KR101001993B1 - Liquid crystal display and driving method thereof - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device and a driving method thereof which can improve the brightness and reduce the thickness.

A liquid crystal display device according to the present invention comprises: a liquid crystal display panel in which liquid crystal cells are arranged in a matrix form; A plurality of electro luminescence light sources for generating light of the first to third colors; Time division of one frame period into first to third subframes is performed, and data of first to third colors are sequentially written on the liquid crystal display panel in the first to third subframes, respectively. A driving device for sequentially irradiating the liquid crystal display panel with light of the first to third colors in a third subframe; Light of the first to third colors is generated only during a predetermined period after data is written in each subframe.

Description

Liquid crystal display and its driving method {LIQUID CRYSTAL DISPLAY AND DRIVING METHOD THEREOF}             

1 is a perspective view showing a conventional direct type backlight unit.

2 is a perspective view illustrating a conventional side type backlight unit.

3 is a block diagram illustrating a liquid crystal display device to which the field sequential driving method according to the present invention is applied.

FIG. 4 is a perspective view illustrating the liquid crystal display panel and the EL light source shown in FIG. 3.

FIG. 5 is a waveform diagram illustrating first and second driving signals supplied to the cathode driver and the anode driver illustrated in FIG. 3.

FIG. 6 is a cross-sectional view illustrating a liquid crystal display panel and an EL light source cut along the line "VI-VI '" in FIG. 4.

FIG. 7 is a plan view illustrating the cathode electrode line and the anode electrode line shown in FIG. 6 in detail.

8 is a cross-sectional view illustrating in detail the organic light emitting layer illustrated in FIG. 6.

9 is a waveform diagram illustrating a driving waveform of the liquid crystal display device to which the field sequential driving method according to the present invention is applied.

<Explanation of symbols for the main parts of the drawings>

2: printed circuit board 4: LED array

6: diffuser plate 8: light guide plate

70 hole injection layer 72 hole transport layer

74: light emitting layer 76: electron transport layer

78 electron injection layer 80 liquid crystal display panel

82: data driver 84: gate driver

86: timing control unit 88: cathode driving unit

90: EL light source 92: anode drive unit

101,111,121: substrate 102: black matrix

104: liquid crystal 106: pixel electrode

108: thin film transistor 110: first array substrate

120: second array substrate 122: organic light emitting layer

124: anode electrode line 126: cathode electrode line

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device and a method of driving the same, which can improve the brightness and reduce the thickness thereof.

In general, a liquid crystal display includes a liquid crystal display module and a driving circuit unit for driving the liquid crystal display module.

The liquid crystal display module includes a liquid crystal panel in which liquid crystal cells are arranged in a matrix form between two glass substrates, and a backlight unit that irradiates light to the liquid crystal panel. In addition, in the liquid crystal display module, optical sheets for vertically raising light traveling from the backlight unit toward the liquid crystal panel are arranged. The liquid crystal panel, the backlight unit and the optical sheet must be fastened in an integrated form to prevent light loss and must be protected from damage by external impact. To this end, a case for a liquid crystal display device is formed to surround the backlight unit and the optical sheets including the edge of the liquid crystal panel. Since the liquid crystal display module is not a self-luminous display device, a light source such as a backlight is required. There are two kinds of backlights of the liquid crystal display module, a direct type method shown in FIG. 1 and a side type method shown in FIG. 2.

The direct type backlight unit illustrated in FIG. 1 includes a plurality of LED arrays 4 for generating light and a printed circuit board on which the plurality of LED arrays 4 are mounted at equal intervals. 2) and a diffuser plate 6 for diffusing light emitted from the plurality of LED arrays 4. In the case of such a direct type backlight unit, light emitted from the plurality of LED arrays 4 mounted on the plurality of PCBs 2 is incident on the rear surface of the liquid crystal panel via the diffusion plate 6 and the plurality of optical sheets.                         

The side type backlight unit shown in FIG. 2 includes a plurality of LED arrays 4 for generating light, a PCB 2 on which circuits for controlling light emission of the plurality of LED arrays 4 are mounted, and an LED array 4. The light guide plate 8 for advancing the light incident from the toward the liquid crystal panel is provided. In the case of such a side type backlight unit, light generated in the plurality of LED arrays 4 is incident on the rear surface of the liquid crystal panel via the light guide plate 8 and the plurality of optical sheets.

The liquid crystal display device employing any one of the backlight units shown in FIGS. 1 and 2 does not take advantage of the LCD having a thin thickness because the overall thickness is increased by the backlight unit. In addition, the LED array 4 has a problem that luminance and color unevenness are generated in a light incidence portion close to the LED array 4 and a region far from the LED array 4, resulting in deterioration in image quality. In addition, since the side type backlight unit illustrated in FIG. 2 is located at the side of the light guide plate 8, there is a problem in that the luminance is relatively lowered due to the limitation on the number of uses of the LED array 4.

Accordingly, an object of the present invention is to provide a liquid crystal display device and a driving method thereof which can improve the brightness and reduce the thickness.

In order to achieve the above object, a liquid crystal display device according to an embodiment of the present invention comprises a liquid crystal display panel in which the liquid crystal cells are arranged in a matrix form; A plurality of electro luminescence light sources for generating light of the first to third colors; Time division of one frame period into first to third subframes is performed, and data of first to third colors are sequentially written on the liquid crystal display panel in the first to third subframes, respectively. A driving device for sequentially irradiating the liquid crystal display panel with light of the first to third colors in a third subframe; Light of the first to third colors is generated only during a predetermined period after data is written in each subframe.

The driving device includes: a liquid crystal display panel driving device for driving the liquid crystal display panel by time-dividing one frame period into the first to third subframes; And an electro luminescence driving device for time-divisionally driving the electro luminescence light source.

The driving device of the liquid crystal display panel includes: a data driver for supplying red, green, and blue data to a data line of the liquid crystal display panel within the one frame period; And a gate driver which scans the liquid crystal display panel at least three times within the one frame period.

The liquid crystal display panel includes first and second substrates facing each other with the liquid crystal interposed therebetween; A black matrix formed on the first substrate; A thin film transistor formed on the second substrate so as to overlap the black matrix; And a pixel electrode connected to the thin film transistor.

The electro luminescence light source includes a cathode electrode line formed on the rear surface of the second substrate; A third substrate facing the second substrate; An anode electrode line formed on the third substrate and formed to cross the cathode electrode line; And an organic light emitting layer positioned between the cathode electrode line and the anode electrode line to generate light.                     

The electro luminescence driving apparatus includes an anode driver for supplying a first driving signal to the anode electrode line in each subframe; And a cathode driver configured to supply a second driving signal to the cathode electrode line in each subframe.

Each of the liquid crystal cells may correspond to at least one light source group including three electro luminescence light sources each generating light of the first to third colors.

In order to achieve the above object, the driving method of the liquid crystal display device according to the present invention comprises the steps of generating light of the first to third colors using a plurality of electroluminescent light sources; Time division of one frame period into first to third subframes, and data of first to third colors are sequentially written on the liquid crystal display panel in which liquid crystal cells are arranged in a matrix form in each of the first to third subframes. And sequentially irradiating the liquid crystal display panel with light of the first to third colors in the first to third subframes, respectively. Light of the first to third colors is generated only during a predetermined period after data is written in each subframe.

The sequentially irradiating light of the first to third colors to the liquid crystal display panel may include a first step of supplying a pixel signal to a liquid crystal cell in response to gate pulses sequentially supplied to gate lines for each subframe; ; A second step of holding the pixel signal supplied to the liquid crystal cell; And irradiating the liquid crystal cell with light of a predetermined color generated by the electroluminescent light source.

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The generating of light of the first to third colors using the plurality of electro luminescence light sources may be performed on the first driving signal and the cathode electrode line at the anode electrode line of the electro luminescence light source simultaneously with the third step. And supplying a second driving signal.

Other objects and features of the present invention in addition to the above objects will be apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, a liquid crystal display module according to embodiments of the present invention will be described in detail with reference to FIGS. 3 to 9.

3 is a block diagram illustrating a liquid crystal display device driven by a field sequential driving system according to the present invention.

Referring to FIG. 3, a liquid crystal display according to the present invention includes a liquid crystal panel 80, a data driver 82 for driving data lines DL1 to DLn of the liquid crystal panel 80, and a liquid crystal panel 80. A gate driver 84 for driving the gate lines GL1 to GLm of the light source, an electro luminescence (EL) light source 90 for irradiating light to the liquid crystal panel 80, and A cathode driver 88 for driving the cathode electrode lines CL to CLp of the EL light source 90, an anode driver 92 for driving the anode electrode lines AL1 to ALq of the EL light source 90, A timing controller 86 for controlling the data driver 82, the gate driver 84, the cathode driver 88, and the anode driver 92 is provided.                     

The timing controller 86 supplies the pixel data signals R, G, and B data input from the outside to the data driver 82. In addition, the timing controller 86 includes a gate driver 84, a data driver 82, an anode driver 92, and a cathode driver 88 in response to control signals H, V, DE, and CLK input from the outside. A gate control signal GDC, a data control signal DDC, an anode control signal ADC, and a cathode control signal CDC are generated for controlling each.

The gate control signals GDC include a gate start pulse GSP, a gate shift clock signal GSC, a gate output enable signal GOE, and the like. Among these, the gate start pulse GSP is supplied to the gate line GL three times so that the entire surface can be scanned three times in full within one frame period.

The data control signals DDC include a source start pulse SSP, a source shift clock signal SSC, a source output enable signal SOE, a polarity control signal POL, and the like.

The gate driver 84 sequentially supplies the gate high voltage VGH to the gate lines GL1 to GLm in response to the gate control signals GDC from the timing controller 86. Accordingly, the gate driver 84 causes the thin film transistor TFT connected to the gate lines GL1 to GLm to be driven in units of the gate line GL.

The data driver 82 outputs pixel signals of one horizontal line for each horizontal period H1, H2, ... in response to the data control signals DDC from the timing controller 86. Supplies). In particular, the data driver 82 converts the digital pixel data R, G, and B from the timing controller 86 into an analog pixel signal using a gamma voltage from a gamma voltage generator (not shown). . The data driver 82 time-divides one frame period in which one screen is displayed into first to third subframes to supply data to the data line DL. That is, the data driver 82 sequentially supplies red data to the data line DL during the first subframe period and then supplies green data to the data line DL during the second subframe period. Thereafter, blue data is supplied to the data line DL during the third subframe period.

As shown in FIG. 4, the liquid crystal panel 80 includes a first array substrate 110 and a second array substrate 120 that are formed to face each other with the liquid crystal layer 104 therebetween.

The first array substrate 110 includes a black matrix 102 formed on the first substrate 101. The black matrix 102 is formed to overlap the gate line GL, the data line DL, and the thin film transistor 108 to absorb the light incident from the adjacent cell, thereby preventing the lowering of the contrast.

The second array substrate 120 may include a data line DL and a gate line GL intersecting the second substrate 111 to be insulated on the second substrate 111, and TFTs positioned at intersections thereof. 108 and a thin film transistor array including a pixel electrode 106 formed to be connected to the TFT 108 in the pixel region provided by the data line DL and the gate line GL.

The liquid crystal layer 104 is generated by the EL light source 90 in response to the voltage difference applied to the pixel electrode 106 and the common electrode (not shown), and transmits light transmitted through the second array substrate 120. Will be adjusted.

As shown in FIG. 5, the cathode driver 88 includes the cathode electrode lines CL during the light source lighting period LT of a predetermined subframe among the first to third subframes SF1 to SF3 constituting the first frame. The negative scan pulse, that is, the first driving signal DS1 is sequentially supplied to the first driving signal DS1.

As illustrated in FIG. 5, the anode driver 92 is connected to the anode electrode lines AL during the light source lighting period LT of a predetermined subframe among the first to third subframes SF1 to SF3 constituting the first frame. The second driving signal DS2 is supplied with a current signal having a current level or pulse width corresponding to the light source lighting signal for white balance.

The EL light source 90 includes a red EL light source that emits red, a green EL light source that emits green, and a blue EL light source that emits blue. This EL light source 90 is driven by a field sequential driving method in which a red EL light source, a green EL light source, and a blue EL light source flash sequentially. To this end, the EL light source 90 includes an anode electrode line 124 and a cathode electrode line overlapping the organic light emitting layer 122 with the organic light emitting layer 122 interposed therebetween as shown in FIGS. 6 and 7. 126).

The organic light emitting layer 122 is composed of an organic compound on an insulating film (not shown) defining an opening region. That is, the organic light emitting layer 122 is formed by stacking the hole injection layer 70, the hole transport layer 72, the light emitting layer 74, the electron transport layer 76, and the electron injection layer 78 as shown in FIG. 8. . The organic light emitting layer 122 corresponding to the red EL light source emits red (R), and the organic light emitting layer 122 corresponding to the green EL light source emits green (G), and the organic light emitting layer 122 included in the blue EL light source. ) Emits blue (B).

A plurality of anode electrode lines 124 are spaced apart at predetermined intervals on the third substrate 121. The second driving signal DS2 for emitting holes is supplied to the anode electrode line 124 through the anode driver 92. A plurality of cathode electrode lines 126 are formed on the organic light emitting layer 122 to be spaced apart at predetermined intervals so as to cross the anode electrode lines 124. In addition, a first driving signal DS1 for emitting electrons is supplied to the cathode electrode line 126 through the cathode driver 88.

In the EL light source 90, when a predetermined voltage is applied between the anode electrode line 124 and the cathode electrode line 126, electrons generated from the cathode electrode line 126 are transferred to the electron injection layer 78 and the electron transport layer ( It moves toward the light emitting layer 74 through 76, and holes generated from the anode electrode line 124 move toward the light emitting layer 74 through the hole injection layer 70 and the hole transport layer 72. Accordingly, the light emitting layer 74 emits light by recombination of electrons and holes supplied from the electron transporting layer 76 and the hole transporting layer 72.

10 is a waveform diagram illustrating a driving waveform of the liquid crystal display device to which the field sequential driving method according to the present invention is applied.

As shown in FIG. 10, one frame of the liquid crystal panel is divided into three subframes SF1, SF2, and SF3 that implement red and green blue colors.

In the first subframe SF1, the red data voltage is supplied to the liquid crystal cell using the gate pulse GP during the data write period WT. The red data supplied to the liquid crystal cell is kept constant during the liquid crystal response period AT. In addition, the first driving signal DS1 of the negative polarity is selectively supplied to the cathode electrode line corresponding to the EL light source emitting red light during the light source lighting period LT, and the second driving is supplied to the anode electrode line DL. A positive current according to the signal DS2 is applied to the organic light emitting layer to emit red light. That is, the red EL light source is turned on so that red light is transmitted through the liquid crystal cell supplied with the red data. Accordingly, the red light R is displayed in the liquid crystal cell supplied with the red data in the first subframe SF1 of one frame.

Next, in the second subframe SF2, the green data voltage is supplied to the liquid crystal cell using the gate pulse GP during the data write period WT. The green data supplied to the liquid crystal cell is kept constant during the liquid crystal response period AT. In addition, the first driving signal DS1 of the negative polarity is selectively supplied to the cathode electrode line corresponding to the EL light source emitting green light during the light source lighting period LT, and the second driving is supplied to the anode electrode line DL. A positive current according to the signal DS2 is applied to the organic light emitting layer to emit green light. That is, the green EL light source is turned on so that green light is transmitted through the liquid crystal cell supplied with the green data. Accordingly, green (G) is displayed in the liquid crystal cell to which green data is supplied in the second subframe SF2 of one frame.

Then, in the third subframe SF3, the blue data voltage is supplied to the liquid crystal cell using the gate pulse GP during the data writing period WT. The blue data supplied to the liquid crystal cell is kept constant during the liquid crystal response period AT. In addition, the first driving signal DS1 of the negative polarity is selectively supplied to the cathode electrode line corresponding to the EL light source emitting blue light during the light source lighting period LT, and the second driving is supplied to the anode electrode line DL. A positive current according to the signal DS2 is applied to the organic light emitting layer to emit blue light. That is, the blue EL light source is turned on, and blue light is transmitted through the liquid crystal cell supplied with the blue data. Accordingly, blue (B) is displayed in the liquid crystal cell supplied with blue data in the third subframe SF3 of one frame.

On the other hand, the EL light source group consisting of three EL light sources each of which implements red, green, and blue are located one for each liquid crystal cell or one for each of a plurality of liquid crystal cells within a range in which luminance and color unevenness do not occur. Alternatively, the number of EL light sources that implement red, green, and blue included in the EL light source group may be adjusted to achieve white balance.

As described above, the liquid crystal display device according to the present invention implements an image by using an EL light source. Accordingly, the light guide plate and the plurality of sheets used in the conventional direct type backlight unit or the side type backlight unit can be removed, thereby making the liquid crystal display device thin.

In addition, since the EL light source is uniformly formed under the liquid crystal display panel, the liquid crystal display according to the present invention can prevent the luminance difference and the color unevenness occurring in the light incidence part and the region other than the light incidence part, and use of the lamp Luminance deterioration due to the limitation of the number can be prevented.

In addition, since the EL light source of the liquid crystal display according to the present invention emits light only in the light source lighting section for each subframe of one frame consisting of three subframes, it is possible to prevent deterioration of the life of the EL light source.                     

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (12)

A liquid crystal display panel in which liquid crystal cells are arranged in a matrix form; A plurality of electro luminescence light sources for generating light of the first to third colors; Time division of one frame period into first to third subframes is performed, and data of first to third colors are sequentially written on the liquid crystal display panel in the first to third subframes, respectively. A driving device for sequentially irradiating the liquid crystal display panel with light of the first to third colors in a third subframe; And the light of the first to third colors is generated only for a predetermined period after data is written in each subframe. The method of claim 1, The drive device, A liquid crystal display panel driving device for time-dividing one frame period into the first to third subframes to drive the liquid crystal display panel; And an electro luminescence driving device for time-divisionally driving the electro luminescence light source. The method of claim 2, The driving device of the liquid crystal display panel A data driver for supplying red, green, and blue data to a data line of the liquid crystal display panel within the one frame period; And a gate driver for scanning the entire liquid crystal display panel at least three times in one frame period. The method of claim 2, The liquid crystal display panel First and second substrates facing each other with the liquid crystal interposed therebetween; A black matrix formed on the first substrate; A thin film transistor formed on the second substrate so as to overlap the black matrix; And a pixel electrode connected to the thin film transistor. The method of claim 4, wherein The electro luminescence light source is A cathode electrode line formed on a rear surface of the second substrate; A third substrate facing the second substrate; An anode electrode line formed on the third substrate and formed to cross the cathode electrode line; And an organic light emitting layer positioned between the cathode electrode line and the anode electrode line to generate light. The method of claim 5, The electro luminescence drive device An anode driver for supplying a first driving signal to the anode electrode line in each subframe; And a cathode driver for supplying a second driving signal to the cathode electrode line in each subframe. The method of claim 1, Wherein each of the liquid crystal cells corresponds to at least one light source group including three electro luminescence light sources each generating light of the first to third colors. Generating light of the first to third colors using a plurality of electro luminescence light sources; Time division of one frame period into first to third subframes, and data of first to third colors are sequentially written on the liquid crystal display panel in which liquid crystal cells are arranged in a matrix form in each of the first to third subframes. And sequentially irradiating the liquid crystal display panel with light of the first to third colors in the first to third subframes, respectively. The light of the first to third colors is generated only during a predetermined period after data is written in each subframe. delete The method of claim 8, Irradiating the light of the first to third colors to the liquid crystal display panel sequentially, A first step of supplying a pixel signal to a liquid crystal cell in response to a gate pulse sequentially supplied to a gate line for each subframe; A second step of holding the pixel signal supplied to the liquid crystal cell; And irradiating the liquid crystal cell with light of a predetermined color generated by the electro luminescence light source. The method of claim 10, Generating light of the first to third colors by using the plurality of electro luminescence light sources And simultaneously supplying a first driving signal to an anode electrode line of the electro luminescence light source and a second driving signal to a cathode electrode line at the same time as the third step. The method of claim 8, Wherein each of the liquid crystal cells corresponds to at least one light source group consisting of three electro luminescence light sources each generating light of the first to third colors.

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