Electron emission display and driving method thereof

An electron emission display includes a display panel having a first substrate on which at least one first electrode is formed, a second substrate on which a second electrode and a third electrode on which an electron emission source is formed are formed. A fourth electrode is formed between the first and second substrates to focus towards a corresponding phosphor surface area on the at least one first electrode the electrons emitted by the electron emission source towards a corresponding phosphor surface area on the at least one first electrode, the second electrode being insulated from the third electrode and crossed therewith. A scan electrode driver applies scan pulses to the second electrode. A data electrode driver applies data pulses to the third electrode. A focusing electrode driver applies focusing voltages to the fourth electrode. The focusing electrode driver applies different voltages according to image displayed states on the display panel.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2004-0005980 filed on Jan. 30, 2004 in the Korean Intellectual Property Office, the entire content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display device. More specifically, the present invention relates to an electron emission display and a driving method thereof.

2. Description of the Related Art

In general, a flat panel display (FPD) is a display device in which a wall is provided between two substrates to manufacture an airtight device, and appropriate elements are arranged in the airtight device to display desired images. The importance of the FPD has been emphasized following the development of multimedia technologies. In response to this trend, various flat type displays such as the liquid crystal display (LCD), the plasma display panel (PDP), and the field emission display (FED) have been put to practical use.

In particular, since an electron emission display uses phosphorous emission caused by electron beams in a like manner of the cathode ray tube (CRT), it has a high probability of realizing a flat-type display which maintains the excellent features of the CRT, provides no image distortion, and allows low power consumption. In particular, it satisfies view angle, high-rate response, high resolution, fineness, and slimness criteria, and accordingly, it has become the center of public attention as the next-generation display.

The above-described electron emission display uses a cold cathode rather than a hot cathode, which includes an FED, an surface conduction emitting display (SED), and an metal insulator metal (MIM) display.

FIG. 1shows a cross-sectional view of an electron emission display. As shown, the electron emission display includes a rear substrate11and a front substrate12. A cathode electrode13and a gate electrode17are formed with an insulation layer16therebetween on the rear substrate11. An emitter15for emitting electrons according to the voltage applied to the cathode electrode13and the gate electrode17is formed on the cathode electrode13.

The front substrate12is formed to face the rear substrate11, and an anode electrode14for pulling the electrons output from the emitter15is formed on the front substrate12. Also, a phosphor surface19of red, green, and blue phosphors for the pulled electrons to collide with and emit light is formed on the anode electrode14.

A focusing electrode18is formed between the rear substrate11and the front substrate12, and it focuses the electrons generated by the emitter15formed on the cathode electrode13so that the electrons may reach the desired phosphor surface19. Further, a spacer20for dividing the anode electrode14and the focusing electrode18is used.

The above-configured electron emission display concentrates high fields on the emitter15to emit the electrons according to the quantum-mechanical tunnel effect, and the electrons emitted from the emitter15are accelerated by the voltage applied between the cathode electrode13(a scan electrode) and the gate electrode17(a data electrode) and collide with the phosphor surface19formed on the anode electrode14, thereby emitting the light and displaying images.

The brightness of the images displayed when the emitted electrons collide with the phosphor surface19varies according to values of input digital video signals. In more detail, the values of the digital video signals have 8-bit RGB data. That is, the values of the digital video signals cover 0 (00000000(2)) to 255 (11111111(2)). 256 gray scales are represented by the 256 values, and the brightness of colors are represented by the digital values.

However, since the DC voltage is consecutively applied to the focusing electrode18in the conventional electron emission display, part of the electrons emitted from the emitter15are not provided to the anode electrode14but rather to the focusing electrode18or the spacer20, and they charge the focusing electrode18or the spacer20. As a result, the electrons charged in the focusing electrode18or the spacer20influence the emitted electrons around the spacer20, and hence, the electron beams are bent, and the images around the spacer20and the focusing electrode18are distorted.

SUMMARY OF THE INVENTION

In accordance with the present invention to an electron emission display with less image distortion and a driving method for eliminating the electrons charged in a spacer or a focusing electrode, is provided.

In one aspect of the present invention, an electron emission display includes: a display panel having a first substrate on which at least one first electrode is formed, a second substrate on which a second electrode and a third electrode on which an electron emission source is formed are formed. A fourth electrode is formed between the first and second substrates and focuses electrons towards a corresponding phosphor surface area on the first electrode the electrons emitted by the electron emission source, the second electrode being insulated from the third electrode and crossed therewith. A scan electrode driver applies a scan pulse to the second electrode. A data electrode driver applies a data pulse to the third electrode. A focusing electrode driver applies a focusing voltage to the fourth electrode. The focusing electrode driver applies different voltages during the period in which the images are displayed on the display panel and the period in which the images are not displayed thereon.

A predetermined voltage is applied to the first electrode, and the electron emission source emits electrons towards a corresponding phosphor surface area on the first electrode corresponding to the voltage applied between the second and third electrodes to thus display images.

The focusing electrode driver maintains the voltage applied to the fourth electrode during the period in which the images are displayed on the display panel.

The focusing electrode driver applies a pulse with a voltage which is lower than the first voltage to the fourth electrode during the period in which no image is displayed on the display panel.

The focusing electrode driver applies to the fourth electrode during the period in which the images are displayed on the display panel a focusing voltage for allowing the electrons emitted by the electron emission source to reach a corresponding phosphor surface area on the first electrode. The focusing electrode driver applies a negative discharge voltage for discharging the charged charges to the fourth electrode during the period in which the images are not displayed.

In another aspect of the present invention, an electron emission display includes: a display panel having a first substrate on which at least one first electrode is formed, a second substrate on which a second electrode and a third electrode on which an electron emission source is formed are formed. A fourth electrode is formed between the first and second substrates and focuses towards a corresponding phosphor surface area on the at least one first electrode the electrons emitted by the electron emission source, the second electrode being insulated from the third electrode and crossed therewith. A scan electrode driver applies a scan pulse to the second electrode A data electrode driver applies a data pulse to the third electrode. A focusing electrode driver alternately applies a focusing voltage and a discharge voltage to the fourth electrode. A controller applies the scan pulse, the data pulse, the focusing voltage and the discharge voltage. The focusing electrode driver applies a discharge voltage to the fourth electrode during at least part of the period the scan pulse is applied to the scan electrode driver.

In still another aspect of the present invention, a method is provided for driving a display panel having a first substrate on which at least one first electrode is formed, a second substrate on which a second electrode and a third electrode on which an electron emission source is formed are formed, and a fourth electrode which is formed between the first and second substrates and focuses towards a corresponding phosphor surface area on the at least one first electrode the electrons emitted by the electron emission source, the second substrate being insulated from the second electrode and crossed therewith. The method includes: (a) applying a constant voltage to the first electrode; (b) applying a scan pulse to the second electrode; (c) applying a data pulse to the third electrode; (d) applying a focusing voltage to the fourth electrode, and (e) applying a negative discharge voltage to the fourth electrode during a period when images are not displayed.

DETAILED DESCRIPTION

Referring toFIG. 2, the electron emission display includes a display panel100for displaying images, a data electrode driver200for driving a data electrode, a scan electrode driver300for driving a scan electrode, a focusing electrode driver400, and a controller500.

The data electrode driver200supplies a data pulse to the data electrode according to data supplied states, and the scan electrode driver300sequentially supplies a scan pulse to the scan electrode.

The focusing electrode driver400controls the voltage applied to the focusing electrode. In more detail, the focusing electrode driver400applies a constant voltage during a period in which displaying is performed on the display panel100, and applies a discharge pulse for each period in which no displaying is performed thereon, thereby discharging the electrons accumulated on a spacer or a focusing electrode.

The controller500outputs a synchronization signal for controlling the data electrode driver200and the scan electrode driver300.

The data electrode driver200and the scan electrode driver300output a data pulse and a scan pulse respectively according to the synchronization signal output by the controller500.

Also, the cathode electrode is used as a scan electrode, and the gate electrode is used as a data electrode according to the exemplary embodiment. In addition, the cathode electrode may be used as a data electrode, and the gate electrode is used as a scan electrode according to another exemplary embodiment.

In an exemplary embodiment the display panel100shown inFIG. 2is formed as shown inFIG. 1, but can be also formed in other structural formats which include a focusing electrode.

FIG. 3shows a driving waveform of an electron emission display according to an exemplary embodiment of the present invention where h_sync is a synchronization signal of a single line output by the controller500, and the scan electrode driver300applies the scan pulse to the scan electrode in synchronization with h_sync.

The focusing electrode driver400maintains a constant voltage during the periods T1, T3, and T5in which the scan pulse is applied to the scan electrode of the display panel100, and applies a negative discharge pulse which is lower than the constant voltage during the periods T2and T4in which no scan pulse is applied to the scan electrode, thereby discharging the electrons accumulated on the spacer or the focusing electrode.

In more detail, the focusing electrode driver400includes a switch for receiving the signal from the controller500and switching the same, and applies a discharge pulse within a desired period when the control signal applied to the switch is synchronized with h_sync.

In this instance, a transistor such as a MOSFET can be used for the switch as a voltage switching circuit, and for example, a switching circuit with an input voltage of 3.3V to 5V and an output voltage of several tens of volts can be used.

FIG. 4shows a driving waveform of an electron emission display according to another exemplary embodiment of the present invention where v_sync is a synchronization signal output by the controller500per frame, and the data electrode driver200applies the data pulse to the data electrode in synchronization with v_sync.

The focusing electrode driver400maintains a constant voltage during the periods T1, T3, and T5in which the data pulse is applied to the data electrode of the display panel100, and applies a discharge pulse during the periods T2and T4in which no data pulse is applied to the data electrode, thereby discharging the electrons accumulated on the spacer or the focusing electrode.

In this case, the focusing electrode driver400includes a switch for receiving the signal from the controller500and switching the same, and applies a discharge pulse within a desired period when the control signal applied to the switch is synchronized with v_sync.

Accordingly, since the discharge pulse is applied for the respective blanking periods T2and T4of v_sync, the electrons accumulated on the spacer or the focusing electrode are discharged to thus suppress bending of the electron beams, and reduce the emission phenomenon of the electrons from the focusing electrode when the electrons charged in the focusing electrode exceed a predetermined level.

Further, the data pulse can be applied by a data enable signal (not illustrated) after the synchronization signal v_sync is applied. In this case, the focusing electrode driver400can apply the discharge pulse during the whole or part of the period until the data pulse is applied after the synchronization signal v_sync is applied. In a like manner, the focusing electrode driver400can apply the discharge pulse during the whole or part of the period until the scan pulse is applied after the synchronization signal h_sync is applied.