 to 12), and is supplied to the control signal generator 240 together with the horizontal synchronizing signal H and the vertical synchronizing signal V.

  The control signal creation unit 240 is configured by an FPGA, creates video signal data converted into an RGB ratio that saves power based on the RGB data supplied from the video decoder 230, and generates a horizontal synchronization signal. PWM supplied to the video encoder 260 together with H and the vertical synchronizing signal V, and PWM for controlling the drive current to be passed through the red light emitting diode 21R, the green light emitting diode 21G, and the blue light emitting diode 21B of the backlight device 140 by the backlight drive control unit 250. A control signal is generated and supplied to the backlight drive control unit 250.

  Note that the control signal creation unit 240 can also turn off the red light emitting diode 21R, the green light emitting diode 21G, and the blue light emitting diode 21B of the backlight device 140 in accordance with the video rewriting timing of the color liquid crystal display panel 110, or perform RGB ratio data conversion. The PWM value control is performed simultaneously.

  Here, calculation of the RGB ratio will be described.

  Considering a certain point on the entire screen, a conventional backlight device using CCFL as a backlight light source illuminates with white light in principle, so in the conventional concept, for example, the transmittance of a color liquid crystal display panel is set to R = When an image is displayed with 20%, G = 60%, and B = 80%, the backlight is R = G = B = 100%. However, in this color liquid crystal display device 100, the RGB three-color mixed backlight is used. Using the device 140, the color liquid crystal display panel 110 side is fully opened, that is, the transmittance is R = G = B = 100%), and the red light emitting diode 21R, the green light emitting diode 21G, and the blue light emitting diode 21B of the backlight device 140 are left. By setting the ratio of the amount of emitted light to R = 20%, G = 60%, and B = 80%, the same result can be obtained and power can be saved. Further, for example, in the conventional method, when displaying a red image, the color liquid crystal display panel 110 is set to transmittances of R = 100%, G = 0%, B = 0%, and the backlight has R = G = B =. The utilization factor with respect to the light emission amount is 1/3 at the light emission rate of 100%. However, in this color liquid crystal display device 100, the light emission rate may be R = 100% and G = B = 0%. It is possible to save power by increasing the utilization rate.

  Since it is not actually one point, the control signal creation unit 240 obtains a representative value for the entire screen and sets the backlight RGB value to that value. The video signal side is converted into a value multiplied by the inverse of the backlight side coefficient (considering the LCD filter characteristics).

  That is, according to the conventional concept, as shown in FIGS. 5A and 5B, a color image is displayed by the color liquid crystal display panel 110, and the backlight is illuminated with white light. In the display device 100, as shown in FIGS. 6A and 6B, the backlight device 140 expresses the atmosphere of the entire image excluding the detail portion of the color image as a change in the backlight light source, and displays the color liquid crystal display. The panel 110 displays the difference in light amount between the detail portion of the color image and the backlight.

It is a disassembled perspective view which shows the structure of the transmission type color liquid crystal display device to which this invention is applied. It is a figure which shows the structure of the color filter provided in the liquid crystal display panel with which the said color liquid crystal display device was equipped. It is a figure which shows schematic structure in the backlight housing | casing part in the said transmissive color liquid crystal display device. It is a block diagram which shows the structure of the drive circuit of the said color liquid crystal display device. It is a figure which shows the light emission state of the backlight light source by the backlight apparatus in a color liquid crystal display device provided with the conventional backlight apparatus using CCFL as a backlight light source, and the display state by a color liquid crystal display panel. It is a figure which shows the light emission state of the backlight light source by the backlight apparatus in the said color liquid crystal display device, and the display state by a color liquid crystal display panel.

Explanation of symbols

21R red light emitting diode, 21G green light emitting diode, 21B blue light emitting diode, 21 _n light emitting diode unit, 100 transmissive color liquid crystal display storage, 110 transmissive color liquid crystal display panel, 111 TFT substrate, 112 counter electrode substrate, 113 liquid crystal layer , 131, 132 Polarizing plate, 114 signal line, 115 scanning line, 116 thin film transistor, 117 pixel electrode, 118 counter electrode, 119 color filter, 120 backlight casing, 140 backlight device, 141 diffuser plate, 142 diffuser sheet, 143 prism sheet, 144 polarization conversion sheet, 145 optical sheet group, drive circuit 200, 210 power supply unit, 220 input terminal, 230 video decoder, 240 control signal creation unit, 250 backlight drive control unit, 260 video encoder, 70 X driver circuit, 280 Y driver circuit

Claims (2)

A transmissive color liquid crystal display panel;
A plurality of light emitting diodes that emit at least red light, green light, and blue light, respectively, and a backlight device that illuminates the color liquid crystal display panel from the back side;
Based on the input color video signal, the representative value of the entire image excluding the detail portion of the color image to be displayed is obtained, and the light emission in which the coefficient for controlling the light emission amount of each color of the backlight device is determined according to the value A control signal generator for generating a ratio control video signal by generating a quantity control signal and multiplying the input color video signal by a reciprocal of a coefficient for controlling the light emission amount of each color of the backlight device;
A display panel drive controller for driving the color liquid crystal display panel according to the ratio-converted video signal generated by the control signal generator;
A backlight drive control unit that drives the backlight device in accordance with the light emission amount control signal generated by the control signal generation unit,
With the above backlight device, the atmosphere of the entire image excluding the detail portion of the color image to be displayed is expressed as a change in light amount, and the color liquid crystal display panel displays the difference in light amount between the detail portion of the color image and the backlight. A transmissive color liquid crystal display device. Driving a transmissive color liquid crystal display device that displays a color image by a transmissive color liquid crystal display panel illuminated from the back side by a backlight device comprising a plurality of light emitting diodes that emit at least red light, green light, and blue light, respectively. A method,
Based on the input color video signal, a representative value of the entire image excluding the detail portion of the color image to be displayed is obtained, and a coefficient is determined according to the representative value to control the light emission amount of each color of the backlight device. Thus, the backlight device expresses the atmosphere of the entire image excluding the detail portion of the color image to be displayed as a light amount change,
The color liquid crystal display panel is driven by a ratio-converted video signal obtained by multiplying the input color video signal by a reciprocal of a coefficient for controlling the light emission amount of each color of the backlight device. A method for driving a transmissive color liquid crystal display device, wherein the difference in light quantity between the detail portion and the backlight is displayed.

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