KR20080087503A - Electron emission display device and control method thereof - Google Patents

Abstract

A light emitting display device and a controlling method thereof are provided to enhance image quality by increasing luminance on pixels having lower luminance than a reference luminance value. A light emitting display device includes a panel(100), data and scan drivers(200,300), a controller(500), and an image signal compensator(600). The panel includes plural pixels. The data driver applies a data signal to the panel. The scan driver applies a scan signal to the panel. The controller outputs image, data driving control, and scan driving control signals. The image signal compensator compensates for the image signals in order to measure luminance distribution or current on each pixel based on a maximum value of a data signal applied to the pixels, decrease luminance of the pixels higher than a reference luminance, and increase the luminance of the pixels lower than the reference luminance.

Description

ELECTRONIC EMISSION DISPLAY DEVICE AND CONTROL METHOD THEREOF

1 is a block diagram illustrating an electron emission display device according to an exemplary embodiment of the present invention.

FIG. 2 is a cross-sectional view of a specific area of the panel employed in the electron emission display element shown in FIG. 1. FIG.

3 is a block diagram illustrating a configuration of an image signal correction unit illustrated in FIG. 1.

4A to 4C are graphs illustrating a transfer function applied to the image signal correcting unit shown in FIG. 3.

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

100: panel 110: pixel

200: data driver 300: scan driver

400: power supply unit 500: control unit

600: image signal correction unit 610: measurement unit

620: memory 630: correction unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron emission display device. More particularly, the present invention relates to an electron emission display device and a method of controlling the same, which improves the image quality by preventing luminance unevenness between pixels.

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. Such flat panel displays include LCDs using liquid crystal panels, organic light emitting displays using organic light emitting diodes, and PDPs using plasma panels.

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 device, an electro-emission display device is a passive matrix method and, unlike other flat panel devices, is a non-memory driving method that sequentially emits a horizontal line while emitting light only when the selected line is selected. The line scan method is applied. That is, the driving method has a constant duty ratio.

Such an electron emission display device includes an electron emission device for each pixel, and the electron emission device emits electrons from the cathode electrode in response to a voltage between the cathode electrode and the gate electrode. It is a device that is accelerated by the anode electrode and collides with a phosphor to operate in a manner of emitting light.

In general, the electron-emitting device has a method using a hot cathode and a cold cathode as an electron source, the electron emitting device using a cold cathode, 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) type and the like are known.

The FEA type electron emitting device uses a material having a low work function or high β function as an electron emission source and uses electrons to be emitted by an electric field difference in vacuum. Devices that apply electron emission sources to materials or nanomaterials have been developed.

In addition, 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.

Also. The MIM and MIS electron emission devices each form an electron emission portion formed of a metal-dielectric layer-metal (MIM) and a metal-dielectric layer-semiconductor (MIS) structure, and are disposed between two metals or metals and semiconductors having a dielectric layer interposed therebetween. When a voltage is applied to the device, a device using the principle of emitting electrons while moving and accelerating from a metal having a high electron potential or a metal having a low electron potential toward the metal.

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 region 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.

In the conventional electron emission display device, an electron emission unit is provided in each pixel provided in the pixel unit, and the luminance of the pixel is determined by the amount of electrons emitted by the electron emission unit. In the manufacturing process of the electron emitting unit, even if the same image signal is input due to unevenness of each of the electron emitting units, there is a problem in that the amount of electrons is emitted and thus the luminance of each pixel is different.

According to the present invention, in correcting luminance non-uniformity between pixels due to non-uniformity of the electron emission unit, an electron-emitting display device for improving the quality of an image by enhancing luminance so as to correspond to a reference luminance value even for a pixel having a luminance lower than the reference luminance value And the control method thereof.

An electron emission display device according to an exemplary embodiment of the present invention includes a panel including a plurality of pixels; A data driver for applying a data signal to the panel; A scan driver for applying a scan signal to the panel; A control unit which outputs an image signal, a data drive control signal and a scan drive control signal; The luminance distribution or current of each pixel is measured with respect to the maximum value of the data signal applied to each pixel, and lowered for a pixel having a luminance higher than the reference luminance value by using a preset reference luminance value, and the reference luminance. A pixel having a luminance lower than the value may include an image signal correcting unit configured to correct the image signal so as to increase it.

The image signal corrector may include: a luminance / current measuring unit configured to measure luminance or current of each pixel included in the panel; A memory in which the reference luminance value is stored; And a correction unit configured to correct an image signal input to correspond to the reference luminance value.

In this case, the correction unit corrects an image signal corresponding to each pixel by using the first to third transfer functions.

In addition, the first transfer function has a slope corresponding to a ratio of an input signal to an output signal of less than 1, and is applied to a pixel having a luminance higher than a reference luminance value to correct an image signal applied to the pixel. The second transfer function has a slope corresponding to a ratio of an input signal to an output signal greater than 1, and is applied to a pixel having a luminance lower than a reference luminance value to correct an image signal applied to the pixel, and to transmit the second transfer function. The function is characterized by clipping at high gradations.

In addition, the method of controlling an electron emission device according to an embodiment of the present invention includes the steps of measuring the luminance or current of each pixel provided in the panel; Comparing the measured value with a preset reference luminance value; And correcting the image signal so as to lower the value of the pixel having a luminance higher than the reference luminance value and increase the value of the pixel having the luminance lower than the reference luminance value by using the preset reference luminance value. do.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram illustrating an electron emission display device according to an exemplary embodiment of the present invention.

As shown in FIG. 1, an electron emission display device according to an exemplary embodiment of the present invention includes a panel 100 including a plurality of pixels 110, a data driver 200, a scan driver 300, and a power supply unit ( 400 and the control unit 500, and further includes an image signal correction unit 600 for correcting the image signal provided from the control unit in order to overcome luminance unevenness of each pixel.

That is, the electron emission display device according to the present invention measures the luminance distribution or the current for each pixel with respect to the maximum value of the data signal applied to each pixel in order to improve the uniformity of the luminance, and sets a predetermined reference luminance value (one For example, by using the luminance average value of the entire screen), the image signal is adjusted so as to lower it for pixels having a luminance higher than the reference luminance value and to raise it for pixels having a luminance lower than the reference luminance value. .

In this case, the luminance uniformity of the screen of the electron emission display device is adjusted by calculating a correction coefficient using the reference luminance value and adjusting the image signal value so that the correction coefficient lowers the luminance for the individual pixel having the luminance higher than the reference luminance value. Although there is a method of improving the, the uniformity is compensated for in this way, there is a disadvantage that the compensation is not performed for the pixel lower than the reference luminance value.

Accordingly, an embodiment of the present invention aims to improve image quality by improving luminance so as to correspond to a reference luminance value even for a pixel having a luminance lower than the reference luminance value.

Referring to FIG. 1, the panel 100 includes a plurality of pixels 110, and each of the plurality of pixels includes an electron emission device (not shown).

In addition, the panel 100 includes n scan lines S1, S2,... Sn, m data lines D1, D2, ... Dm, and an anode electrode, and the scan lines S1, S2, ... Sn) and the data lines D1, D2, ... Dm are formed to cross each other.

The anode electrode may be formed over the entire area of the panel. However, this may be formed in the form of a plurality of stripes formed in a row direction similar to the scan lines, or may be formed in the form of a plurality of stripes formed in a column direction similar to the data lines, or may be formed in a mesh form.

Even when the anode electrode is formed in the form of a plurality of stripes or in the form of a mesh, the same voltage is generally applied to the entire anode electrode.

In addition, the pixel includes a cathode electrode, a gate electrode, and an anode electrode, and is formed in an area where the scan line and the data line cross each other.

In this case, any one of the scan line and the data line serves as the cathode electrode, and the other one of the scan line and the data line serves as the gate electrode.

The data driver 200 generates a data signal corresponding to the image signal corrected by the image signal corrector and applies the data signal to the data lines D1, D2, ... Dm.

In the present invention, a pulse width modulation (PWM) type data driver will be described. However, any data driver for adjusting the electron emission period of the electron emission device 110 in response to the input image data will be described. Included in the category.

In addition, the scan driver 300 sequentially applies a scan signal to the scan lines S1, S2,... Sn.

Preferably, the power supply unit 400 is configured of a switching mode power supply (SMPS), and a first power source VS1 and a second power source VS2 are respectively provided to the data driver 200, the scan driver 300, and the anode electrode. ) And a third power supply VS3.

The controller 500 outputs an image signal, a data driving control signal, and a scan driving control signal, and the data driver and the scan driver receive the image signal and the control signal and apply the data signal and the scan signal to each pixel. Play a role.

However, in the exemplary embodiment of the present invention, the image signal output from the controller 500 is corrected by the image signal corrector 600 so as to correspond to a reference luminance value according to whether luminance of each pixel is uniform and the data driver 200 Characterized in that delivered to.

That is, the image signal correction unit 600 measures a luminance distribution or current for each pixel with respect to the maximum value of the data signal applied to each pixel, and sets a predetermined reference luminance value (for example, the luminance average value of the entire screen). By lowering the pixel for a pixel having a luminance higher than the reference luminance value, and correcting the image signal so as to increase it for a pixel having a luminance lower than the reference luminance value, to provide the corrected image signal to the data driver Play a role.

At this time, for the image signal input to the pixel having a luminance lower than the existing luminance value, the image signal is corrected by using a transfer function whose slope is greater than 1 and clipping at a high gradation portion as its correction coefficient. It features.

That is, the image signal is corrected by using a transfer function for decreasing the luminance for pixels brighter than the reference luminance value and using a transfer function for increasing the luminance for pixels darker than the reference luminance value.

In addition, the transfer function for compensating for the dark pixel is clipped at the high gray level to compensate for the sub-gradation below which the video signal is widely distributed.

In this case, gray level expression may become difficult when the input signal in which clipping occurs is difficult, but since most of the image signals exhibit a lower gray level than the input signal, the gray level can be compensated normally.

Accordingly, in the embodiment of the present invention, the luminance may be improved to correspond to the reference luminance value even for a pixel having a luminance lower than the reference luminance value in correcting the luminance non-uniformity due to the non-uniformity of the electron emission unit.

FIG. 2 is a cross-sectional view of a specific area of a panel employed in the electron emission display device illustrated in FIG. 1.

That is, this is a cross-sectional view of each pixel provided in the panel, but this is only one embodiment, and the present invention is not limited to the pixel structure shown in FIG.

Referring to FIG. 2, the panel includes an electron emission substrate 120 and an image forming substrate 130. In addition, the electronic device may further include a spacer 140 that maintains a constant gap between the electron emission substrate 120 and the image forming substrate 130.

The electron emission substrate 120 is a substrate that emits electrons in response to the voltage between the cathode electrode 122 and the gate electrode 124. The back substrate 121, the cathode electrode 122, the insulating layer 123, and the gate are provided. The electrode 124 and the electron emission part 125 are provided.

The back substrate 121 may be, for example, a glass or silicon substrate. When the back substrate 121 is formed by back exposure using a carbon nanotube (CNT) paste as the electron emission unit 125, a transparent substrate such as a glass substrate may be formed. desirable.

The cathode electrode 122 may be formed in a stripe shape on the rear substrate. The cathode electrode 122 is supplied with a data signal or a scan signal applied from the data driver or the scan driver. Accordingly, the cathode electrode 122 may be a conductor, and for the same reason as the back substrate 121, may be a transparent conductor such as indium tin oxide (ITO).

The insulating layer 123 is formed on the back substrate 121 and the cathode electrode 122, and electrically insulates the cathode electrode 122 from the gate electrode 124. The insulating layer 123 may be made of an insulating material, for example, PbO and SiO ₂ mixed glass.

The gate electrode 124 is disposed on the insulating layer 123 in a predetermined shape, for example, in a direction crossing the cathode electrode 122 on a stripe, and each data signal or scan signal applied from the data driver or the scan driver. Is supplied. The gate electrode 124 is made of a metal having good conductivity, such as at least one conductive metal material selected from gold (Au), silver (Ag), platinum (Pt), aluminum (Al), chromium (Cr), and alloys thereof. Can be. The insulating layer 123 and the gate electrode 124 have at least one first opening 126 at the intersection of the cathode electrode 122 and the gate electrode 124 so that the cathode electrode 122 is exposed.

The electron emission unit 125 is electrically connected to and positioned on the cathode electrode 122 exposed by the first opening 126, and includes a carbon nanotube; Nanotubes by graphite, diamond, diamond-like carbon or a combination thereof; Or a nanowire of Si or SiC.

The image forming substrate 130 is a substrate for forming an image by electrons emitted from the electron emission substrate 120 colliding with each other to form an image. The front substrate 131, the anode electrode 132, the phosphor 133, and the light shielding film 134 and a metal reflective film 135.

The front substrate 131 is preferably made of a transparent material such as glass so that light emitted from the phosphor 133 is transmitted to the outside.

The anode electrode 132 is preferably made of a transparent material such as an ITO electrode so that light emitted from the phosphor 133 is transmitted to the outside. The anode electrode 132 accelerates the electrons emitted from the electron emitting device even better. To this end, a high voltage positive voltage is applied to the anode electrode 132 to accelerate the electrons toward the phosphor 133.

The phosphor 133 emits light due to the collision of electrons emitted from the electron emission substrate 120, and is selectively disposed on the anode electrode 132 at random intervals. Examples of the G phosphor, that is, the phosphor that develops green color include, for example, ZnS: Cu, Zn ₂ SiO ₄ : Mn, ZnS: Cu + Zn ₂ SiO ₄ : Mn, Gd ₂ O ₂ S: Tb, Y ₃ Al ₅ O ₁₂ : Ce, ZnS: Cu, Al, Y ₂ O ₂ S: Tb, ZnO: Zn, ZnS: Cu, Al + In ₂ O ₃ , LaPO ₄ : Ce, Tb, BaO ㅇ 6Al ₂ O ₃ : Mn, (Zn, Cd) S: Ag, (Zn, Cd) S: Cu, Al, ZnS: Cu, Au, Al, Y ₃ (Al, Ga) ₂ O ₁₂ : Tb, Y ₂ SiO ₅ : Tb, or LaOCl: Tb Can be used. In addition, the B phosphor, i.e., a phosphor that develops blue color, may be, for example, ZnS: Ag, ZnS: Ag, Al, ZnS: Ag, Ga, Al, ZnS: Ag, Cu, Ga, Cl, ZnS: Ag + In ₂ O. ₃ , Ca ₂ B ₅ O ₉ Cl: Eu ²⁺ , (Sr, Ca, Ba, Mg) ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu ²⁺ , Sr ₁₀ (PO ₄ ) ₆ C ₂ : Eu ²⁺ , BaMgAl ₁₆ O ₂₆ : Eu ²⁺ , CoO, Al ₂ O ₃ Added ZnS: Ag, ZnS: Ag or Ga may be used. Further, the R phosphor, i.e., the phosphor emitting red color, may be, for example, Y ₂ O ₂ S: Eu, Zn ₃ (PO ₄ ) ₂ : Mn, Y ₂ O ₃ : Eu, YVO ₄ : Eu, (Y, Gd) BO ₃ : Eu, γ-Zn ₃ (PO ₄ ) ₂ : Mn, (ZnCd) S: Ag, (ZnCd) S: Ag + In ₂ O ₃ , or Fe ₂ O ₃ added Y ₂ O ₂ S: Eu Can be used.

The light shielding film 134 is disposed at random intervals between the phosphors 133 to absorb and block external light and prevent optical crosstalk, thereby improving contrast ratio.

The metal reflective film is formed on the phosphor 133 to better focus electrons emitted from the electron emission substrate 120, and reflects light emitted from the phosphor 133 to the front substrate 131 by collision of electrons. To improve reflection efficiency. On the other hand, if the metal reflecting film serves as an anode electrode, the formation of the anode electrode 132 is optional and may be an unnecessary component.

3 is a block diagram illustrating a configuration of an image signal correction unit illustrated in FIG. 1, and FIGS. 4A to 4C are graphs illustrating a transfer function applied to the image signal correction unit illustrated in FIG. 3.

As illustrated in FIG. 3, the image signal corrector 600 includes a luminance / current measurer 610 for measuring luminance or current of each pixel included in the panel 100; A memory 620 in which a reference luminance value is stored; And a correction unit 630 for correcting the input image signal so as to correspond to the reference luminance value. The correction unit 630 includes a correction unit 630 that corrects the input image signal according to the luminance uniformity of each pixel with respect to the image signal output from the control unit 500. It corrects the image signal so as to correspond to and transmits it to the data driver 200.

First, the luminance / current measuring unit 610 measures a luminance distribution or current for each pixel with respect to the maximum value of the data signal applied to each pixel provided in the panel 100.

As mentioned above, each of the pixels includes an electron emission unit, and the luminance of the pixel is determined by the amount of electrons emitted by the electron emission unit. In the manufacturing process of the electron emission unit, each electron emission unit Even if the same video signal is input due to nonuniformity, there is a difference in the amount of electrons emitted and the luminance of each pixel is different.

Accordingly, the luminance / current measuring unit 610 measures the luminance distribution or current for each pixel whose luminance is different due to the nonuniformity of the electron emission unit. In this case, however, it is preferable that the maximum value of the data signal is collectively applied to each pixel.

As such, when the luminance distribution or the current of each pixel is measured, the pixel having a luminance higher than the reference luminance value is lowered through the correction unit 630 by using the reference luminance value pre-stored in the memory 620. For a pixel having a luminance lower than the reference luminance value, the image signal is corrected so as to increase it, and the corrected image signal is provided to the data driver.

In this case, the reference luminance value is preferably an average value of luminance of the entire screen when the maximum value of the data signal is collectively applied, but is not necessarily limited thereto.

In addition, the correction unit corrects an image signal corresponding to each pixel by using the transfer function illustrated in FIGS. 4A to 4C.

That is, for a pixel having a luminance higher than the reference luminance value, the image signal applied to the pixel is corrected by applying a transfer function having a slope less than 1 shown in FIG. 4A, and for a pixel having a luminance lower than the reference luminance value. The image signal applied to the pixel is corrected by applying a transfer function having a slope greater than 1 to provide the corrected image signal to the data driver.

In addition, by applying a transfer function having a slope of 1 to the pixel having the same luminance as the reference luminance value, the same image signal as that of the image signal output from the controller is provided to the data driver.

However, as shown in FIG. 4C, for a video signal input to a pixel having a lower luminance than the existing luminance value, a transfer function that has a slope greater than 1 and is clipped at a high gray level is used as the correction coefficient. And correcting the video signal.

In other words, the transfer function for compensating for the dark pixels is clipped at the high gradation portion to compensate for the sub-gradation below which the image signal is widely distributed.

In this case, gray level expression may become difficult when the input signal in which clipping occurs is difficult, but since most of the image signals exhibit a lower gray level than the input signal, the gray level can be compensated normally.

The electron emission display device according to the embodiment of the present invention described above with reference to FIGS. 1 to 4 is not limited to the above-described embodiment and the accompanying drawings, and various substitutions may be made without departing from the spirit of the present invention. It will be apparent to those skilled in the art that modifications and variations are possible.

That is, as an example, it is apparent to those skilled in the art that the electron emission display device may be used as a backlight unit provided in a light receiving display device such as a liquid crystal display device.

According to the present invention, in correcting the luminance non-uniformity between pixels due to the non-uniformity of the electron emission unit, the luminance of the image can be improved by improving the luminance so as to correspond to the reference luminance value even for a pixel having a luminance lower than the reference luminance value. There is an advantage.

Claims (10)

A panel provided with a plurality of pixels; A data driver for applying a data signal to the panel; A scan driver for applying a scan signal to the panel; A control unit which outputs an image signal, a data drive control signal and a scan drive control signal; The luminance distribution or current of each pixel is measured with respect to the maximum value of the data signal applied to each pixel, and lowered for a pixel having a luminance higher than the reference luminance value by using a preset reference luminance value, and the reference luminance. And an image signal correction unit for correcting the image signal so that the pixel having a luminance lower than the value can be increased. The method of claim 1, The image signal correction unit, A luminance / current measuring unit measuring luminance or current of each pixel provided in the panel; A memory in which the reference luminance value is stored; And a correction unit for correcting an input image signal to correspond to the reference luminance value. The method of claim 2, And the correction unit corrects an image signal corresponding to each pixel by using first to third transfer functions. The method of claim 3, wherein The first transfer function has a slope corresponding to a ratio of an input signal to an output signal of less than 1, and is applied to a pixel having a luminance higher than a reference luminance value to correct an image signal applied to the pixel. Electron emission display device. The method of claim 3, wherein The second transfer function has a slope corresponding to a ratio of an input signal to an output signal greater than 1, and is applied to a pixel having a luminance lower than a reference luminance value to correct an image signal applied to the pixel. Electron emission display device. The method of claim 4, wherein And the second transfer function is clipped at a high gradation portion. Measuring luminance or current of each pixel provided in the panel; Comparing the measured value with a preset reference luminance value; And correcting the image signal so as to lower the value of the pixel having a luminance higher than the reference luminance value and increase the value of the pixel having the luminance lower than the reference luminance value by using the preset reference luminance value. A control method of an electron emission display device. The method of claim 7, wherein An electron emission display device for correcting an image signal applied to the pixel by applying a transfer function having a slope corresponding to a ratio of an input signal to an output signal of less than 1 for a pixel having a luminance higher than the reference luminance value. Control method. The method of claim 7, wherein An electron emission display device for correcting an image signal applied to the pixel by applying a transfer function having a slope corresponding to a ratio of an input signal to an output signal greater than 1 for a pixel having a luminance lower than the reference luminance value. Control method. The method of claim 9, And a transfer function having a slope greater than 1 is clipped at a high gradation portion.

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