KR20080023076A - Display device and the driving method thereof - Google Patents

Abstract

A display device and a method for driving the same are provided to enhance the dynamic contrast by using a display panel having a low resolution as a backlight unit, thereby improving the display quality. A panel assembly(10) includes a plurality of first gate lines for transmitting a first gate signal, a plurality of first data lines for transmitting a first data signal, and a plurality of first pixels each having a pixel circuit. The first pixels are defined by the first gate lines and the first data lines. A backlight unit(40) includes a plurality of second gate lines for transmitting a second gate signal, a plurality of second data lines for transmitting a second data signal, and a plurality of second pixels. The second pixels are defined by the second gate lines and the second data lines. Each of the second pixels corresponds to at least two of the first pixels, and emits light correspondingly to the highest of gray levels of the at least two of the first pixels.

Description

DISPLAY DEVICE AND THE DRIVING METHOD THEREOF}

1 is an exploded perspective view of a liquid crystal display according to an exemplary embodiment of the present invention.

FIG. 2 is a partially cutaway perspective view of the liquid crystal panel assembly shown in FIG. 1.

3 is a partially cutaway perspective view of the backlight unit according to the first embodiment of the present invention.

4 is a partial cross-sectional view of the fourth substrate and the electron emission unit illustrated in FIG. 3.

5 is a partial plan view of an electron emission unit of a backlight unit according to a second embodiment of the present invention.

6 is a partially cutaway perspective view of a backlight unit according to a third exemplary embodiment of the present invention.

7 is a diagram illustrating a display device according to an exemplary embodiment of the present invention.

8 illustrates driving waveforms of the liquid crystal display according to the exemplary embodiment of the present invention.

The present invention relates to a display device, and more particularly, to a display device including a backlight unit operating in synchronization with a display image.

A liquid crystal display device, which is a type of flat panel display device, is a display device that realizes a predetermined image by varying light transmittance for each pixel by using dielectric anisotropy of a liquid crystal whose twist angle changes according to an applied voltage. Such a liquid crystal display device has advantages such as light weight, thickness, and low power consumption compared to a cathode ray tube, which is a typical image display device.

The liquid crystal display basically includes a liquid crystal panel assembly and a backlight unit positioned behind the liquid crystal panel assembly to provide light to the liquid crystal panel assembly.

When composed of a liquid crystal panel assembly capable of a liquid crystal panel assembly, the liquid crystal panel assembly includes a pair of transparent substrates, a liquid crystal layer positioned between the transparent substrates, a polarizing plate disposed on the outer surfaces of the transparent substrates, and either transparent A color filter that provides red, green, and blue colors to the common electrode provided on the inner surface of the substrate, the pixel electrodes and switching elements provided on the inner surface of the other transparent substrate, and the three sub-pixels constituting one pixel. And the like.

The liquid crystal panel assembly receives light emitted from the backlight unit and transmits or blocks the light by the action of the liquid crystal layer to realize a predetermined image.

The backlight unit may be classified according to the type of light source, and one of them is known as a cold cathode fluorescent lamp (CCFL). Since the CCFL is a line light source, the light generated from the CCFL can be evenly distributed toward the liquid crystal panel assembly through the optical members such as the diffusion sheet, the diffusion plate, and the prism sheet.

However, in the CCFL method, since light generated in the CCFL passes through the optical member, significant light loss occurs. In general, in the CCFL type liquid crystal display, the light passing through the liquid crystal panel assembly is known to correspond to about 3 to 5% of the CCFL generated light. In addition, the CCFL type backlight unit consumes a large portion of the total power consumption of the liquid crystal display due to large power consumption, and it is difficult to apply to a large liquid crystal display device having a size of 30 inches or more because of the large area of the CCFL structure.

As a conventional backlight unit, a light emitting diode (LED) method is known. A plurality of LEDs are usually provided as a point light source, and are combined with optical members such as a reflective sheet, a light guide plate, a diffusion sheet, a diffusion plate, and a prism sheet to constitute a backlight unit.

This LED method has the advantages of fast response speed and excellent color reproducibility, but has a disadvantage of high price and large thickness.

As such, the conventional backlight unit has its own problems depending on the type of light source. In addition, since the conventional backlight unit is always turned on at a constant brightness when the liquid crystal display is driven, it is difficult to meet the image quality improvement required for the liquid crystal display.

For example, when the liquid crystal panel assembly displays an arbitrary screen including a bright portion and a dark portion in accordance with an image signal, the backlight unit displays the liquid crystal panel pixels portion displaying the bright portion and the liquid crystal panel pixels displaying the dark portion. If the light of different intensity is provided to the part, it is possible to realize a screen having excellent dynamic contrast.

However, the above-described backlight unit cannot implement the above functions, and thus the conventional liquid crystal display has a limitation in increasing the dynamic contrast ratio of the screen.

Accordingly, an object of the present invention is to provide a liquid crystal display and a driving method thereof capable of realizing excellent screen quality by increasing a dynamic contrast ratio of a screen.

Another object of the present invention is to provide a liquid crystal display and a driving method thereof capable of reducing power consumption of a backlight unit and minimizing light loss by an optical member.

In order to achieve the above object, a display device according to an aspect of the present invention includes a plurality of first scan lines for transmitting a first scan signal, a plurality of first data lines for transferring a first data signal, and a first scan line; A panel assembly including a plurality of first pixels defined by the first data line and having respective pixel circuits, a plurality of second scan lines for transmitting a second scan signal, and a plurality of second lines for transmitting a second data signal And a backlight unit including a data line and a plurality of second pixels defined by the second scan line and the second data line, wherein the second pixel is at least two first pixels of the plurality of first pixels. Corresponds to the highest gray level among the at least two first pixels. The second pixel is a field emission array type electron emission device, which includes a cathode electrode and a gate electrode, emits light by a voltage difference between the gate electrode and the cathode electrode, and the second scan signal is transmitted to the gate electrode. The second data signal is applied to the cathode. The second scan signal transmitted to the second pixel corresponding to the at least two first pixels is transmitted to the second scan line during a first period in which the first scan signal corresponding to the at least two first pixels is transmitted. The second data signal applies a second data signal corresponding to the highest gray level to the second pixel in response to a time point at which the first data signal of the at least two first pixels is applied. When the first data signal of the at least two first pixels is applied, the second data signal is applied to the cathode as a cathode voltage for displaying the highest gray scale. The backlight unit generates a light emitting signal for displaying a gray level corresponding to the highest gray level among the at least two first pixels on the second pixel, and a cathode voltage for displaying the highest gray level is applied to the light emitting signal. Corresponds. The light emission signal is at least 6 bits of digital data.

The second scan signal transmitted to the second pixel corresponding to the at least two first pixels is the second scan line during a first period in which the first scan signal corresponding to the at least two first pixels is transmitted. The second data signal is transmitted to the second data signal, the second data signal corresponding to a time point at which the first first data signal of the at least two first pixels is applied, and the second data signal is constant during a period corresponding to the highest gray level of the at least two first pixels. 2 data signals are applied to the light emitting pixels. The second data signal is synchronized with a point in time at which the first data signal of the at least two first pixels is applied, so that the second data signal is supplied to the second pixel as a constant cathode voltage for a period corresponding to the highest gray level. Is authorized. The backlight unit generates a light emitting signal for displaying a gray level corresponding to the highest gray level among the at least two first pixels on the second pixel, and a period corresponding to the highest gray level corresponds to the light emitting signal. It is a period. The light emission signal is at least 6 bits of digital data.

A method of driving a display device according to another aspect of the present invention, comprising: a plurality of first scan lines transferring a first selection signal, a plurality of first data lines transferring a first data signal, and the first scan line and the A panel assembly including a plurality of first pixels defined by a first data line and having a respective pixel circuit, a plurality of second scan lines for transmitting a second selection signal, and a plurality of second for transmitting a second data signal A data line, and a plurality of second pixels defined by the second scan line and the second data line, wherein the second pixel corresponds to at least two first pixels of the plurality of first pixels. A driving method of a display device including a light unit includes (a) a second scan of the second pixel corresponding to the first pixels during a first period in which a first selection signal is transmitted to the at least two first pixels. Transmitting the second selection signal to a line; and (b) the second data on the second data line of the second pixel corresponding to a time point at which the first first data signal of the at least two first pixels is applied. Transmitting a signal. And (c) detecting the highest gray level among the at least two first pixels, and the step (b) applies a second data signal corresponding to the detected gray level to the second pixel. (D) generating a light emission signal for displaying a gray level corresponding to the highest gray level among the at least two first pixels on the second pixel, wherein the second data signal of step (b) Has a voltage corresponding to the light emission signal. At this time, the light emission signal is at least 6 bits of digital data.

And (c) detecting the highest gray level of the at least two first pixels, wherein (b) the second data signal is constant during a first period corresponding to the detected gray level. Applied to the pixel. (D) generating a light emission signal for displaying a gray level corresponding to the highest gray level among the at least two first pixels on the second pixel, wherein the first period of the step (b) is It corresponds to the light emission signal. At this time, the light emission signal is at least 6 bits of digital data.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention. Like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is "connected" to another part, this includes not only the "directly connected" but also the "electrically connected" between other elements in between. In addition, when a part is said to "include" a certain component, it means that it may further include other components, except for the other components unless otherwise stated.

1 is an exploded perspective view of a liquid crystal display according to an exemplary embodiment of the present invention.

Referring to the drawings, the liquid crystal display device 100 of the present embodiment has a liquid crystal panel assembly 10 having arbitrary pixels along the row direction and the column direction, and smaller than the liquid crystal panel assembly 10 along the row direction and the column direction. And a backlight unit 40 having a number of pixels and positioned behind the liquid crystal panel assembly 10 to provide light to the liquid crystal panel assembly 10.

Here, the row direction may be defined as one direction of the liquid crystal display 100, for example, a horizontal direction of the screen implemented by the liquid crystal panel assembly 10 (for example, the x-axis direction in the drawing), and the column direction may be defined as the liquid crystal display. Another direction of 100 may be defined as, for example, a vertical direction (for example, y-axis direction in the drawing) of the screen implemented by the liquid crystal panel assembly 10.

The number of pixels of the liquid crystal panel assembly 10 and the number of pixels of the backlight unit 40 in the row direction are referred to as M and M ', respectively, and the number of pixels and the backlight unit of the liquid crystal panel assembly 10 in the column direction ( When the number of pixels 40 is N and N ', respectively, the resolution of the liquid crystal panel assembly 10 may be expressed as M ㅧ N, and the resolution of the backlight unit 40 may be expressed as M' ㅧ N '.

In the present exemplary embodiment, M and N representing the number of pixels of the liquid crystal panel assembly 10 may be defined as integers of 240 or more, respectively, and M 'and N' representing the number of pixels of the backlight unit 40 are 2 to 99, respectively. Can be defined as any one of the integers. The backlight unit 40 includes a self-luminous display panel having a resolution of M 'ㅧ N'.

Thus, one pixel of the backlight unit 40 is positioned corresponding to two or more pixels of the liquid crystal panel assembly 10. In addition, the pixels of the backlight unit 40 are individually controlled on / off and light emission intensity by driving electrodes arranged in a matrix form, for example, scan electrodes and data electrodes positioned in directions perpendicular to each other.

In this embodiment, one pixel of the backlight unit 40 is formed of a field emission array (FEA) type electron emission device.

The FEA type electron emission device includes a scan electrode and a data electrode, an electron emission part and a fluorescent layer electrically connected to any one of the scan electrode and the data electrode. The electron emission part may be made of a material having a low work function or a high aspect ratio, for example, a carbon-based material or a nanometer (nm) size material.

The FEA type electron emitting device forms an electric field around the electron emitting part by using the voltage difference between the scan electrode and the data electrode to emit electrons therefrom, and excites the fluorescent layer with the emitted electrons to display visible light having an intensity corresponding to the electron beam emission amount. Release.

FIG. 2 is a partially cutaway perspective view of the liquid crystal panel assembly shown in FIG. 1.

Referring to the drawings, the liquid crystal panel assembly 10 includes a transparent first substrate 12 and a second substrate 14 disposed opposite to each other, and a liquid crystal injected between the first substrate 12 and the second substrate 14. A layer 16, a common electrode 18 located on an inner surface of the first substrate 12, pixel electrodes 20 and switching elements 22 located on an inner surface of the second substrate 14. do. Sealing members (not shown) are positioned at edges of the first substrate 12 and the second substrate 14.

The first substrate 12 is the front substrate of the liquid crystal panel assembly 10, and the second substrate 14 is the rear substrate of the liquid crystal panel assembly 10. On the outer surface of the first substrate 12 and the second substrate 14, a pair of polarizing plates 24, 26 whose polarization axes are perpendicular to each other are positioned. The inner surface of the first substrate 12 on which the common electrode 18 is located and the inner surface of the second substrate 14 on which the pixel electrodes 20 and the switching elements 22 are positioned are covered with the alignment layer 28. .

On the inner surface of the second substrate 14, a plurality of gate lines 30 for transmitting a gate signal (also referred to as a "scan signal") and a plurality of data lines 32 for transmitting a data signal are formed. The gate lines 30 are located next to each other along the row direction, and the data lines 32 are located next to each other along the column direction.

One pixel electrode 20 is positioned for each sub-pixel, and each sub-pixel includes a switching element 22 connected to the gate line 30 and a data line 32, and a liquid crystal connected to the switching element 22. Capacitor Clc (not shown) and sustain capacitor Cst (not shown) are formed. Holding capacitor Cst can be omitted as needed.

The switching element 22 may be formed of a thin film transistor, the control terminal and the input terminal of which are connected to the gate line 30 and the data line 32, respectively, and the output terminal of which is connected to the liquid crystal capacitor Clc.

The color filter 34 is disposed between the first substrate 12 and the common electrode 18. The color filter 34 is composed of red, green, and blue filters corresponding to one sub-pixel, and three sub-pixels in which three filters of red, green, and blue are located constitute one pixel.

When the thin film transistor, which is the switching element 22, is turned on in the liquid crystal panel assembly 10 having the above-described configuration, an electric field is formed between the pixel electrode 20 and the common electrode 18. The twist angle of the liquid crystal molecules positioned in the liquid crystal layer 16 is changed by this electric field to control a light transmission amount for each sub-pixel, thereby implementing a predetermined color image.

A first embodiment of the backlight unit will be described with reference to FIGS. 3 and 4, and a second embodiment of the backlight unit will be described with reference to FIG. 5. In both embodiments, the backlight unit consists of an FEA type electron emission display panel including FEA type electron emission elements.

3 is a partial cutaway perspective view of the backlight unit according to the first embodiment, and FIG. 4 is a partial cross-sectional view of the fourth substrate and the electron emission unit illustrated in FIG. 3.

Referring to the drawings, the backlight unit 40 includes a third substrate 42 and a fourth substrate 44 which are disposed to face each other at a predetermined interval. The sealing member 46 is disposed at the edge of the third substrate 42 and the fourth substrate 44 to bond the two substrates, and the internal space is evacuated with a vacuum of approximately 10-6 Torr, so that the third substrate 42 The fourth substrate 44 and the sealing member 46 constitute a vacuum container.

The third substrate 42 becomes the front substrate of the backlight unit 40 facing the liquid crystal panel assembly, and the fourth substrate 44 becomes the rear substrate of the backlight unit 40. One surface of the fourth substrate 44 facing the third substrate 42 is provided with an electron emission unit 48 for electron emission, and one surface of the third substrate 42 facing the fourth substrate 44 is a light emitting unit. 50 is provided.

First, the electron emission unit 48 will be described. The electron emission unit 48 may include the cathode electrodes 52 formed in a stripe pattern along one direction of the fourth substrate 44 and the insulating layer 54. The gate electrodes 56 are formed in a stripe pattern in a direction orthogonal to the cathode electrode 52, and the electron emission units 58 electrically connected to the cathode electrode 52.

The gate electrodes 56 may be arranged side by side in the row direction of the fourth substrate 44, and may function as scan electrodes by applying a scan driving voltage. The cathode electrodes 52 may be arranged side by side in the column direction of the fourth substrate 44, and may function as a data electrode by receiving a data driving voltage.

Electron emitters 58 are formed in the cathode electrode 52 at each intersection of the cathode electrode 52 and the gate electrode 56. Openings 541 and 561 corresponding to the electron emission portions 58 are formed in the insulating layer 54 and the gate electrodes 56 to expose the electron emission portions 58 on the fourth substrate 44. In this embodiment, the intersection area of the cathode electrode 52 and the gate electrode 56 corresponds to one pixel area of the backlight unit 40.

The electron emission unit 58 is made of materials that emit electrons when an electric field is applied in a vacuum, such as a carbon-based material or a nanometer (nm) size material. The electron emission unit 58 may include, for example, carbon nanotubes, graphite, graphite nanofibers, diamonds, diamond-like carbons, C60, silicon nanowires, or a combination thereof, and may be screen printed or directly grown. , Chemical vapor deposition or sputtering, and the like.

On the other hand, the electron emission portion may be formed of a tip structure having a pointed tip mainly made of molybdenum (Mo) or silicon (Si).

Next, the light emitting unit 50 provided on the third substrate 42 includes a fluorescent layer 60 and an anode electrode 62 positioned on one surface of the fluorescent layer 60. The fluorescent layer 60 may be formed of a white fluorescent layer or a combination of red, green, and blue fluorescent layers. In the figure, the first case is illustrated.

The white fluorescent layer may be formed on the entirety of the third substrate 42 or may be divided and positioned in a predetermined pattern so that one white fluorescent layer is positioned in each pixel area. The red, green, and blue fluorescent layers may be divided and positioned in a predetermined pattern in one pixel area.

The anode electrode 62 may be formed of a metal film such as aluminum (Al) covering the surface of the fluorescent layer 60. The anode electrode 62 is an acceleration electrode for attracting an electron beam, and is applied with a high voltage (a positive DC voltage of approximately several thousand volts) to maintain the fluorescent layer 60 in a high potential state, and among the visible light emitted from the fluorescent layer 60. The visible light emitted toward the fourth substrate 44 is reflected toward the third substrate 42 to increase the brightness of the screen.

In the above-described configuration, the FEA type electron emission device includes a cathode electrode 52, a gate electrode 56, electron emission portions 58, and a corresponding fluorescent layer 60 constituting one pixel.

In the above configuration, when a predetermined driving voltage is applied to the cathode electrodes 52 and the gate electrodes 56, an electric field is formed around the electron emission section 58 in the pixel region in which the voltage difference between the two electrodes is greater than or equal to the threshold. Electrons are emitted. The emitted electrons are attracted by the high voltage applied to the anode electrode 62 and collide with the corresponding fluorescent layer 60 to emit light. The emission intensity of the pixel-specific fluorescent layer 60 corresponds to the electron beam emission amount of the pixel.

5 is a partial plan view of the electron emission unit 48 'of the backlight unit according to the second embodiment.

Referring to the drawings, in this embodiment, two or more intersection regions of the cathode electrode 52 'and the gate electrode 56' are combined to form one pixel region A. Referring to FIG. In this case, when two or more cathode electrodes 52 'and two or more gate electrodes 56' are combined to form one pixel region A, the two or more cathode electrodes 52 'are formed. Electrically connected to each other to receive the same driving voltage, two or more gate electrodes 56 'are also electrically connected to each other to receive the same driving voltage.

To this end, the two or more cathode electrodes 52 ′ and the two or more gate electrodes 56 ′ extend to the edge of the fourth substrate to form a connection member such as a flexible printed circuit board (FPCB). Ends (not shown) may be connected to each other.

In the drawing, as an example, nine crossing regions where three cathode electrodes 52 'and three gate electrodes 56' intersect form one pixel region A is illustrated.

In both the back light unit of the first embodiment and the back light unit of the second embodiment, the compression force applied to the vacuum container is supported between the third substrate 42 and the fourth substrate 44 and the distance between the two substrates is maintained. Spacers 64 (see Fig. 4) are arranged to keep the constant. The spacers 64 are preferably located outside the pixel area, not in the center of the pixel area.

In addition, if necessary, the third substrate 42 itself, which is a front substrate, may have a light diffusing function to function as a diffusion plate, and as shown in FIG. 6, an outer surface of the third substrate 42 facing the liquid crystal panel assembly. A diffuser plate 66 having a light diffusing function may be located in the.

As described above, the liquid crystal display 100 of the present exemplary embodiment uses a kind of low resolution display panel having a smaller number of pixels than the liquid crystal panel assembly 10 as the backlight unit 40. The backlight unit 40 is driven through a passive matrix method using scan electrodes and data electrodes, and provides light of different intensities to pixels of the liquid crystal panel assembly 10 corresponding to each pixel. .

The following table tests the display quality, the manufacturing cost of the driving circuit portion, the ease of manufacture, etc. while changing the number of pixels of the backlight unit 40 for the liquid crystal panel assembly 10 having an arbitrary resolution, and is derived according to the result. The optimal number of pixels of the backlight unit 40 for each resolution of the liquid crystal panel assembly 10 is shown.

Based on the above results, it can be seen that (liquid crystal panel assembly pixel number) / (backlight unit pixel number) is preferably in the range of 240 to 5,852. If the value exceeds 5,852, the effect of improving the dynamic contrast ratio by the backlight unit is insufficient, and if the value is less than 240, the manufacturing and driving of the backlight unit becomes difficult, thereby increasing the manufacturing cost.

In addition, in the present embodiment, one pixel of the backlight unit 40 may be formed to have a size of 2 to 50 mm along the row direction and / or the column direction. If the pixel size in the row direction and / or column direction is less than 2 mm, the backlight unit 40 has a considerable number of pixels, which makes it difficult to process the circuit signal, and the pixel size in the row direction and / or column direction On the contrary, if the amount exceeds 50 mm, the backlight unit 40 has a too small number of pixels, and the image quality improvement effect of the backlight unit 40 is insufficient.

As described above, the liquid crystal display device 100 according to the present embodiment uses the backlight unit 40 having the above-described configuration, and thus, a conventional cold cathode fluorescent lamp (hereinafter referred to as 'CCFL') and a light emitting diode (hereinafter referred to as 'LED'). Compared with the backlight unit of the type, it has the following advantages.

Since the backlight unit 40 of the present embodiment is a surface light source, it does not require a plurality of optical members used for the CCFL type backlight unit and the LED type backlight unit. Therefore, in the backlight unit 40 of the present embodiment, almost no light loss occurs while passing through the optical member, and the light unit 40 does not have to emit light of excessive intensity in consideration of the light loss. Efficiency can be obtained.

In addition, the backlight unit 40 of the present embodiment has a lower power consumption than the CCFL type back light unit, and can reduce the cost by not using the optical member. Low cost In addition, the backlight unit 40 of the present embodiment can be easily applied to a large liquid crystal display device of 30 inches or more because it is easy to enlarge the size.

7 is a block diagram illustrating a display device according to an exemplary embodiment of the present invention. A display device according to an exemplary embodiment of the present invention describes a display device using a liquid crystal panel assembly. However, the present invention is not limited thereto.

As shown in FIG. 7, the display device according to the exemplary embodiment of the present invention includes a liquid crystal panel assembly 10, a gate driver 102 and a data driver 104 connected to the liquid crystal panel assembly 10, and a data driver ( And a gray voltage generator 106 connected to 104, a backlight unit 40 ', and a signal controller 108 for controlling them.

The liquid crystal panel assembly 10 includes a plurality of signal lines G1 -Gn and D1-Dm as viewed in an equivalent circuit, and a plurality of pixels PX connected to the signal lines and arranged in a substantially matrix form. do. The signal lines G1 -Gn and D1 -Dm may include a plurality of gate lines G1 -Gn that transfer gate signals (also referred to as "scan signals"), and a plurality of data lines D1 -Dm that transfer data signals. Include.

Connected to each pixel PX, for example, the i-th (i = 1,2, ... n) gate line Gi and the j-th (j = 1,2, ... m) data line Dj The pixel 11 includes a switching element Q connected to signal lines Gi and Dj, a liquid crystal capacitor Clc, and a storage capacitor Cst connected thereto. Holding capacitor Cst can be omitted as needed.

The switching element Q is a three-terminal element such as a thin film transistor provided on a lower substrate (not shown), the control terminal of which is connected to the gate line Gi, and the input terminal of which is connected to the data line Dj. The output terminal is connected to the liquid crystal capacitor Clc and the storage capacitor Cst.

The gray voltage generator 106 generates two sets of gray voltages (or a set of reference gray voltages) related to the transmittance of the pixel PX. One of the two sets has a positive value for the common voltage Vcom, and the other set has a negative value.

The gate driver 102 is connected to the gate lines G1 -Gn of the liquid crystal panel assembly 10 to receive a gate signal formed of a combination of the gate on voltage Von and the gate off voltage Voff. To apply.

The data driver 104 is connected to the data lines D1-Dm of the liquid crystal panel assembly 10, selects a gray voltage from the gray voltage generator 106, and uses the data driver 104 as a data signal to the data lines D1-Dm. Is authorized. However, when the gray voltage generator 106 provides only a predetermined number of reference gray voltages instead of providing all of the voltages for all grays, the data driver 104 divides the reference gray voltages and thus the gray voltages for all grays. Generate and select the data signal from it.

The signal controller 108 controls the gate driver 102, the data driver 104, the backlight unit controller 110, and the like. The signal controller 108 receives an input image signal R, G, B and an input control signal for controlling the display thereof from an external graphic controller (not shown).

The input image signals R, G, and B contain luminance information of each pixel PX, and luminance has a predetermined number, for example, 1024 (= 210), 256 (= 28) or 64 (= 26). It has) grays. Examples of the input control signal include a vertical sync signal Vsync, a horizontal sync signal Hsync, a main clock MCLK, and a data enable signal DE.

The signal controller 108 appropriately processes the input image signals R, G, and B based on the input image signals R, G, and B and the input control signals according to the operating conditions of the liquid crystal panel assembly 10, and controls the gate. After generating the signal CONT1 and the data control signal CONT2, the gate control signal CONT1 is sent to the gate driver 102, and the data control signal CONT2 and the processed image signal DAT are transmitted to the data driver 104). In addition, the signal controller 108 transmits the gate control signal CONT1, the data control signal CONT2, and the processed image signal DAT to the backlight unit controller 110. The gate control signal CONT1 according to the embodiment of the present invention includes a gate clock signal and a start vertical signal (hereinafter, referred to as an STS). The gate clock signal is a signal transmitted to the gate driver. The gate clock signal has the same period as the horizontal synchronization signal Hsync, and the gate-on voltage is transmitted to each of the gate lines G1 -Gn during one period of the gate clock signal. The start signal STS is a signal for outputting a gate-on voltage. The gate-on voltage is generated from a rising edge of the next gate clock signal after the start signal STS is generated.

The backlight unit 40 ′ includes a backlight unit controller 110, a column driver 112, a scan driver 114, and a display unit 116.

The display unit 116 includes a plurality of scan lines S1 -Sp for transmitting a scan signal, a plurality of column lines C1-Cq for transmitting a column signal, and a plurality of light emitting pixels EPX. Each of the plurality of light emitting pixels EPX is positioned in a region defined by the scan lines S1 -Sp and the column lines C1 -Cq intersecting the scan lines. The scan lines S1-Sp are connected to the scan driver 114, and the column lines C1 -Cq are connected to the column driver 112. The scan driver 114 and the column driver 112 are connected to the backlight unit controller 110 to operate according to the control signal of the backlight unit controller 110.

The plurality of scan lines S1 -Sp are the scan electrodes of the above-described backlight unit, the column lines C1-Cq are the data electrodes, and each light emitting pixel EPX is formed of an FEA type electron emission device.

The backlight unit controller 110 uses a plurality of image signals DAT corresponding to the plurality of liquid crystal pixels PX corresponding to one pixel EPX of the backlight unit, and the plurality of backlight units control unit 110 corresponds to one pixel EPX of the backlight unit. The highest gray level is detected among the pixels PX, the gray level of the backlight unit pixel EPX corresponding to the detected gray level is calculated, converted into digital data, and the light emission signal CLS is transmitted to the column driver 112. . The light emission signal CLS according to an exemplary embodiment of the present invention includes 6-bit or more digital data according to the gray level of the backlight unit pixel EPX. In addition, the backlight unit controller 110 generates a scan driving control signal CS using the gate control signal. The backlight unit controller 110 generates the light emission control signal CC using the data control signal CONT2 and transmits the generated light emission control signal CC to the column driver 112.

The scan driver 114 is connected to the plurality of scan lines S1-Sp, and the backlight unit pixels EPX are synchronized with the plurality of liquid crystal pixels EX corresponding to the scan unit control signals CS in accordance with the scan drive control signal CS. The scan signal is transmitted to the gate electrode to emit light.

The column driver 112 is connected to a plurality of column lines C1-Cq, and each backlight unit pixel EPX corresponds to a plurality of liquid crystals according to the emission control signal CC and the emission signal CLS. Control to emit light corresponding to the gray scale of the pixel EX. A plurality of emission data signals are generated according to the emission signal CLS and transferred to the plurality of column lines C1-Cq according to the emission control signal CC. That is, the light emitting pixel EPX is synchronized to emit light with a predetermined gray scale in accordance with the display of the image on the plurality of liquid crystal pixels EX corresponding to one backlight unit pixel EPX.

Hereinafter, an operation of the display device according to the exemplary embodiment of the present invention will be described in detail with reference to FIG. 8. The data driving signal CONT2 according to the embodiment of the present invention includes a data enable signal DE, and the data signal D1- from the data driver 104 during a period where the data enable signal DE is at a high level. Dm) is output.

8 is a diagram illustrating a data enable signal DE, a gate clock signal CPV, a gate signal G1 -Gn, a scan signal s1-s3, and a light emission enable signal LE.

As shown in FIG. 8, the gate signals G1 -Gn have a gate-on voltage for one period of the gate clock signal CPV in synchronization with the rising edge timing of the gate clock signal CPV.

The backlight unit controller 110 generates a scan driving control signal CS by recognizing the gate clock signals CPV of the plurality of liquid crystal pixels PX corresponding to each row of the backlight unit pixels EPX. That is, the backlight unit controller 110 calculates in advance a period T1 during which a plurality of gate signals corresponding to one row of the backlight unit pixels EPX are transmitted. The backlight unit controller 110 generates the first clock signal CLK that is generated in synchronization with the rising edge timing R2 of the gate signal G1 at the calculated period. At the time point R1, the start signal STS is recognized to generate a first pulse SP generated in synchronization with the start time STS. The scan driving control signal CS includes a first clock signal CLK and a first pulse SP.

Then, as shown in FIG. 8, the scan driver is a gate transferred to the liquid crystal panel assembly 10 according to the scan driving control signal CS including the first pulse SP and the first clock signal CLK. Falling edge timing F1 of the gate signal Gw of the last row corresponding to the plurality of backlight unit pixels EPX in the first row in synchronization with the signal G1, and becoming the first level VH. Is generated at a second level in synchronization with the " According to an embodiment of the present invention, the first level is a high level and the second level VL is a low level. In this manner, the scan signal s2, the scan signal s3, and the like are sequentially generated.

In addition, the backlight unit controller 110 detects a period in which the data signal is transmitted to the plurality of liquid crystal pixels PX corresponding to the backlight unit pixels EPX in a row using the data enable signal DE, and emits light. Generate the enable signal LE. That is, the liquid crystal panel assembly 10 detects a section T2 through which a data signal is transmitted to a plurality of liquid crystal pixels corresponding to a plurality of gate lines corresponding to one row of the backlight unit pixels EPX, and during that period, A light emission enable signal LE having a third level is generated. The third level according to the embodiment of the present invention is a high level.

Then, the column driver 112 transmits the light emission data signal to the column lines C1-Cq according to the light emission control signal CC including the light emission enable signal LE.

Specifically, a period during which the data signals D1-Dm are transmitted to the first row of the plurality of liquid crystal pixels EX corresponding to the plurality of backlight unit pixels EPX connected to the scan line S1 of the first row. This is the first period TD1. At this time, the data enable signal DE rises to the high level at the start point R3 of the first period TD1, and the light emitting enable signal LE rises to the third level in synchronization with this time. The data signals D1-Dm are transferred to the plurality of liquid crystal pixels positioned in the last row among the plurality of liquid crystal pixels corresponding to the backlight unit pixels EPX connected to the scan line S1 of the first row. At the time point F2, the light emission enable signal LE falls to the fourth level. Then, the plurality of light emitting data signals DL1 -DLq are transmitted to the plurality of column lines C1-Cq in synchronization with the start point R3, and are maintained at the plurality of column lines C1-Cq until the time point F2. . That is, during the period T2, the plurality of light emitting data signals are transmitted to the plurality of column lines C1-Cq so that each pixel of the plurality of backlight units emits light in accordance with the light emitting data signal. In the same manner, when the first level scan signal s2-sq is sequentially transmitted to each of the plurality of scan lines S2-Sp, the plurality of light emitting data signals DL1- to the plurality of column lines C1-Cq. DLq) is transmitted, and the pixels of the plurality of backlight units emit light.

The display device according to the exemplary embodiment of the present invention varies the voltage level of the plurality of light emitting data signals DL1 to DLq to represent a plurality of gray levels, and adjusts the level of the cathode voltage according to the gray level (PULSE AMPLITUDE MODULATE). Can be used. In addition, the present invention is not limited thereto, and the display device according to the exemplary embodiment of the present invention modulates the pulse widths of the plurality of light emitting data signals DL1 to DLq corresponding to the gray levels to express the plurality of gray levels. width modulate). When the PWM method is used, the plurality of light emitting data signals DL1-DLq have a constant voltage level and are applied to the cathode electrode for a period corresponding to the highest gray level among the plurality of liquid crystal pixels corresponding to each backlight unit pixel. In this case, the light emission signal CLS transmitted to the column driver 112 may be 6 bits of digital data, but the present invention is not limited thereto and may be 2 to 8 bits of digital data.

As described above, the backlight unit according to the third exemplary embodiment expresses the gray level of the light emitting pixel corresponding to the plurality of liquid crystal pixels while the image data of one frame is displayed, thereby improving the dynamic contrast of the screen. You can.

By the above-described configuration, the display unit 116 of the backlight unit 40 'receives the driving signal synchronized with the image signal and emits light of an appropriate intensity according to the luminance information for each pixel, and the liquid crystal panel assembly 10 To provide. Each of the light emitting pixels EPX of the backlight unit 40 'display unit 115 is preferably driven so that gray scale representation of 2 to 8 bits is possible.

As a result, when the liquid crystal panel assembly 10 displays a screen of different brightness for each position, the backlight unit 40 'provides strong light to the areas of the liquid crystal panel assembly 10 pixels that display the bright portion, Weak light may be provided to the portions of the liquid crystal panel assembly 10 pixels that display the portion. In addition, the light emitting pixels of the backlight unit 40 ′ corresponding to the pixels of the liquid crystal panel assembly 10 displaying black may be turned off.

As a result, the display device of the present embodiment can improve the dynamic contrast of the screen through the above-described process. The embodiment using a display device using a liquid crystal panel assembly has been described so far, but the present invention is not limited thereto. As a display device other than self-luminous, it is applicable to both display devices that receive images from a backlight unit and display an image.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the range of.

As described above, the display device and the driving method thereof according to the present invention can improve display quality by increasing a dynamic contrast ratio of a screen by using a display panel having a low resolution as a backlight unit. In addition, the display device and the driving method thereof according to the present invention can reduce the total power consumption by reducing the power consumption of the backlight unit, and can be easily manufactured to a large display device of 30 inches or more according to the size of the backlight unit.

Claims (17)

A plurality of first scan lines for transmitting a first scan signal, a plurality of first data lines for transferring a first data signal, and a plurality of pixel circuits defined by the first scan line and the first data line and having respective pixel circuits A panel assembly comprising a first pixel and A plurality of second scan lines for transmitting a second scan signal, a plurality of second data lines for transferring a second data signal, and a plurality of second pixels defined by the second scan line and the second data line; Including a backlight unit, The second pixel corresponds to at least two first pixels of the plurality of first pixels, and emits light corresponding to the highest gray level among the at least two first pixels. The method of claim 1, The second pixel is a field emission array type electron emission device, which includes a cathode electrode and a gate electrode, emits light by a voltage difference between the gate electrode and the cathode electrode, The second scan signal is transmitted to the gate electrode, and the second data signal is applied to the cathode electrode. The method of claim 2, The second scan signal transmitted to the second pixel corresponding to the at least two first pixels is transmitted to the second scan line during a first period in which the first scan signal corresponding to the at least two first pixels is transmitted. , And wherein the second data signal applies a second data signal corresponding to the highest gray level to the second pixel in response to a time point at which the first data signal of the at least two first pixels is applied. The method of claim 3, And when the first data signal of the at least two first pixels is applied, the second data signal is applied to the cathode as a cathode voltage for displaying the highest gray scale. The method of claim 4, wherein The backlight unit, Generating a light emission signal for displaying a gray level corresponding to the highest gray level among the at least two first pixels on the second pixel, And a cathode voltage for displaying the highest gray level corresponds to the light emission signal. The method of claim 5, And the light emitting signal is at least 6 bits of digital data. The method of claim 2, The second scan signal transmitted to the second pixel corresponding to the at least two first pixels is transmitted to the second scan line during a first period in which the first scan signal corresponding to the at least two first pixels is transmitted. , The second data signal corresponds to a point in time at which the first first data signal of the at least two first pixels is applied, and receives a constant second data signal for a period corresponding to the highest gray level of the at least two first pixels. A display device applied to the light emitting pixel. The method of claim 7, wherein The second data signal is synchronized with a point in time at which the first data signal of the at least two first pixels is applied, so that the second data signal is supplied to the second pixel as a constant cathode voltage for a period corresponding to the highest gray level. Approved display device. The method of claim 8, The backlight unit, Generating a light emission signal for displaying a gray level corresponding to the highest gray level among the at least two first pixels on the second pixel, And a period corresponding to the highest gray level is a period corresponding to the light emission signal. The method of claim 9, And the light emitting signal is at least 6 bits of digital data. A plurality of first scan lines for transmitting a first selection signal, a plurality of first data lines for delivering a first data signal, and a pixel circuit defined by the first scan line and the first data line; A panel assembly including a plurality of first pixels; A plurality of second scan lines transferring a second selection signal, a plurality of second data lines transferring a second data signal, and a plurality of second pixels defined by the second scan line and the second data line; The second pixel may include a backlight unit corresponding to at least two first pixels of the plurality of first pixels. (a) transmitting the second selection signal to a second scan line of the second pixel corresponding to the first pixels during a first period in which a first selection signal is transmitted to the at least two first pixels And (b) transmitting the second data signal to a second data line of the second pixel in response to a time point at which the first first data signal of the at least two first pixels is applied; Method of driving a display device comprising a. The method of claim 11, (c) detecting the highest gray level of the at least two first pixels More, And (b) applying the second data signal corresponding to the detected gray level to the second pixel. The method of claim 12, (d) generating a light emission signal for displaying a gray level corresponding to the highest gray level among the at least two first pixels on the second pixel; More, And the second data signal of step (b) has a voltage corresponding to the light emission signal. The method of claim 13, And the light emitting signal is at least 6 bits of digital data. The method of claim 11, (c) detecting the highest gray level of the at least two first pixels More, In the step (b), the second data signal is applied to the second pixel during the first period corresponding to the detected gray level. The method of claim 15, (d) generating a light emission signal for displaying a gray level corresponding to the highest gray level among the at least two first pixels on the second pixel; More, And the first period of step (b) corresponds to the light emission signal. The method of claim 16, And the light emitting signal is at least 6 bits of digital data.

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