Liquid crystal display device

1. Field of the Invention

The present invention relates to a liquid crystal display device for color displaying. For example, the present invention relates to the liquid crystal display device for the color displaying with a liquid crystal panel having color filters of a vertical-stripe type, a mosaic type or a like built therein, and capable of adjusting white balance of a display screen thereof.

The present application claims priority of Japanese Patent Application No.2000-160804 filed on May 30, 2000, which is hereby incorporated by reference.

2. Description of the Related Art

As shown in FIG. 18, a conventional liquid crystal display device includes: a liquid crystal panel 1 , a signal electrode drive circuit 2 , a scanning electrode drive circuit 3 , and a control circuit 4 . The liquid crystal panel 1 includes color filters where a pixel is divided into sub-pixels of three primary colors of RGB (Red, Green, Blue). The liquid crystal panel 1 also includes: a plurality of data signal lines X 1 , . . . , Xn for receiving a sub-pixel data signal D 2 corresponding to the sub-pixels of RGB, a plurality of scanning signal lines Y 1 , . . . , Ym for receiving a scanning signal V 3 , and a plurality of sub-pixel regions provided at points where each of the data signal lines X 1 , . . . , Xn and each of the scanning signal lines Y 1 , . . . , Ym intersect. The sub-pixel data signal D 2 is supplied to sub-pixel regions selected from the plurality of sub-pixel regions by a scanning signal V 3 , and thus a color image corresponding to the sub-pixel data signal D 2 is displayed.

The signal electrode drive circuit 2 receives a clock signal ck, a control signal Ct, an image signal V 4 for each of RGB, and a central voltage Vs 1 , generates the sub-pixel data signal D 2 by selecting a gradation voltage corresponding to a gradation value of the image signal V 4 for each of RGB, and sends the sub-pixel data signal D 2 to each of the data signal lines X 1 , . . . , Xn of the liquid crystal panel 1 . The scanning electrode drive circuit 3 sends the scanning signal V 3 to each of the scanning signal lines Y 1 , . . . , Ym of the liquid crystal panel 1 synchronously with the clock signal ck. The control circuit 4 outputs the clock signal ck, the control signal Ct, the image signal V 4 , and the central voltage Vs 1 .

FIGS. 19 ( a ), 19 ( b ), and 19 ( c ) are exemplary views showing the above-mentioned color filters used in the liquid crystal panel 1 .

The color filter of a vertical-stripe type shown in FIG. 19 ( a ) is suitable for displaying characters, drawings, and the like. The color filters of a mosaic type and a triangle type shown in FIG. 19 ( b ), and 19 ( c ) are ones where the three primary colors of RGB are arranged in a delta state such as stacked-up bricks, which are suitable for displaying moving images such as television (that is, picture data displaying). There is also a horizontal-stripe type color filter. In the horizontal-stripe type color filter, a horizontal line is constituted of pixels of one of the RGB colors, and a line in the vertical direction is constituted of pixels of the three primary colors of RGB.

Adjustment of white balance of a display screen is generally performed by limiting a range of a gradation value of an image signal for each of RGB to be used. For example, in the case where the gradation value of each of RGB is represented by 8-bit data, the gradation value could take values in a range of from 0 to 256. In adjusting the white balance, however, top and bottom of the gradation value of a particular color are cut. For example, regarding the gradation value for R, 0 to 4 and 251 to 255 are cut, and thus the gradation value of 5 to 25 is used. In addition, regarding the gradation value for G and the gradation value for B, 0 to 255 is used.

In adjusting the white balance, as a method of adjusting the gradation voltage for each of RGB without adjustment of the gradation value for each of RGB, there exists a method described in Japanese Patent Laid-open No. Hei4-60583 gazette (hereinafter, referred to as a literature), for example.

FIG. 20 is a circuit diagram showing an electrical configuration of the signal electrode drive circuit 2 described in the foregoing literature.

The signal electrode drive circuit 2 includes: a serial/parallel conversion circuit 2 a , decoders 2 b 1 , . . . , 2 bn , a color selection circuit 2 c , and selection circuits 2 d 1 , . . . , 2 dn . The serial/parallel conversion circuit 2 a receives the clock signal ck, the control signal Ct and the image signal V 4 , and outputs gradation values V 2 a 1 , . . . , V 2 an for each of RGB of the image signal V 4 . The decoders 2 b 1 , . . . , 2 bn decode the gradation values V 2 a 1 , . . . , V 2 an , and output selection signals S 2 b 1 , . . . , S 2 bn corresponding to the gradation values V 2 a 1 , . . . , V 2 an . The color selection circuit 2 c selects voltages VA, VB, and VC for adjusting the gradation voltage for each of RGB, which are supplied to selected terminals A to C, for every horizontal line period of an image of the liquid crystal panel 1 (FIG. 18) based on a color selection signal CS, and outputs a voltage V 2 c . The selection circuits 2 d 1 , . . . , 2 dn receive drive voltages V 1 , . . . , Vq generated by a voltage dividing resistor connected between the voltage V 2 c and the central voltage Vs 1 , select drive voltages corresponding to the selection signals S 2 b 1 , . . . , S 2 bn from the drive voltages V 1 , . . . , Vq, and output a sub-pixel data signal D 2 .

In the liquid crystal display device, the control circuit 4 outputs the clock signal ck, the control signal Ct, the image signal V 4 , the color selection signal CS and the central voltage Vs 1 . Another control circuit (not shown) outputs the color selection signal CS. The clock signal ck, the control signal Ct, the image signal V 4 for each of RGB and the central voltage Vs 1 are input to the signal electrode drive circuit 2 . Then, gradation voltages corresponding to the gradation value of the image signal V 4 for each of RGB are selected, and the sub-pixel data signal D 2 is generated, which is sent to each of data signal lines X 1 , . . . , Xn of the liquid crystal panel 1 .

In this case, the clock signal ck, the control signal Ct, and the image signal V 4 are input to the serial/parallel conversion circuit 2 a , from which the gradation values V 2 a 1 , . . . , V 2 an of the image signal V 4 for each of RGB are output. The gradation values V 2 a 1 , . . . , V 2 an are input to the decoders 2 b 1 , . . . , 2 bn and decoded, from which selection signals S 2 b 1 , . . . , S 2 bn are output. The voltages VA, VB, and VC supplied to selected terminals A, B, and C are selected for every horizontal line period of the image of the liquid crystal panel 1 in the color selection circuit 2 c based on the color selection signal CS, and the voltage V 2 c is output from the color selection circuit 2 c . The drive voltages V 1 , . . . , Vq are input to the selection circuits 2 d 1 , . . . , 2 dn , and the drive voltage selected based on the selection signals S 2 b 1 , . . . , S 2 bn is output as the sub-pixel data signal D 2 from the selection circuits 2 d 1 , . . . , 2 dn.

In addition, the clock signal ck is input to the scanning electrode drive circuit 3 , the scanning signal V 3 is generated synchronously with the clock signal ck, and the scanning signal V 3 is sent to each of the scanning signal lines Y 1 , . . . , Ym of the liquid crystal panel 1 . In the liquid crystal panel 1 , the sub-pixel data signal D 2 is supplied to the sub-pixel region selected by the scanning signal V 3 , and color image corresponding to the sub-pixel data signal D 2 is displayed. Herein, voltages VA, VB, and VC are adjusted and input in accordance with the color of the color image on the liquid crystal panel 1 , and thus the white balance of the color image is adjusted.

However, in the foregoing conventional general adjustment of the white balance, the use of the gradation value is limited in a particular color. Accordingly, there is a drawback in that combinations of the gradation of RGB, that is, kinds of display colors, are reduced. Moreover, in the method according to the foregoing literature, there is a problem in that the color filter of the liquid crystal panel 1 is limited to the horizontal-stripe type, and it can not deal with the color filters of the vertical stripe type, the mosaic type and the triangle type shown in FIG. 18 .

In view of the above, it is an object of the present invention to provide a liquid crystal display device, in which a color correction voltage for each of RGB is generated, a liquid crystal drive voltage (that is, sub-pixel data signal) is independently generated for each of RGB, and a color image is displayed on a liquid crystal panel, and which can deal with various kinds of color filters.

To solve the above-described problems, according to a first aspect of the present invention, there is provided a liquid crystal display device including a liquid crystal panel for displaying a color image, wherein a color correction voltage generation circuit is provided for generating a color correction voltage for each of RGB based on a given input signal for color correction, and the color correction voltage of each of RGB is added to a gradation voltage of an image signal for each of RGB respectively, then the added voltages are supplied to the liquid crystal panel.

According to a second aspect of the present invention, there is provided a liquid crystal display device, including:

a liquid crystal panel having a plurality of data signal lines for receiving a sub-pixel data signal corresponding to a sub-pixel where a pixel is divided into three primary colors of RGB, a plurality of scanning signal lines for receiving a scanning signal, and a plurality of sub-pixel regions provided at points where each of the data signal lines and each of the scanning signal lines intersect, and the liquid crystal panel displaying a color image corresponding to the sub-pixel data signal by supplying the sub-pixel data signal to a sub-pixel region selected by the scanning signal among the plurality of sub-pixel regions;

a gradation voltage generation circuit for generating a plurality of gradation voltages to give gradation to the sub-pixel data signal;

a color correction voltage generation circuit for generating a color correction voltage for each of RGB based on a given input signal for color correction;

a display signal circuit for selecting a gradation voltage corresponding to a gradation value of an image signal for each of RGB from each gradation voltage, adding the color correction voltage for each of RGB respectively to the gradation voltage to generate the sub-pixel data signal, and sending the sub-pixel data signal to each data signal line of the liquid crystal panel;

a scanning signal circuit for sending the scanning signal to each scanning signal line of the liquid crystal panel synchronously with a clock signal; and

a control circuit for outputting the clock signal and the image signal for each of RGB.

According to a third aspect of the present invention, there is provided a liquid crystal display device, including:

a liquid crystal panel having a plurality of data signal lines for receiving a sub-pixel data signal corresponding to a sub-pixel where a pixel is divided into three primary colors of RGB, a plurality of scanning signal lines for receiving a scanning signal, and a plurality of sub-pixel regions provided at points where each of the data signal lines and each of the scanning signal lines intersect, and the liquid crystal panel displaying a color image corresponding to the sub-pixel data signal by supplying the sub-pixel data signal to a sub-pixel region selected by the scanning signal among the plurality of sub-pixel regions;

a gradation voltage generation circuit for generating a plurality of gradation voltages to give gradation to the sub-pixel data signal, inverting a polarity of the gradation voltage in one frame period based on a polarity inversion signal, and outputting the gradation voltage with the inverted polarity;

a color correction voltage generation circuit for generating a color correction voltage for each of RGB based on a given input signal for color correction, inverting a polarity of the color correction voltage in one frame period based on the polarity inversion signal, and outputting the color correction voltage with the inverted polarity;

a display signal circuit for selecting a gradation voltage corresponding to a gradation value of an image signal for each of RGB from each gradation voltage, adding the color correction voltage for each of RGB respectively to the gradation voltage to generate the sub-pixel data signal, and sending the sub-pixel data signal to each data signal line of the liquid crystal panel;

a scanning signal circuit for sending the scanning signal to each scanning signal line of the liquid crystal panel synchronously with a clock signal; and

a control circuit for outputting the clock signal and the image signal for each of RGB.

According to a fourth aspect of the present invention, there is provided a liquid crystal display device, including:

a liquid crystal panel having a plurality of data signal lines for receiving a sub-pixel data signal corresponding to a sub-pixel where a pixel is divided into three primary colors of RGB, a plurality of scanning signal lines for receiving a scanning signal, and a plurality of sub-pixel regions provided at points where each of the data signal lines and each of the scanning signal lines intersect, and the liquid crystal panel displaying a color image corresponding to the sub-pixel data signal by supplying the sub-pixel data signal to a sub-pixel region selected by the scanning signal among the plurality of sub-pixel regions;

a gradation voltage generation circuit for generating a plurality of gradation voltages to give gradation to the sub-pixel data signal, inverting a polarity of the gradation voltage in a specified number of horizontal line periods based on a polarity inversion signal, and outputting the gradation voltage with the inverted polarity;

a color correction voltage generation circuit for generating a color correction voltage for each of RGB based on a given input signal for color correction;

a polarity inversion circuit for inverting a polarity of the color correction voltage for each of RGB in a specified number of horizontal line periods based on the polarity inversion signal, and outputting the color correction voltage with the inverted polarity;

a display signal circuit for selecting a gradation voltage corresponding to a gradation value of an image signal for each of RGB from each gradation voltage, adding the color correction voltage for each of RGB respectively to the gradation voltage to generate the sub-pixel data signal, and sending the sub-pixel data signal to each data signal line of the liquid crystal panel;

a scanning signal circuit for sending the scanning signal to each scanning signal line of the liquid crystal panel synchronously with a clock signal; and

a control circuit for outputting the clock signal, the image signal for each of RGB, and the polarity inversion signal.

According to a fifth aspect of the present invention, there is provided a liquid crystal display device, including:

a liquid crystal panel having a plurality of data signal lines for receiving a sub-pixel data signal corresponding to a sub-pixel where a pixel is divided into three primary colors of RGB, a plurality of scanning signal lines for receiving a scanning signal, and a plurality of sub-pixel regions provided at points where each of the data signal lines and each of the scanning signal lines intersect, and the liquid crystal panel displaying a color image corresponding to the sub-pixel data signal by supplying the sub-pixel data signal to a sub-pixel region selected by the scanning signal among the plurality of sub-pixel regions;

a gradation voltage generation circuit for generating a plurality of gradation voltages to give gradation to the sub-pixel data signal;

a color correction voltage generation circuit for generating a color correction voltage for each of RGB based on a given input signal for color correction;

a display signal circuit for selecting a gradation voltage corresponding to a gradation value of an image signal for each of RGB from each gradation voltage, inverting the color correction voltage for each of RGB at each sub-pixel based on a polarity inversion signal and adding the color correction voltage with the inverted polarity to the gradation voltage to generate the sub-pixel data signal, and sending the sub-pixel data signal to each data signal line of the liquid crystal panel;

a scanning signal circuit for sending the scanning signal to each scanning signal line of the liquid crystal panel synchronously with a clock signal; and

a control circuit for outputting the clock signal, the image signal for each of RGB, and the polarity inversion signal.

According to a sixth aspect of the present invention, there is provided a liquid crystal display device, including:

a liquid crystal panel having a plurality of data signal lines for receiving a sub-pixel data signal corresponding to a sub-pixel where a pixel is divided into three primary colors of RGB, a plurality of scanning signal lines for receiving a scanning signal, and a plurality of sub-pixel regions provided at points where each of the data signal lines and each of the scanning signal lines intersect, and the liquid crystal panel displaying a color image corresponding to the sub-pixel data signal by supplying the sub-pixel data signal to a sub-pixel region selected by the scanning signal among the plurality of sub-pixel regions;

a gradation voltage generation circuit for generating a plurality of gradation voltages to give gradation to the sub-pixel data signal;

a color correction voltage generation circuit for generating a color correction voltage for each of RGB based on a given input signal for color correction;

a multiplexer for selecting and outputting the color correction voltage for each of RGB in accordance with an arrangement of RGB color filters in a horizontal direction of the sub-pixels on the liquid crystal panel, based on a control signal;

a display signal circuit for selecting a gradation voltage corresponding to a gradation value of an image signal for each of RGB from each gradation voltage, adding the color correction voltage for each of RGB output from the multiplexer respectively to the gradation voltage to generate the sub-pixel data signal, and sending the sub-pixel data signal to each data signal line of the liquid crystal panel;

a scanning signal circuit for sending the scanning signal to each scanning signal line of the liquid crystal panel synchronously with a clock signal; and

a control circuit for outputting the clock signal, the image signal for each of RGB, and the control signal.

With the above configurations, the color correction voltage for each of RGB is added to the gradation voltage for each of RGB. Accordingly, the sub-pixel data signal can be controlled and adjusted independently for each of RGB. Therefore, the white balance can be adjusted without reducing the number of the gradation values. Furthermore, the control circuit for outputting the control signal corresponding to the arrangement of RGB of the sub-pixel and the MUX for selecting and outputting the color correction voltage for each of RGB in accordance with the arrangement of RGB of the sub-pixel of the liquid crystal panel are provided, based on the control signal. Accordingly, the present invention can cope with various color filters.

Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings, in which:

FIG. 1 is a block diagram showing an electrical configuration of a liquid crystal display device according to a first embodiment of the present invention;

FIG. 2 is a circuit diagram showing an electrical configuration of a signal electrode drive circuit 20 shown in FIG. 1;

FIG. 3 is a block diagram showing an electrical configuration of a liquid crystal display device according to a second embodiment of the present invention;

FIG. 4 is a circuit diagram showing an electrical configuration of a signal electrode drive circuit 20 A in FIG. 3;

FIG. 5 is a circuit diagram showing an electrical configuration of a circuit for inverting polarity of a color correction voltage V 60 of an R component in a polarity inversion circuit 70 in FIG. 3;

FIG. 6 is a timing chart showing an operation of the polarity inversion circuit 70 ;

FIG. 7 is a circuit diagram showing a state of the polarity inversion circuit 70 based on FIG. 6;

FIG. 8 is another circuit diagram showing a state of the polarity inversion circuit 70 based on FIG. 6;

FIG. 9 is another circuit diagram showing a state of the polarity inversion circuit 70 based on FIG. 6;

FIG. 10 is still another circuit diagram showing a state of the polarity inversion circuit 70 based on FIG. 6;

FIG. 11 is a block diagram showing an electrical configuration of a liquid crystal display device according to a third embodiment of the present invention;

FIG. 12 is a circuit diagram showing an electrical configuration of a signal electrode drive circuit 2 GB in FIG. 11;

FIG. 13 is a timing chart showing an operation of a polarity inversion circuit 23 j ( 2 k ) in FIG. 12;

FIG. 14 is a block diagram showing an electrical configuration of a liquid crystal display device according to a fourth embodiment of the present invention;

FIG. 15 is a configuration diagram of a MUX 80 in FIG. 14;

FIG. 16 is a circuit diagram showing an electrical configuration of a signal electrode drive circuit 20 C in FIG. 14;

FIG. 17 is a graph explaining an operation of the MUX 80 ;

FIG. 18 is a block diagram showing an electrical configuration of a conventional liquid crystal device;

FIGS. 19 ( a ), 19 ( b ) and 19 ( c ) are exemplary diagrams showing examples of color filters; and

FIG. 20 is a circuit diagram showing an electrical configuration of a signal electrode drive circuit 2 described in a literature.

In driving methods of a liquid crystal display device, there are basic driving methods such as a frame inversion drive, a line inversion drive, and a dot inversion drive. Voltages higher (positive polarity) and lower (negative polarity) than a common voltage (0V) are supplied to the liquid crystal panel as drive voltages, and the liquid crystal panel is driven by an alternating voltage. The drive voltage is generated by allowing a few kinds of gradation voltages generated in the gradation voltage generation circuit to be divided into fragments by a resistor in the signal electrode drive circuit. For example, ten kinds of gradation voltages are generated in the gradation voltage generation circuit, and the gradation voltages are divided by the resistor in the signal electrode drive circuit to generate 128 kinds of gradation voltages. This time, in the case of the dot inversion drive, since the gradation voltages are divided into 64 kinds of gradation voltages above the common voltage and 64 kinds of gradation voltages below the common voltage, the signal electrode drive circuit generates the drive voltage with 64 gradations. In the frame inversion drive and the line inversion drive, either the gradation voltage of positive polarity or the gradation voltage of negative polarity is input to the signal electrode drive circuit. In the dot inversion drive, the gradation voltages of the both polarities are input to the signal electrode drive circuit.

Best modes for carrying out the present invention will be described in further detail using various embodiments with reference to the accompanying drawings.

First Embodiment

FIG. 1 is a block diagram showing an electrical configuration of a liquid crystal display device according to a first embodiment of the present invention.

The liquid crystal display device of this embodiment, as shown in FIG. 1, includes: a liquid crystal panel 10 ; a display signal circuit (for example, a signal electrode drive circuit 20 ); a scanning signal circuit (for example, a scanning electrode drive circuit 30 ); a control circuit 40 ; a gradation voltage generation circuit 50 ; and a color correction voltage generation circuit 60 . The liquid crystal panel 10 has color filters where pixels are divided into sub-pixels of three primary colors of RGB. The liquid crystal panel 10 also includes: a plurality of data signal lines X 1 , . . . , Xn for receiving a sub-pixel data signal D 20 corresponding to the sub-pixels of RGB; a plurality of scanning signal lines Y 1 , . . . , Ym for receiving a scanning signal V 30 ; and a plurality of sub-pixel regions provided at points where each of the data signal lines X 1 , . . . , Xn and each of the scanning signal lines Y 1 , . . . , Ym intersect. The sub-pixel data signal D 20 is supplied to sub-pixel regions selected from the plurality of sub-pixel regions by the scanning signal V 30 , and thus a color image corresponding to the sub-pixel data signal D 20 is displayed.

The signal electrode drive circuit 20 receives a clock signal ck, a control signal Ct, an image signal V 40 for each of RGB, an adding circuit control signal Ca, a plurality of gradation voltages V 50 , and a color correction voltage V 60 , selects a gradation voltage corresponding to a gradation value of the image signal V 40 for each of RGB from each gradation voltage V 50 , adds the color correction voltage V 60 for each of RGB to the gradation voltage to generate the sub-pixel data signal D 20 , and sends the sub-pixel data signal D 20 to each of the data signal lines X 1 , . . . , Xn of the liquid crystal panel 10 . The scanning electrode drive circuit 30 sends the scanning signal V 30 to each of the scanning signal lines Y 1 , . . . , Ym of the liquid crystal panel 10 synchronously with the clock signal ck.

The control circuit 40 outputs the clock signal ck, the image signal V 40 for each of RGB, and the adding circuit control signal Ca. The gradation voltage generation circuit 50 generates a plurality of the gradation voltages V 50 (for example, V 1 , . . . , VQ) for giving gradation to the sub-pixel data signal D 20 . The color correction voltage generation circuit 60 generates the color correction voltage V 60 for each of RGB based on a given input signal “IN” for color correction.

FIG. 2 is a circuit diagram showing an electrical configuration of the signal electrode drive circuit 20 in FIG. 1 .

The signal electrode drive circuit 20 includes: a data register 21 ; a digital/analog converter (hereinafter, referred to as DAC 22 ); and an adding circuit 23 . The data register 21 receives the clock signal ck, the control signal Ct, and the image signal V 40 , and outputs gradation values V 21 - 1 , V 21 - 2 , . . . , V 21 - n of the image signal V 40 for each of RGB. The DAC 22 includes: decoders 22 a 1 , 22 a 2 , . . . , 22 an ; and selection switches 1 - 1 , 1 - 2 , . . . , 1 - 64 , 2 - 1 , 2 - 2 , . . . , 2 - 64 , . . . , n- 1 , n- 2 , . . . , n- 64 , divides the gradation voltages V 50 (V 1 , . . . , VQ) by a voltage dividing resistor circuit (not shown) to generate the gradation voltages V 1 , . . . , V 64 , selects the gradation voltages V 22 - 1 , V 22 - 2 , . . . , V 22 - n corresponding to the gradation values V 21 - 1 , V 21 - 2 , . . . , V 21 - n of the image signal V 40 for each of RGB from the gradation voltages V 1 , . . . , V 64 , and outputs the gradation voltages.

The adding circuit 23 includes: inverters 23 a 1 , 23 a 2 , . . . , 23 an ; switches 23 b 1 , 23 b 2 , . . . , 23 bn ; switches 23 c 1 , 23 c 2 , . . . , 23 cn ; capacitors 23 d 1 , 23 d 2 , . . . , 23 dn ; buffers 23 e 1 , 23 e 2 , . . . , 23 en ; switches 23 f 1 , 23 f 2 , . . . , 23 fn ; switches 23 g 1 , 23 g 2 , . . . , 23 gn ; buffers 23 h 1 , 23 h 2 , . . . , 23 hn ; and capacitors 23 i 1 , 23 i 2 , . . . , 23 in . The adding circuit 23 adds the color correction voltage V 60 (for example, VrR, VrG, VrB) to the gradation voltages V 22 - 1 , V 22 - 2 , . . . , V 22 - n based on the adding circuit control signal Ca, and outputs the sub-pixel data signal D 20 .

Next, an operation of the liquid crystal display device of this embodiment will be described.

The control circuit 40 outputs the clock signal ck, the image signal V 40 for each of RGB and the adding circuit control signal Ca. The gradation voltage generation circuit 50 outputs a plurality of the gradation voltages V 50 (V 1 , . . . , VQ). The color correction voltage generation circuit 60 generates the color correction voltage V 60 for each of RGB based on, for example, the input signal “IN” for color correction given by a user or a like.

The signal electrode drive circuit 20 receives the clock signal ck, the control signal Ct, the image signal V 40 , the adding circuit control signal Ca, the gradation voltage V 50 , and the color correction voltage V 60 , selects the gradation voltage V 50 corresponding to the gradation value of the image signal V 40 for each of RGB from the gradation voltage V 50 , adds the color correction voltage V 60 for each of RGB to the gradation voltage V 50 , and generates the sub-pixel data signal D 20 . The sub-pixel data signal D 20 is sent to each of the data signal lines X 1 , . . . , Xn of the liquid crystal panel 10 .

In this case, data register 21 receives the clock signal ck, the control signal Ct, and the image signal V 40 , and outputs the gradation values V 21 - 1 , V 21 - 2 , . . . , V 21 - n of the image signal V 40 for each of RGB. The DAC 22 receives the gradation values V 21 - 1 , V 21 - 2 , . . . , V 21 - n , selects the gradation voltages V 22 - 1 , V 22 - 2 , . . . , V 22 - n corresponding to the gradation values V 21 - 1 , V 21 - 2 , . . . , V 21 - n from the gradation voltages V 1 , . . . , V 64 , and outputs the gradation voltages. The adding circuit 23 receives the gradation voltages V 22 - 1 , V 22 - 2 , . . . , V 22 - n , adds the color correction voltage V 60 (VrR, VrG, VrB) based on the adding circuit control signal Ca, and outputs the sub-pixel data signal D 20 .

In the adding circuit 23 , in accordance with the adding circuit control signal Ca, the switch 23 b 1 and the switch 23 f 1 become in an OFF state when the switch 23 c 1 and the switch 23 g 1 are in an ON state, and the switch 23 b 1 and the switch 23 f 1 become in an ON state when the switch 23 c 1 and the switch 23 g 1 are in an OFF state. The adding circuit control signal Ca changes its theory level from a low level (hereinafter, referred to as L) to a high level (hereinafter, referred to as H) in one horizontal period. When the switch 23 c 1 and the switch 23 g 1 are in an ON state and the switch 23 b 1 and the switch 23 f 1 are in an OFF state, a voltage Vd 1 a of an electrode “a” of the capacitor 23 d 1 connected to an input side of the buffer 23 e 1 becomes an equal value as the gradation voltage V 22 - 1 . Next, when the switch 23 c 1 and the switch 23 g 1 are in an OFF state and the switch 23 b 1 and the switch 23 f 1 are in an ON state, a voltage Vd 1 b of an electrode “b” of the capacitor 23 d 1 becomes the color correction voltage VrR. Accordingly, the voltage Vd 1 a of the electrode “a” becomes as follows:

Vd 1 a =gradation voltage (V 22 - 1 )+color correction voltage (VrR). The voltage Vd 1 a is output as the sub-pixel data signal D 20 of R component via the buffer 23 h 1 . The sub-pixel data signals D 20 of G component and B component are output in the same manner.

The scanning electrode drive circuit 30 receives the clock signal ck, generates the scanning signal V 30 synchronously with the clock signal ck, and sends the scanning signal V 30 to each of the scanning signal lines Y 1 , . . . , Ym of the liquid crystal panel 10 . In the liquid crystal panel 10 , the sub-pixel data signal D 20 is supplied to a sub-pixel region selected by the scanning signal V 30 , and a color image corresponding to the sub-pixel data signal D 20 is displayed.

As described above, since the first embodiment is designed such that the color correction voltage V 60 for each of RGB (VrR, VrG, VrB) is added to the gradation voltages V 22 - 1 , V 22 - 2 , . . . , V 22 - n , the sub-pixel data signal D 20 is controlled and adjusted independently for each of RGB. Therefore, adjustment of the white balance is enabled without reducing the number of the gradation values of the color image.

Second Embodiment

FIG. 3 is a block diagram showing an electrical configuration of a liquid crystal display device of a line inversion driving method according to the second embodiment of the present invention. Common reference numerals are given to elements common to elements of FIG. 1 showing the first embodiment.

In the liquid crystal display device, a signal electrode drive circuit 20 A, a control circuit 40 A and a gradation voltage generation circuit 50 A having a different configuration are provided instead of a signal electrode drive circuit 20 , a control circuit 40 and a gradation voltage generation circuit 50 shown in FIG. 1, and further, a polarity inversion circuit 70 is also provided. The signal electrode drive circuit 20 A is designed to receive a color correction voltage V 70 instead of a color correction voltage V 60 (FIG. 1) input to the signal electrode drive circuit 20 (FIG. 1 ). The control circuit 40 A has a function to output a polarity inversion signal Cp in addition to the function of the control circuit 40 (FIG. 1 ). The gradation voltage generation circuit 50 A inverts and outputs a polarity of a gradation voltage V 50 , for example, in one horizontal line period, based on the polarity inversion signal Cp. The polarity inversion circuit 70 inverts a polarity of a color correction voltage V 60 for each of RGB in one horizontal line period based on the polarity inversion signal Cp, and outputs the color correction voltage V 70 . Other parts of the configuration are approximately the same as that of FIG. 1; and therefore their description has been omitted.

FIG. 4 is a circuit diagram showing an electrical configuration of the signal electrode drive circuit 20 A in FIG. 3 .

As shown in FIG. 4, the signal electrode drive circuit 20 A has a same electrical configuration as that of a signal electrode drive circuit 20 shown in FIG. 2 . However, the signal electrode drive circuit 20 A is different from the signal electrode drive circuit 20 in that the color correction voltage V 70 is input to an adding circuit 23 instead of the color correction voltage V 60 .

FIG. 5 is a circuit diagram showing an electrical configuration of a circuit for inverting polarity of the color correction voltage V 60 of an R component (of RGB) in the polarity inversion circuit 70 of FIG. 3 .

The polarity inversion circuit 70 includes: a switch 71 , a switch 72 , a buffer 73 , a switch 74 , a capacitor 75 , a switch 76 , switch 77 and a switch 78 . Circuits for inverting polarity of the color correction voltage V 60 of a G component (of RGB) and a B component (of RGB) have the same configuration.

FIG. 6 is a timing chart showing an operation of the polarity inversion circuit 70 . FIG. 7, FIG. 8, FIG. 9 and FIG. 10 are circuit diagrams respectively showing a state of the polarity inversion circuit 70 based on FIG. 6 .

In the operation of the liquid crystal display device of the embodiment, the following point is different from the above-described first embodiment. Specifically, polarity of the color correction voltage V 60 for each of RGB is inverted by the polarity inversion circuit 70 in one horizontal line period based on an adding circuit control signal Ca and a polarity inversion signal Cp, and added to gradation voltages V 22 - 1 , V 22 - 2 , . . . , V 22 - n respectively, and thus a sub-pixel data signal D 20 (FIG. 4) is generated.

In this case, at a time T 1 of FIG. 6, the adding circuit control signal Ca is “L” (Low) and the polarity inversion signal Cp is “H” (High), and thus the polarity inversion circuit 70 is in a state shown in FIG. 7 . Here, a potential of an electrode P 1 of the capacitor 75 is R correction voltage VrR (for example, 1V). At a time T 2 , the adding circuit control signal Ca is “H” and the polarity inversion signal Cp is “H”, and thus the polarity inversion circuit 70 is in a state shown in FIG. 8 . Here, a potential of the electrode P 1 (that is, 1V) of the capacitor 75 is output as the color correction voltage V 70 (that is, 1V) via the switch 72 , the buffer 73 , and the switch 74 . At a time T 3 , the adding circuit control signal Ca is “L” and the polarity inversion signal Cp is “L”, and thus the polarity inversion circuit 70 is in a state shown in FIG. 9 . Here, the color correction voltage V 70 is 0V. At a time T 4 , the adding circuit control signal Ca is “H” and the polarity inversion signal Cp is “L”, and thus the polarity inversion circuit 70 is in a state shown in FIG. 10 . Here, the potential of the electrode P 2 of the capacitor 75 (that is, −1V) is output as the color correction voltage V 70 (that is, −1V) via the switch 72 , the buffer 73 and the switch 74 .

As described above, since the second embodiment is designed such that the color correction voltage V 60 for each of RGB (VrR, VrG, VrB) is inverted in one horizontal line period and added to the gradation voltages V 22 - 1 , V 22 - 2 , . . . , V 22 - n as the color correction voltage V 70 , the sub-pixel data signal D 20 is controlled and adjusted independently for each of RGB. Therefore, similarly to the first embodiment, adjustment of white balance is enabled without reducing the number of a gradation value of a color image.

Third Embodiment

FIG. 11 is a block diagram showing an electrical configuration of a liquid crystal display device of a dot inversion driving method according to the third embodiment of the present invention. Common reference numerals are given to elements common to elements of FIG. 1 showing the first embodiment and elements of FIG. 2 showing the second embodiment and therefore details of them are omitted.

In the liquid crystal display device, a signal electrode drive circuit 20 B of a different configuration is provided instead of a signal electrode drive circuit 20 shown in FIG. 1 . Moreover, the control circuit 40 A identical to that of FIG. 3 is provided instead of a control circuit 40 shown in FIG. 1 . The signal electrode drive circuit 20 B selects a gradation voltage corresponding to a gradation value of an image signal V 40 for each of RGB from a gradation voltage V 50 , inverts a polarity of a color correction voltage V 60 for each of RGB based on an adding circuit control signal Ca and a polarity inversion signal Cp. Then, the color correction voltage V 60 for each of RGB with inverted polarity is respectively added to the gradation voltage to generate a sub-pixel data signal D 20 , and the sub-pixel data signal D 20 is sent to each of data signal lines X 1 , . . . , Xn of the liquid crystal panel. Other parts of the configuration are the same as that of FIG. 1 and their description has been omitted.

FIG. 12 is a circuit diagram showing an electrical configuration of the signal electrode drive circuit 20 B in FIG. 11 . Common reference numerals are given to elements common to elements of FIG. 2 showing the first embodiment.

In signal electrode drive circuit 20 B, DAC 22 B, and adding circuit 23 B having a different configuration are provided instead of a DAC 22 and an adding circuit 23 in FIG. 2 . The DAC 22 B includes: decoders 22 a 1 , 22 a 2 , . . . , 22 an ; and selection switches 1 - 1 , 1 - 2 , . . . , 1 - 128 , 2 - 1 , 2 - 2 , . . . , 2 - 128 , . . . , n- 1 , n- 2 , . . . , n- 128 , divides gradation voltages V 50 (V 1 , . . . , VQ) by a voltage dividing resistor circuit (not shown) to generate gradation voltages V 1 , . . . , V 128 , selects gradation voltages V 22 - 1 , V 22 - 2 , . . . , V 22 - n corresponding to the gradation values V 21 - 1 , V 21 - 2 , . . . , V 21 - n of an image signal V 40 for each of RGB from the gradation voltages V 1 , . . . , V 128 , and outputs selected gradation voltages. As the gradation voltages V 50 (V 1 , . . . , VQ), a voltage of positive polarity and a voltage of negative polarity are supplied, where 0V is a common voltage.

In the adding circuit 23 B, polarity inversion circuits 23 j 1 , 23 j 2 , . . . , 23 jn are added to the adding circuit 23 . Among them, polarity inversion circuits 23 j [ 2 k +1] (where k=0, 1, 2, . . . ) in odd numbers have a configuration same as FIG. 5 showing the second embodiment, invert a polarity of a color correction voltage V 60 for each of RGB at each sub-pixel based on an adding circuit control signal Ca and a polarity inversion signal Cp, and output an output signal V j [ 2 k +1] (where k=0, 1, 2, . . . ). Polarity inversion circuits 23 j [ 2 k ] (where k=1, 2, . . . ) in even numbers are constituted such that an ON/OFF operation of a switch 72 and a switch 77 in FIG. 5 is made to be opposite to that of the polarity inversion circuits 23 j [ 2 k +1]. Other parts of the configuration are approximately same as that of FIG. 2 .

FIG. 13 is a timing chart showing an operation of the polarity inversion circuit 23 j [ 2 k ] in FIG. 12 .

In an operation of the liquid crystal display device of the embodiment, the following point is different from the above-described second embodiment. That is, as shown in FIG. 13, operation of the polarity inversion circuit 23 j [ 2 k ] at a time T 2 and a time T 4 is opposite to operation of polarity inversion circuits 23 j [ 2 k +1] shown in FIG. 5 . Thus, output voltage Vj 2 in antiphase to an output voltage V 70 of a polarity inversion circuit 70 is output. Therefore, polarity of the color correction voltage V 60 for each of RGB is inverted for each sub-pixel based on the adding circuit control signal Ca and the polarity inversion signal Cp, added to the gradation voltages V 22 - 1 , V 22 - 2 , . . . , V 22 - n respectively, and the sub-pixel data signal D 20 is generated.

As described above, since the third embodiment is designed such that the color correction voltage V 60 for each of RGB (VrR, VrG, VrB) is inverted at each sub-pixel and added to the gradation voltages V 22 - 1 , V 22 - 2 , . . . , V 22 - n , the sub-pixel data signal D 20 is controlled and adjusted independently for each of RGB. Therefore, similarly to the first embodiment, adjustment of white balance is enabled without reducing the number of gradation values of a color image.

Fourth Embodiment

The foregoing first, second and third embodiments are described as the liquid crystal display device using the color filter of the vertical stripe type shown in FIG. 18 ( a ). This embodiment is the one that deals with the color filters of the mosaic type, the horizontal stripe type and the like in which the arrangement of the color filters of RGB is repeated at every horizontal line.

FIG. 14 is a block diagram showing an electrical configuration of the liquid crystal display device, which is a fourth embodiment of the present invention. Common reference numerals are given to elements common to elements of FIG. 11 showing the third embodiment.

In the liquid crystal display device of the fourth embodiment, a control circuit 40 B and a signal electrode drive circuit 20 C having a different configuration are provided instead of a control circuit 40 A and a signal electrode drive circuit 20 B in FIG. 11 . In addition, a multiplexer (hereinafter, referred to as a MUX) 80 is provided. The control circuit 40 B has a configuration where the control circuit 40 B has a function to output a control signal S 40 B (FIG. 15) corresponding to an arrangement of RGB of sub-pixels of the liquid crystal panel 10 in addition to a function of the control circuit 40 A. The MUX 80 , as shown in FIG. 15, selects a color correction voltage V 60 for each RGB (VrR, VrG, VrB), based on the control signal S 40 B so as to correspond to a arrangement of RGB of the sub-pixels of the liquid crystal panel 10 , and outputs color correction voltage V 80 (VA, VB, VC) to the signal electrode drive circuit 20 C. Other parts of the configuration are the same as that of FIG. 11 .

FIG. 16 is a circuit diagram showing an electrical configuration of the signal electrode drive circuit 20 C in FIG. 14 .

Although the signal electrode drive circuit 20 C, as shown in FIG. 14, is the electrical configuration similar to the signal electrode drive circuit 20 B, it is different in a point where the color correction voltage V 80 is input to an adding circuit 23 B.

FIG. 17 is a graph explaining an operation of the MUX 80 .

The operation of the liquid crystal display device of FIG. 14 will be described with reference to FIG. 17 .

In the liquid crystal display device, the control signal S 40 B corresponding to the arrangement of RGB of each color filter is output from the control circuit 40 B even in a case where the color filters of the liquid crystal panel 10 are not only of the vertical-stripe type, the mosaic type and the triangle type but also in the horizontal-stripe type. The control signal S 40 B is input to the MUX 80 , the color correction voltage V 80 for each of RGB is selected from the MUX 80 so as to correspond to the arrangement of RGB of the color filter and the selected color correction voltage V 80 is output to the signal electrode drive circuit 20 C.

In this case, as shown in FIG. 17, when the control signal S 40 B corresponds to the color filter of the vertical-stripe type, the color correction voltage V 60 (VA, VB, VC) corresponding to the vertical-stripe type is output from the MUX 80 and sent to the signal electrode drive circuit 20 C. When the control signal S 40 B corresponds to the color filter of the mosaic type, the color correction voltage V 60 (VA, VB, VC) corresponding to the mosaic type is output from the MUX 80 and sent to the signal electrode drive circuit 20 C. When the control signal S 40 B corresponds to the color filter of the horizontal-stripe type, the color correction voltage V 60 (VA, VB, VC) corresponding to the horizontal-stripe type is output from the MUX 80 and sent to the signal electrode drive circuit 20 C. Thereafter, operation similar to the third embodiment is performed.

As described above, in the fourth embodiment, the control circuit 40 B for outputting the control signal S 40 B corresponding to the arrangement of RGB of the sub-pixel and the MUX 80 for selecting and outputting the color correction voltage V 60 of each of RGB so as to correspond to the arrangement of RGB of the sub-pixel of the liquid crystal panel 10 , based on the control signal S 40 B are provided. Accordingly, in addition to the advantages of the third embodiment, the fourth embodiment can be applied to various color filters.

It is apparent that the present invention is not limited to the above embodiments but may be changed and modified without departing from the scope and spirit of the invention.

For example, the color filters are not limited to the three colors of RGB, but may be four colors (for example, including cyan or a like) for example. Moreover, the polarity inversion of the color correction voltage is not limited to the inversion in one horizontal line period, but may be the inversion in two horizontal line periods. Further, the control circuit 40 B and the MUX 80 in FIG. 14 showing the fourth embodiment may be provided in FIG. 1, FIG. 3 or FIG. 11 showing other embodiments.