KR20050052229A - Field emission display and deriving me thod thereof - Google Patents

Abstract

The present invention provides a field emission display device and a driving method thereof which can prevent distortion of a driving waveform while reducing the internal pressure of the scanning driver.

A driving method of a field emission display device according to the present invention includes a field emission display device including a first substrate on which at least one positive electrode is formed, a plurality of first electrodes, and a rear substrate on which a plurality of second electrodes are provided. In the present invention, a first positive voltage is sequentially supplied to the plurality of first electrodes, while a second negative voltage is applied to the second electrodes. Here, the voltage difference between the first voltage and the second voltage is a voltage for emitting electrons from the electron emission source.

The emission voltage can be increased while the scan voltage can be lowered, thereby reducing the effects of signal distortion and reducing back light emission. In addition, since the offset voltage is applied using the voltage level shift, the burden on power consumption and breakdown voltage characteristics of the driving unit can be significantly reduced.

Description

Field emission display device and driving method thereof Field Emission Display and deriving me thod

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field emission display (FED), and more particularly, to a field emission display device for adjusting luminance by converting a luminance level of an input video signal.

In general, a flat panel display (FPD) is a device for manufacturing a sealed container by standing a sidewall between two substrates, and placing a suitable material inside the container to display a desired screen. Its importance is growing with it. In response to this, various flat panel displays such as liquid crystal displays (LCDs), plasma display panels (PDPs), and field emission display devices (FEDs) have been developed and put into practical use.

In particular, the field emission display device can be realized as a flat panel display having low power consumption without distorting the image while maintaining excellent characteristics of the cathode ray tube (CRT) by using phosphor emission by electron beams in the same way as the cathode ray tube (CRT). In addition, it is attracting attention as a next-generation display because of its high view angle, high-speed response, high brightness, high definition, and thinness.

Specifically, the field emission display device has a structure of a triode having a cathode, an anode, and a gate electrode. Field emission displays having three electrodes include a normal type and an under-gate type.

In the general field emission display device, a cathode electrode, which is generally used for scanning, is formed on a rear substrate, and an insulating layer having contact holes is formed on the cathode and a gate electrode, which is generally used as a data electrode, is stacked. An emitter, which is an electron emission source, is formed in the contact hole and is connected to the cathode electrode.

In the undergate type field emission display device, a gate electrode is formed on a substrate, and an insulating layer is formed on the gate electrode. Cathode electrodes and emitters are formed on the insulating layer.

The field emission display device configured as described above concentrates a high electric field on a sharp cathode, that is, an emitter, and emits electrons by a quantum mechanical tunnel effect. Accelerated by the voltage applied to the impingement to the RGB fluorescent layer formed on both electrodes by emitting a phosphor to display an image.

As the emitted electrons collide with the fluorescent layer and the phosphor emits light, the luminance of the displayed image is changed according to the value of the input digital image signal. Specifically, the value of the digital video signal is composed of 8-bit RGB data, respectively. That is, the value of the digital video signal may be 0 (00000000 ₍₂₎ ) to 255 (11111111 ₍₂₎ ), and thus 256 grayscales may be represented by 256 values, and according to the digital value, Luminance is expressed.

In order to adjust the luminance expressed according to the value of the digital video signal, a pulse width modulation (PWM) method or an amplitude modulation (PAM) is used. .

The PWM method modulates the pulse width of the driving waveform applied to the data electrode in accordance with the digital image signal input from the data electrode driver. The PAM modulates the amplitude of the driving waveform applied to the data electrode in the data electrode driver. Pulse Amplitude Modulation (hereinafter referred to as PAM). The modulated driving waveforms are applied to the field emission display panel to display an image.

Here, the PWM method modulates the pulse width of the driving waveform applied to the data electrode according to 8-bit data of each of R, G, and B, and converts the pulse width of the digital video signal within the maximum available on-time. When 255 is input, the pulse width is maximized to display the maximum luminance. When 127 is input as the value of the digital video signal, the pulse width is 1/2 to decrease the luminance. On the other hand, in the PAM method, the pulse width is constant regardless of the input digital video signal, but the luminance is controlled by varying the pulse voltage level of the driving waveform applied to the data electrode, that is, the pulse size, according to the input digital video signal.

1 is a view illustrating waveforms applied to scan electrodes and data electrodes of a field emission display device.

In FIG. 1, when the voltage Vs is applied to the scan electrode, the display cell is turned on for the time t1 when a voltage of 0 V is applied to the data electrode, and during the time t2 when the voltage Vd is applied to the data electrode. The display cell is turned off.

In general, the field emission display device uses a voltage range of 0 to several tens of volts as the data voltage Vd to display an image. Particularly, in a general field emission display device, when a data voltage Vd corresponding to several tens of volts is used, it is sufficiently large to stably turn on and off the display cell with a sufficient driving voltage (voltage difference between the scan voltage and the data voltage). Scanning voltage Vs must be applied.

As shown in Fig. 1, assuming that the voltage Vs for sufficient emission is 120V, the output of the scan driver IC should be 120V. Therefore, the actual drive must have higher voltage characteristics. As a result, the burden on the driving unit becomes large and may cause frequent failures. In addition, the burden is even greater when a higher voltage than 120V is required.

FIG. 2 is a view showing a schematic configuration of the field emission display device. When the driving waveform applied to the time t2 of FIG. 1 is applied to the scan driver 10 and the data driver 20, the field emission display is shown. Figures showing waveforms detected at positions A, B, C, and D of the panel 30, respectively.

As shown in FIG. 2, scan waveform distortion may occur at positions of the display panel 30 that are far from the scan driver 10, that is, B and D, and the display panel far from the data driver 20. At the position 30, that is, the C and D portions, distortion of the data waveform may occur. Such distortion of the waveform may occur more severely with a higher driving voltage. In addition, the distortion of the waveform may be a factor of back emission, and the dark room contrast of the electroluminescent display may be lowered due to the back emission.

Therefore, there is an urgent need for a method of preventing distortion of the waveform while reducing the breakdown voltage with respect to the voltage of the driver.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a field emission display device and a driving method thereof capable of preventing distortion of a driving waveform while reducing the internal pressure of the scan driver.

The driving method of the field emission display device according to an aspect of the present invention for solving the above technical problem,

A driving method of a field emission display device comprising a first substrate having at least one positive electrode, a plurality of first electrodes, and a rear substrate having a plurality of second electrodes provided with an electron emission source,

Sequentially supplying a first positive voltage to the plurality of first electrodes; And

Applying a negative second voltage to the plurality of second electrodes

Including,

The voltage difference between the first voltage and the second voltage is a voltage for emitting electrons from the electron emission source.

The second electrode may be a data electrode, and the first electrode may be a scan electrode.

The second voltage may be generated by level shifting the first voltage.

In the field emission display device according to another aspect of the present invention,

A first substrate on which at least one positive electrode is formed;

A second substrate formed to cross a plurality of first electrodes and a plurality of second electrodes provided with electron emission sources;

A first electrode driver configured to apply a positive first voltage to the plurality of first electrodes; And

A second electrode driver for applying a negative second voltage to the plurality of second electrodes

Including,

The voltage difference between the first voltage and the second voltage is a voltage at which electrons are generated from the electron emission source.

The first electrode may be a scan electrode to which a first voltage is sequentially applied, and the second electrode may be a data electrode to which a second voltage is applied to supply data.

The method may further include voltage level shifting to level shift the first voltage to the second voltage.

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

3 is a diagram schematically illustrating a configuration of a field emission display device.

Referring to FIG. 3, the field emission display device includes a scan driver 84 for driving the scan lines S1 to Sm, and upper and lower data drivers 80 and 82 for driving the data lines D1 to Dn. And first to third connectors 86, 88, and 90 formed on the lower substrate 48.

The scan driver 84 sequentially supplies scan pulses to the scan lines S1 to Sm.

The upper and lower data drivers 80 and 82 supply data pulses to the data lines D1 to Dn depending on whether data is supplied or not. In this case, for example, the odd data line Dn + 1 (n is a positive integer greater than or equal to 0) receives a data pulse from the upper data driver 80, and the even data line Dn + 2 receives the lower data driver ( 82, data pulses are supplied.

The first connector 86 is electrically connected to the odd data line Dn + 1. The first connector 84 is electrically connected to the upper data driver 80. That is, the first connector 86 supplies the data pulses applied from the upper data driver 80 to the odd data line Dn + 1. The second connector 88 is electrically connected to the even data line Dn + 2. The second connector 88 is electrically connected to the lower data driver 82. That is, the second connector 88 supplies the data pulses applied from the lower data driver 82 to the even data line Dn + 2.

The third connector 90 is electrically connected to the scan lines S1 to Sm. The third connector 90 is electrically connected to the scan driver 84. That is, the third connector 90 supplies a driving signal applied from the scan driver 84 to the scan lines S1 to Sm.

4 is a waveform diagram illustrating a driving waveform applied to an electroluminescent display according to a first embodiment of the present invention.

Referring to FIG. 4, bipolar scanning pulses SP are sequentially supplied to scan lines S1 to Sm of the electroluminescent display, and synchronized with bipolar scanning pulses SP to data lines D1 to Dn. The negative data pulse DP is supplied. In the pixel cells supplied with the scan pulse SP and the data pulse DP, electrons are emitted by the voltage difference between the scan pulse SP and the data pulse DP.

For example, when a 70 V scan pulse SP is applied to the first scan line S1 and a -50 V data pulse DP is applied to the data line D, the scan pulse SP is formed on the first scan line S1. The voltage difference of 120 V is generated in the first pixel cells P1. Therefore, electrons are emitted from the first pixel cells P1 supplied with the data pulse DP.

Meanwhile, electrons are not emitted because only -50V, that is, the data pulse DP is applied to the second to mth pixel cells P2 to Pm formed in the second to mth scan lines S2 to Sm. .

Thereafter, the above process is repeated to sequentially apply the scanning pulse SP and the data pulse DP to the m th scan line Sm to drive the first to m th pixel cells P1 to Pm to display an image. do. After the image is displayed, the negative reset pulse RP is applied to the first to m th scan lines S1 to Sm. When the reset pulse RP is applied to the first to m th scan lines S1 to Sm, the charges charged in the first to m th pixel cells P1 to Pm are removed.

In order to apply a negative voltage to the data electrode, a method of shifting a voltage level of a control signal, which is generally input based on a low voltage, to a negative voltage of a desired level using a photocoupler can be used. . Alternatively, a driving circuit for generating a negative voltage may be employed.

By doing so, it is possible to reduce the load on the scan electrode driver while ensuring a sufficient driving voltage (voltage difference between the scan voltage and the data voltage).

As described above, according to the first embodiment, the burden caused by the highest voltage conventionally applied to the scan electrode can be reduced.

In addition, since it is driven at a low voltage, it is possible to reduce the influence of signal distortion that may be caused by applying a high voltage in one direction, thereby preventing the back light emission.

5 is a view showing a driving waveform applied to the field emission display device according to the second embodiment of the present invention.

Referring to FIG. 5, bipolar scanning pulses SP are sequentially supplied to scan lines S1 to Sm of the electroluminescent display, and synchronized with bipolar scanning pulses SP to data lines D1 to Dn. The negative data pulse DP is supplied. In the pixel cells supplied with the scan pulse SP and the data pulse DP, electrons are emitted by the voltage difference between the scan pulse SP and the data pulse DP.

For example, in general, when the driving voltage at which emission occurs is 50 to 60V and the driving voltage for sufficient emission is 120V, a scan pulse SP of 70V is applied to the first scan line S1 and a voltage of 20V is applied. When a data pulse DP of -50V is applied to the applied data line D, a voltage difference of 120V is generated in the first pixel cells P1 formed in the first scan line S1. Therefore, electrons are emitted from the first pixel cells P1 supplied with the data pulse DP.

Meanwhile, electrons are not emitted because only -50V, that is, the data pulse DP is applied to the second to mth pixel cells P2 to Pm formed in the second to mth scan lines S2 to Sm. .

Thereafter, the above process is repeated to sequentially apply the scanning pulse SP and the data pulse DP to the m th scan line Sm to drive the first to m th pixel cells P1 to Pm to display an image. do. After the image is displayed, the negative reset pulse RP is applied to the first to m th scan lines S1 to Sm. When the reset pulse RP is applied to the first to m th scan lines S1 to Sm, the charges charged in the first to m th pixel cells P1 to Pm are removed.

Alternatively, in general, when the driving voltage at which emission occurs is 90V and the driving voltage for sufficient emission is 110V, 70V scan pulse SP is applied to the first scan line S1 and -10V is applied. When the -40V data pulse DP is applied to the line D, a voltage difference of 120V is generated in the first pixel cells P1 formed in the first scan line S1. Therefore, electrons are emitted from the first pixel cells P1 supplied with the data pulse DP.

By doing so, it is possible to reduce the load on the scan electrode driver while ensuring a sufficient driving voltage (voltage difference between the scan voltage and the data voltage).

Although the present invention has been described above based on the preferred embodiments, the embodiments are intended to illustrate and not limit the invention. It will be apparent to those skilled in the art that various changes, modifications, and the like can be made to the embodiments without departing from the spirit of the invention. Therefore, the protection scope of the present invention will be limited only by the appended claims, and should be construed as including all changes or modifications.

According to the present invention, the voltage capable of generating electron emission can be maximized. When the internal pressure of the conventional scan driver is 100 and the data driver 80 is the maximum emission voltage, the maximum emission voltage is 100. According to the present invention, when the internal pressure of the scan driver is 100 and the data driver 80 is 80, the maximum emission voltage is 180 V. Voltage is possible.

Therefore, the emission voltage can be increased while the scan voltage can be reduced, thereby reducing the influence of signal distortion and reducing the back light emission.

In addition, since the offset voltage is applied using the voltage level shift, the burden on power consumption and breakdown voltage characteristics of the driving unit can be significantly reduced.

1 is a view illustrating waveforms applied to scan electrodes and data electrodes of a field emission display device.

FIG. 2 shows waveforms detected at each position of the field emission display panel 30 when the driving waveforms applied to the time t2 of FIG. 1 are respectively applied to the scan driver 10 and the data driver 20. Drawing.

3 is a diagram schematically illustrating a configuration of a field emission display device.

4 is a waveform diagram illustrating a driving waveform applied to an electroluminescent display according to a first embodiment of the present invention.

5 is a view showing a driving waveform applied to the field emission display device according to the second embodiment of the present invention.

Claims (8)

A driving method of a field emission display device comprising: a first substrate having at least one positive electrode; a plurality of first electrodes; and a second substrate having a plurality of second electrodes provided with electron emission sources. Sequentially supplying a first positive voltage to the plurality of first electrodes; And Applying a negative second voltage to the plurality of second electrodes Including, And the voltage difference between the first voltage and the second voltage is a voltage for emitting electrons from the electron emission source. The method of claim 1, And the second electrode is a data electrode. The method of claim 2, And the first electrode is a scan electrode. The method of claim 1, And the second voltage is generated by level shifting the first voltage. A first substrate on which at least one positive electrode is formed; A second substrate formed to cross a plurality of first electrodes and a plurality of second electrodes provided with electron emission sources; A first electrode driver configured to apply a positive first voltage to the plurality of first electrodes; And A second electrode driver for applying a negative second voltage to the plurality of second electrodes Including, And a voltage difference between the first voltage and the second voltage is a voltage at which electrons are generated from the electron emission source. The method of claim 5, And the first electrode is a scan electrode to which a first voltage is sequentially applied. The method of claim 5, And the second electrode is a data electrode to which a second voltage is applied to supply data. The method of claim 5, And a voltage level shift level shifting the first voltage to the second voltage.