KR20070093708A - Electron emission display and driving method thereof - Google Patents

Abstract

An electron emission display device and a driving method thereof are provided to prevent non-uniformity of brightness by adjusting a voltage difference between gate and cathode electrodes corresponding to non-uniformity characteristic of a carbon nano tube. An electron emission display device includes a pixel unit(100), an image adjusting unit(400), a data driver(200) and a scan driver(300). The pixel unit includes plural pixels, which are illuminated by applying a voltage to first and second electrodes using data and scan signals. The image adjusting unit adjusts the illumination of the pixels corresponding to a voltage of the first electrode, adjusts an illumination ratio between pixels, and compensates for images. The data driver generates a data signal using the compensated images and delivers the generated data signal to the pixel unit. The scan driver generates a scan signal and delivers the generated scan signal to the pixel unit.

Description

Electronic emission display and driving method thereof

1 is a structural diagram showing an electron emission display device according to the prior art.

2 is a structural diagram showing a structure of an electron emission display device according to the present invention.

3 is a structural diagram illustrating an image adjusting unit employed in the electron emission display device of FIG. 2.

4 is a flowchart illustrating a process of generating a data signal in an electron emission display device according to the present invention.

*** Explanation of symbols on main parts of drawings ***

100: pixel portion 200: data driver

300: scan driver 400: image adjusting unit

410: video signal input conversion unit 420: voltage adjustment unit

430: First lookup table 440: Second lookup table

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron emission display device and a driving method thereof. More specifically, the electron emission display device and its driving method for adjusting white balance by varying the voltage difference between the gate and the cathode for each line of the electron emission display device are described. It is about a method.

BACKGROUND ART A thin, lightweight flat panel display is used as a display device of a portable information terminal such as a personal computer, a cellular phone, a PDA, or a monitor of various information devices. As such a flat panel display, an LCD using a liquid crystal panel, an organic light emitting display using an organic light emitting device, a PDP using a plasma panel, an electron emitting display using an electron emitting device, and the like are known.

The flat panel display can be classified into a memory driving method and a non-memory driving method in terms of structurally divided into an active matrix and a passive matrix, and a light emission principle. In general, the active matrix method has meaning with the memory driving method, and the passive matrix method has meaning with the non-memory driving method. The active matrix method and the memory driving method emit light at a period of a frame unit. The passive matrix method and the non-memory driving method emit a light at a period of a line unit.

As for the medium- and large-sized flat panel displays that are currently commercialized, TFT-LCD (Thin Film Transistor Liquid Crystal Display) is an active matrix method, and OLED, which is being developed as a new display device, is also an active method. On the other hand, as a new display element, the electro-emission display device is a passive matrix method, unlike other flat panel devices, and emits light only when a selected line among the horizontal lines is selected while sequentially selecting horizontal lines as a non-memory driving method. The line scan method is applied. That is, the driving method has a constant duty ratio.

In general, an electron emission device used in an electron emission display device includes a method using a hot cathode and a cold cathode as an electron source. The electron-emitting devices using the cold cathode are FEA (Field Emitter Array) type, SCE (Surface Conduction Emitter) type, MIM (Metal-Insulator-Metal) type, MIS (Metal-Insulator-Semiconductor) type, BSE (Ballistic) electron surface emitting) and the like are known.

The FEA type electron emitting device uses a low work function or high β function as an electron emission source, and uses electrons to emit electrons by electric field in vacuum. In addition, devices using electron emission sources for nanomaterials have been developed.

The SCE type electron emission device is a device in which an electron emission part is formed by providing a conductive thin film between two electrodes disposed to face each other on a substrate and providing a micro crack in the conductive thin film. The device utilizes a principle that electrons are emitted from the electron emission portion, which is the fine gap, by applying a voltage to an electrode to flow a current to the surface of the conductive thin film.

The MIM type and MIS type electron emission devices each form an electron emission portion composed of a metal-dielectric layer-metal (MIM) and a metal-dielectric layer-semiconductor structure, and apply a voltage between two metals or a metal and a semiconductor disposed between dielectric layers. It is a device using the principle that electrons are released as they move and accelerate from a metal having a high electron potential or from a semiconductor to a metal having a low electron potential when applied.

The BSE type electron emitting device forms an electron supply layer made of a metal or a semiconductor on an ohmic electrode by using the principle that electrons travel without scattering when the size of the semiconductor is reduced to a dimension area smaller than the average free stroke of electrons in the semiconductor. And an insulating layer and a metal thin film formed on the electron supply layer to emit electrons by applying power to the ohmic electrode and the metal thin film.

Like the CRT (Cathode-Ray Tube), the electron-emitting device operates by cathode electrode ray emission (self-light source, high efficiency, high luminance and wide luminance region, natural color and high color purity, wide viewing angle), operating speed, Due to the advantage of lighting that the operating temperature range is wide, it can be used in various fields, and active research has been made until recently.

1 is a structural diagram showing an electron emission display device according to the prior art. Referring to FIG. 1, the electron emission display device includes a pixel unit 10, a data driver 20, and a scan driver 30.

In the pixel portion 10, the pixel 10 is formed at a portion where the cathode electrodes C1, C2... Cn and the gate electrodes G1, G2 .. Gn intersect, and the pixel 10 includes an electron emitting portion. As a result, electrons emitted from the cathode at the electron emission part collide with the anode, and the phosphor emits light, thereby displaying gray levels. The gray level of the displayed image is changed according to the value of the input digital image signal. In order to adjust the gray level represented according to the value of the digital video signal, a pulse width modulation method or a pulse amplitude modulation method may be generally used.

In addition, the electron emitting unit is a carbon nanotube (hereinafter referred to as CNT) having high self-luminous efficiency.

The data driver 20 is connected to the cathode electrodes C1, C2 ... Cn to generate a data signal and transmit the data signal to the pixel unit so that the pixel unit 10 emits light corresponding to the data signal.

The scan driver 30 is connected to the gate electrodes G1, G2... Gn, generates a scan signal, and transmits the scan signal to the pixel unit 10 so that the pixel unit 10 is line-scanned in a horizontal line unit. By sequentially emitting light, the entire screen can be displayed while being driven while reducing circuit cost and power consumption.

In this case, in the case of expressing high brightness, a large amount of current flows in the pixel portion 10, which causes a large load on the pixel portion 10, and thus, power consumption of the light emitting display device is increased by receiving high power.

In the case of expressing low luminance, there is a problem that the brightness of the pixel portion 10 is lowered and the contrast ratio is lowered.

Accordingly, an object of the present invention is to solve the problems of the prior art, and an object of the present invention is to adjust a cathode electrode and an anode voltage in response to a characteristic non-uniformity of CNT, and to prevent the non-uniformity of luminance. It is to provide a driving method.

In order to achieve the object of the present invention, a first aspect of the present invention includes a pixel portion including a plurality of pixels emitting light by applying a predetermined voltage to the first electrode and the second electrode by a data signal and a scan signal, An image adjusting unit for correcting an image signal by adjusting an emission rate of the pixel in response to a voltage of a first electrode and adjusting an emission ratio of at least one pixel of the plurality of pixels to another pixel, by using the corrected image signal The present invention provides a light emitting display device including a data driver generating a data signal and transmitting the same to the pixel unit, and a scan driver generating a scan signal and transmitting the scan signal to the pixel unit.

In order to achieve the object of the present invention, a second aspect of the present invention provides a pixel unit including a plurality of pixels which emit light by applying a predetermined voltage to the first electrode and the second electrode by a data signal and a scan signal. An image adjusting unit configured to set a first correction coefficient corresponding to the voltage of the first electrode, and to set a second correction coefficient by comparing luminance of at least one pixel of the plurality of pixels with another pixel, the first correction coefficient and the first correction coefficient; And a data driver for determining a light emission time of the pixel by using a correction factor and a scan driver for generating a scan signal and transmitting the scan signal to the pixel.

In order to achieve the object of the present invention, a third aspect of the present invention provides a method of driving an electron emission display device including a pixel which generates a data signal using an image signal and emits light by the voltage of the first electrode and the second electrode. 3. The method of claim 1, wherein the entire pixel of the pixel unit receives a predetermined image signal and emits light to determine a second correction coefficient using an emission ratio between at least one pixel among the entire pixels and other pixels, wherein the first pixel unit includes: Determining a first correction coefficient corresponding to a change in the voltage of an electrode, and correcting the image signal through the first correction coefficient and the second correction coefficient to generate the data signal using the corrected image signal. The present invention provides a method of driving an electron emission display device.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

2 is a structural diagram showing a structure of an electron emission display device according to the present invention. Referring to FIG. 2, the pixel unit 100 includes a pixel driver 100, a data driver 200, a scan driver 300, and an image controller 400.

In the pixel unit 100, a plurality of cathode electrodes C1, C2... Cn are arranged in a column direction, and a plurality of gate electrodes G1, G2... Gn are arranged in a row direction, and a cathode electrode C1. Electron emission sources are provided at portions where C2..Cn and the gate electrodes G1, G2..Gn intersect to form the pixel 101. In addition, the gate electrodes G1, G2 .... Gn may be arranged in the column direction, and the cathode electrodes C1, C2 .... Cn may be arranged in the row direction. In the following description, it is assumed that the cathode electrodes C1, C2 .... Cn are arranged in the column direction and the gate electrodes G1, G2 .... Gn are arranged in the row direction.

The data driver 200 is connected to the cathode electrodes C1, C2... Cn and transmits a data signal to the cathode electrodes C1, C2... Cn. The data driver 200 may turn ON / OFF the pixel 101 formed at a portion where the selected cathode electrodes C1, C2 .... Cn and the gate electrodes G1, G2 .... Gn intersect. To generate an electrode signal.

The scan driver 300 is connected to the gate electrodes G1, G2 ... Gn, and selects one gate electrode G1, G2 ... Gn from among the plurality of gate electrodes arranged in the row direction. The data signal is transmitted to the pixel 101 connected to the electrodes G1, G2 .... Gn.

The image controller 400 corrects the unevenness of the luminance caused by the variation of the voltages of the gate electrode and the cathode electrode corresponding to the luminance change according to the lifespan of the pixels and the light emission deviation between the pixels to express the image with uniform luminance. .

3 is a structural diagram illustrating an image adjusting unit employed in the electron emission display device of FIG. 2. Referring to FIG. 3, the image controller 400 includes an image signal input converter 410, a voltage adjuster 420, a first lookup table 430, and a second lookup table 440.

The video signal input converter 410 is a means for receiving a video signal, correcting the output signal, and outputting a corrected video signal. A first correction coefficient is received and a second correction coefficient for luminance deviation between pixels is received from the second lookup table 440 to correct the image signal by using the first correction factor and the second correction coefficient. The image signal is expressed as a digital signal, and the image signal input converter 410 corrects the input image signal and transmits it to the data driver 200.

The first correction coefficient is used to adjust the deviation in which the luminance of the pixel is changed in response to the change in the voltage of the cathode electrode and the gate electrode, and the second correction coefficient is the luminance of each pixel with respect to the voltage of the same cathode electrode and the gate electrode. This is to prevent the non-uniformity of.

The voltage adjusting unit 420 adjusts the voltage of the gate electrode in order to prevent the luminance from dropping according to the lifetime of the electron emission source so that the difference between the voltage of the gate electrode and the voltage of the cathode electrode is varied. The voltage adjusting unit 420 transfers the voltage adjusting signal corresponding to the changed gate voltage to the first lookup table 430.

The first lookup table 430 stores a first correction coefficient corresponding to each voltage of the gate electrode, receives a voltage adjustment signal from the voltage adjusting unit 420, and selects a first correction coefficient corresponding to the voltage adjustment signal to display an image. The signal input converter 410 is transferred. Therefore, the electron emission source gradually lowers the luminous efficiency in response to the lifetime, so that when the voltage of the gate electrode is changed, the electron emission source transmits a first correction coefficient corresponding to the changed gate electrode voltage to the image signal input converter 410. do.

The second lookup table 440 transfers a data signal having a predetermined gray scale value to all pixels in order to prevent luminance unevenness due to light emission deviations between the pixels, thereby selecting a specific pixel among the pixels. Select and store a second correction coefficient such that another pixel is corrected to the brightness of the selected specific pixel. The number of second correction coefficients is set to the same number as the number of pixels in the pixel portion, and one pixel has one second correction coefficient. The selected pixel calculates a second correction coefficient based on the pixel which emits the darkest light when a data signal having a predetermined gray scale value is received.

4 is a flowchart illustrating a process of generating a data signal in an electron emission display device according to the present invention. Referring to Figure 4,

First Step (ST100): A predetermined data signal is transmitted to the pixel unit 100 so that all pixels 101 of the pixel unit 100 receive the same gray scale value and emit light. In this case, each pixel has a characteristic difference, and thus luminance is expressed differently, resulting in uneven luminance.

Second Step ST110: Select one pixel among all the pixels of the pixel unit 100 to generate a second correction coefficient by comparing the luminance ratio of each of the selected one pixel and all other pixels. The number of second correction coefficients is equal to the number of all pixels of the pixel unit 100 by comparing one selected pixel with one selected pixel. In this case, the selected pixel is preferably selected as the darkest light emitting pixel among the light emitting pixels. The second correction coefficient is stored in the second lookup table 440.

Third Step ST120: The gate voltage of the pixel unit 100 is varied to grasp the change in luminance of the pixel according to the gate voltage, and select a first correction coefficient according to the change in luminance. After calculating one correction coefficient by selecting one pixel, the calculated first correction coefficient may be applied to other pixels, and selecting a plurality of pixels to calculate the first correction coefficient, respectively, to calculate the first correction coefficient. The correction factor can be applied. The first correction coefficient is measured in advance and stored in the first lookup table 430, and selects the first correction coefficient stored in the first lookup table 430 according to the adjustment of the gate voltage.

Fourth Step ST130: Generates a data signal using the first correction factor and the second correction factor, and adjusts the time at which the pixel 101 emits light according to the data signal, thereby graying out the time at which the pixel 101 emits light. To be represented.

While preferred embodiments of the present invention have been described using specific terms, such descriptions are for illustrative purposes only and it is understood that various changes and modifications may be made without departing from the spirit and scope of the following claims. You must lose.

According to the electron emission display device and the driving method thereof according to the present invention, it is possible to prevent the unevenness of the luminance due to the characteristic difference of each pixel and to prevent the unevenness of the luminance due to the change of the voltage difference between the gate electrode and the cathode electrode.

Claims (16)

A pixel unit including a plurality of pixels which emit light by applying a predetermined voltage to the first electrode and the second electrode by the data signal and the scan signal; An image adjusting unit configured to adjust an emission rate of the pixel in response to a voltage of the first electrode and to correct an image signal by adjusting an emission ratio of at least one pixel among the plurality of pixels and another pixel; A data driver which generates a data signal using the corrected video signal and transmits the data signal to the pixel unit; And And a scan driver for generating a scan signal and transmitting the scan signal to the pixel unit. The method of claim 1, The image adjusting unit, A first lookup table for storing a first correction coefficient corresponding to a change in the voltage of the first electrode; A second lookup table for storing a second correction coefficient corresponding to a predetermined video signal for each pixel; And An image signal input unit configured to correct the image signal using the first correction coefficient and the second correction coefficient; And a voltage adjustor configured to adjust the voltage of the first electrode and transmit a voltage control signal corresponding to the voltage of the first electrode to the first lookup table. The method of claim 2, And the first lookup table stores at least two first correction coefficients corresponding to the voltage control signal and adjusts the emission rate by the first correction coefficient. The method of claim 2, And the first correction coefficient is formed by a ratio of the luminance according to the first voltage of the first electrode and the luminance according to the second voltage of the first electrode. The method of claim 2, The second lookup table is An electron emission display device having a size of the total number of pixels of the pixel portion and storing the second correction coefficient corresponding to each pixel. The method of claim 2, And the second correction coefficient is formed by using the light emission ratio between at least one pixel of the whole pixels and another pixel when all pixels of the pixel part receive the same gray level signal and emit light. The method of claim 1, And the data driver expresses the gray scale by adjusting the emission time of the pixel through the first and second correction coefficients. A pixel unit including a plurality of pixels which emit light by applying a predetermined voltage to the first electrode and the second electrode by the data signal and the scan signal; An image adjusting unit configured to set a first correction coefficient corresponding to the voltage of the first electrode, and set a second correction coefficient by comparing luminance of at least one pixel of the plurality of pixels with another pixel; A data driver configured to determine a light emission time of the pixel through the first correction factor and the second correction factor to express gray scales; And And a scan driver for generating a scan signal and transmitting the scan signal to the pixel unit. The method of claim 8, The image adjusting unit, And a second lookup table for storing the first correction coefficient and a second lookup table for storing the second correction coefficient. The method of claim 9, And the image adjuster further includes a voltage adjuster for detecting a voltage of the first electrode and transferring the detected voltage to the first lookup table. A method of driving an electron emission display device comprising a pixel generating a data signal using an image signal and emitting light by voltages of a first electrode and a second electrode, Obtaining a second correction coefficient using an emission ratio between at least one pixel of the entire pixels and other pixels by receiving a predetermined image signal by all pixels of the pixel unit; Determining a first correction coefficient corresponding to a change in the voltage of the first electrode of the pixel unit; And And correcting the image signal through the first correction coefficient and the second correction coefficient to generate the data signal using the corrected image signal. The method of claim 11, And a light emission time of the pixel controlled by the first correction coefficient and the second correction coefficient to express the gray scale by the light emission time. The method of claim 11, And the first correction factor and the second correction factor are respectively determined using a lookup table. The method of claim 11, And the first correction coefficient is formed by a ratio of the luminance according to the first voltage of the first electrode and the luminance according to the second voltage of the first electrode. The method of claim 11, And the first correction coefficient is updated after the emission ratio is measured. The method of claim 11, The second correction coefficient is a driving method of an electron emission display device which is formed by using the light emission ratio between at least one pixel of the whole pixels and another pixel when all pixels of the pixel part receive the same gray level signal. .

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