KR100359020B1 - Field Emission Display - Google Patents

Abstract

The present invention relates to a field emission display device capable of removing charges accumulated on the surface of a spacer.

The field emission display device of the present invention comprises: an upper substrate; A lower substrate installed to face the upper substrate; An anode electrode installed on the upper substrate; A cathode electrode installed on the lower substrate; A spacer disposed between the upper substrate and the lower substrate to support the upper substrate and the lower substrate; A plurality of electrodes provided on the surface of the spacer; A voltage supply for supplying different voltages to the electrodes; The voltage supply unit includes a divided resistors for supplying different voltages to the electrodes, a diode respectively provided between the electrodes and the divided resistors to prevent reverse current flowing from the electrodes to the divided resistors, and between the diode and the electrodes. It is provided between the node point and the ground voltage source, and has a resistor for supplying the charge accumulated in the electrode to the ground voltage source.

Description

Field emission display device {Field Emission Display}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field emission display device, and more particularly, to a field emission display device capable of removing charges accumulated on a surface of a spacer.

Recently, various flat panel displays have been developed to reduce weight and volume, which are disadvantages of cathode ray tubes (CRTs). Such flat panel displays include liquid crystal displays (hereinafter referred to as "LCD"), field emission displays (hereinafter referred to as "FED"), and plasma display panels (hereinafter referred to as "PDP"). And electroluminescence (hereinafter referred to as "EL"). In order to improve the display quality, research and development have been actively conducted to increase the brightness, contrast and color purity of flat panel displays.

The FED concentrates a high field on a sharp cathode (emitter), emits electrons by a quantum mechanical tunnel effect, and displays an image by exciting the phosphor using the emitted electrons.

1 and 2, an FED having an upper glass substrate 2 on which an anode electrode 4 and a phosphor 6 are stacked, and a field emission array 32 formed on the lower glass substrate 8. Is shown. The field emission array 32 includes the cathode electrode 10 and the resistive layer 12 formed on the lower glass substrate 8, and the gate insulating layer 14 and the emitter 22 formed on the resistive layer 12. ) And a gate electrode 16 formed on the gate insulating layer 14. The cathode electrode 10 supplies a current to the emitter 22, and the resistive layer 12 limits the overcurrent applied from the cathode electrode 10 toward the emitter 22, thereby making it uniform to the emitter 22. It serves to supply current. The gate insulating layer 14 insulates between the cathode electrode 10 and the gate electrode 16. The gate electrode 16 is used as an extraction electrode for drawing electrons. A spacer 40 is installed between the upper glass substrate 2 and the lower glass substrate 8. The spacer 40 supports the upper glass substrate 2 and the lower glass substrate 8 so as to maintain a high vacuum state between the upper glass substrate 2 and the lower glass substrate 8.

3 is a view showing a driving device of a conventional field emission display device.

Referring to FIG. 3, a conventional driving device of a field emission display device includes a gate driver 52 connected to m gate electrode lines R to sequentially enable respective gate electrode lines R; A first cathode driver 50A which is connected to the odd-numbered cathode electrode lines C and sequentially supplies the image data to the gate electrode lines R during the period in which the gate electrode lines R are enabled; The second cathode driver 50B is connected to the first cathode electrode lines C to sequentially supply image data to the gate electrode lines R during the period in which the gate electrode lines R are enabled. Pixels 48 formed in a matrix form are positioned at the intersections of the gate electrode lines R and the cathode electrode lines C. FIG. The gate driver 52 sequentially supplies scan pulses to the first to m th gate electrodes R1 to Rm. The cathode driving units 50A and 50B are enabled when scan pulses are supplied to the gate electrodes R to supply image data to the first to nth cathode electrode lines C. Referring to FIG.

In order to display an image, a negative (-) cathode voltage is applied to the cathode electrode 10 and a positive (+) anode voltage is applied to the anode electrode 4. The gate voltage of positive polarity (+) is applied to the gate electrode 16. Then, the electron beam 30 emitted from the emitter 22 is accelerated toward the anode electrode 4. The electron beam 30 collides with the red, green, and blue phosphors 6 to excite the phosphors 6. At this time, visible light of any one of red, green, and blue colors is generated according to the phosphor 6. The spacer 40 is formed in parallel with the gate electrode 16 as shown in FIG. 4. For this reason, when the electron beam 30 generated in any one subpixel or pixel is accelerated toward the phosphor 6, the charge 42 is accumulated in the spacer 40 by the electron beam 30 diffusion. The accumulated charge 42 distorts the electric field in the panel to change the trajectory of the electron beam 30 around the spacer. In other words, the charges 42 accumulated in the spacer 40 lower the uniformity of the pixel cells or cause unevenness of the discharge, thereby degrading the image quality of the FED. In addition, when the charge 42 is accumulated at a predetermined amount or more on the surface of the spacer 40, the surface of the spacer 40 may be electrically conductive, thereby causing arcing. This arcing phenomenon not only degrades the image quality of the FED, but also destroys the emitter 22, the phosphor 6, and a driving circuit (not shown).

In order to prevent the charge 42 from accumulating in the spacer 40, a predetermined number of electrodes 46 are formed in the spacer 44 as shown in FIG. 6 in US Pat. No. 5,532,548. A predetermined voltage is applied to the electrode 46 formed in the spacer 44 to prevent charges from accumulating in the spacer 44. At this time, US Patent Publication "5,532,548" is supplied with a constant voltage to all the electrodes 46 formed in the spacer 44. However, differential voltages are applied to the spacers 44 for each height of the spacers 44 by the voltages applied to the anode electrode 4 and the cathode electrode 10. Therefore, the voltage applied to the electrodes 46 formed on the spacer 44 from the driver (not shown) and the voltage applied to the spacer 44 by the anode electrode 4 and the cathode electrode 10 are different. The electric field of is distorted and the trajectory of the electron beam 30 is converted.

Accordingly, it is an object of the present invention to provide a field emission display device capable of removing charges accumulated on the surface of a spacer.

1 is a perspective view showing a conventional field emission display device.

2 is a cross-sectional view showing a conventional field emission display device.

3 is a view showing a driving device of the field emission display device shown in FIG.

4 is a plan view showing the arrangement of the spacer shown in FIG. 1;

FIG. 5 is a cross-sectional view showing that charge is accumulated in the spacer shown in FIG. 4; FIG.

FIG. 6 is a cross-sectional view illustrating an electrode formed on the spacer illustrated in FIG. 4. FIG.

7 illustrates electrodes formed on the surface of a spacer according to an embodiment of the present invention.

8 is a circuit diagram showing in detail the voltage supply unit shown in FIG.

<Description of Symbols for Main Parts of Drawings>

2: upper glass substrate 4: anode electrode

6: phosphor 8: lower glass substrate

10 cathode electrode 12 resistive layer

14 gate insulating layer 16 gate electrode

22 emitter 30 electron beam

32: field emission array 40, 44, 60: spacer

42: charge 46,62a, 62b, 62c, 62d: electrode

48: pixel 50: cathode driver

52: gate driver 64a, 64b: side

66: voltage supply 68: power supply

70,72,74,76: Node Point

In order to achieve the above object, the field emission display device includes an upper substrate; A lower substrate installed to face the upper substrate; An anode electrode installed on the upper substrate; A cathode electrode installed on the lower substrate; A spacer disposed between the upper substrate and the lower substrate to support the upper substrate and the lower substrate; A plurality of electrodes provided on the surface of the spacer; A voltage supply for supplying different voltages to the electrodes; The voltage supply unit includes a divided resistors for supplying different voltages to the electrodes, a diode respectively provided between the electrodes and the divided resistors to prevent reverse current flowing from the electrodes to the divided resistors, and between the diode and the electrodes. It is provided between the node point and the ground voltage source, and has a resistor for supplying the charge accumulated in the electrode to the ground voltage source.

Other objects and features of the present invention in addition to the above objects will become apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 7 to 8.

7 illustrates a spacer of an FED according to an embodiment of the present invention.

Referring to FIG. 7, four thin electrodes 62a, 62b, 62c, and 62d are formed in the spacer 60 of the FED according to the embodiment of the present invention. The number of electrodes 62a, 62b, 62c, 62d formed on the surface of the spacer 60 is not limited by the embodiment of the present invention but can be arbitrarily set at the time of formation of the spacer 60. The first side face 64a of the spacer 60 is connected to the anode electrode, and the second side face 64b of the spacer 60 is connected to the cathode electrode. Electrodes 62a, 62b, 62c, and 62d formed on the surface of the spacer 60 are connected to the voltage supply 66. The voltage supply unit 66 supplies different voltages to the electrodes 62a, 62b, 62c, 62d according to the height at which the electrodes 62a, 62b, 62c, 62d are formed. The voltage values supplied to the electrodes 62a, 62b, 62c, and 62d are set equal to the voltage values induced to the electrodes 62a, 62b, 62c, and 62d by voltage values applied to the anode and cathode electrodes. do. The voltage value induced in the electrodes 62a, 62b, 62c, 62d by the voltage values applied to the anode electrode and the cathode electrode when the FED is driven is determined by Equation (1).

Vi = Vg + (Va-Vg) × (hi / h)

Where Vg is the voltage value applied to the cathode electrode, Va is the voltage value applied to the anode electrode, h is the height of the spacer 60, and hi is the height at which the electrodes 62a, 62b, 62c, 62d are formed. .) An electrode 62b is formed at a position h of 10 mm and 7 mm (hi) of the spacer 60, the cathode electrode is connected to the base voltage source Vg, and the anode electrode. Assuming that an anode voltage Va of 10 kV is applied to the electrode, a voltage of 7 kV is induced to the electrode 62b formed at a position of 7 mm of the spacer 60. At this time, the voltage supply part 66 supplies a voltage of 7 mA to the electrode 62b formed at the position of 7 mm of the spacer 60. The voltage supply unit 66 will be described in detail with reference to FIG. 8.

Referring to FIG. 8, the voltage supply unit 66 includes voltage divider resistors R1 and R2 having different resistance values so that different voltages may be applied according to the heights at which the electrodes 62a, 62b, 62c and 62d are formed. R3, R4, R5 and diodes electrically connected between the divider resistors R1, R2, R3, R4, R5 (R1 and R2, R2 and R3, R3 and R4, R4 and R5) D1, D2, D3, D4, ammeters A connected in parallel to the diodes D1, D2, D3, D4, the diodes D1, D2, D3, D4 and the ammeter A And resistors R1 ', R2', R3 ', and R4' installed between the node points 70, 72, 74, and 76 and the ground voltage source GND. The ammeters A are connected in series with the electrodes 62a, 62b, 62c, 62d provided in the spacer 60 and from the electrodes 62a, 62b, 62c, 62d through themselves to the ground voltage source GND. Measure the amount of current flowing. Diodes D1, D2, D3, and D4 prevent reverse current from flowing from the electrodes 62a, 62b, 62c, and 62d to the divided resistors R1, R2, R3, R4, and R5. The voltage induced to the electrodes 62a, 62b, 62c, and 62d formed on the spacer 60 by the voltage Va applied to the anode electrode and the voltage Vg applied to the cathode electrode is determined by Equation 1. do. The resistance values of the divider resistors R1, R2, R3, R4, and R5 are between the divider resistors R1, R2, R3, R4, and R5 (R1 and R2, R2 and R3, R3 and R4, R4 and R5) The same voltage as the voltage induced to the electrodes 62a, 62b, 62c, 62d electrically connected to is set. The first voltage divider R1 receives the anode voltage Va from the power supply 68, and the fifth voltage divider R5 is connected to the ground voltage source GND in the same manner as the cathode voltage Vg. The power supply 68 supplying the anode voltage Va to the first voltage divider R1 has a high input impedance Rin so that a constant voltage can be supplied at all times regardless of the state of the FED.

The operation characteristics of the voltage supply unit 66 will be described in detail on the assumption that predetermined voltages Va and Vg are applied to the anode electrode and the cathode electrode. Predetermined voltages are induced to the electrodes 62a, 62b, 62c, and 62d by the voltages applied to the anode and cathode electrodes. The diodes D1, D2, D3, and D4 are applied with the same voltage as the voltage induced to the electrodes 62a, 62b, 62c, and 62d electrically connected to them. While the FED displays the image, charges are accumulated in the spacer 60 by the electron beam diffusion phenomenon. At this time, since a predetermined voltage is induced in the electrodes 62a, 62b, 62c, and 62d, charges accumulated in the spacer 60 are moved to the electrodes 62a, 62b, 62c, and 62d positioned adjacent to the electrodes. The charges transferred to the electrodes 62a, 62b, 62c, 62d pass through the ammeter A, the node points 70, 72, 74, 76 and the resistors R1 ', R2', R3 ', R4. It is moved to the voltage source GND. That is, the charge accumulated in the spacer 60 is moved to and removed from the electrodes 62a, 62b, 62c, and 62d. At this time, the ammeter A displays the amount of current moved through it. That is, the amount of current accumulated in the spacer 60 is displayed. Ammeters A provided between the node points and the electrodes 62a, 62b, 62c, 62d and indicating the amount of current accumulated in the spacer 60 may be omitted. . On the other hand, the voltage values induced in the electrodes 62a, 62b, 62c, 62d are not always constant and periodically change, but the diodes are divided by the voltage value induced in the electrodes 62a, 62b, 62c, 62d and the voltage divider resistance. The voltage values applied to the fields D1, D2, D3, and D4 are always the same (V1 = V1 ', V2 = V2', V3 = V3 ', V4 = V4'). For example, if the voltage V1 'induced to the first electrode 62a has a voltage value lower than the voltage V1 applied between the first and second voltage divider resistors R1 and R2, the induced voltage ( V1 ') and the first diode D1, the node point from the voltage V1 between the voltage dividing resistors R1 and R2 until the voltage V1 between the first and second voltage dividing resistors R1 and R2 becomes equal. Current flows to the ground voltage source GND via 70 and resistor R1 '. Accordingly, the voltage values induced to the electrodes 62a, 62b, 62c, and 62d and the voltage values applied to the diodes D1, D2, D3, and D4 by the voltage dividing resistor are always the same (V1 = V1 ', V2 =). V2 ', V3 = V3', V4 = V4 ').

As described above, according to the field emission display device according to the present invention, a plurality of electrodes may be formed on the surface of the spacer, and different voltages may be applied to the electrodes to remove charges accumulated in the spacer. Therefore, discharge unevenness and arcing phenomenon of the field emission display device can be prevented.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (5)

An upper substrate; A lower substrate installed to face the upper substrate; An anode electrode installed on the upper substrate; A cathode electrode disposed on the lower substrate; A spacer disposed between the upper substrate and the lower substrate to support the upper substrate and the lower substrate; A plurality of electrodes provided on a surface of the spacer; A voltage supply for supplying different voltages to the electrodes; The voltage supply unit includes voltage divider resistors for supplying the different voltages to the electrodes, diodes disposed between the electrodes and the voltage divider resistors to prevent reverse current flowing from the electrodes toward the voltage divider resistors; And a resistor provided between the node point between the diode and the electrode and a ground voltage source to supply charge accumulated in the electrode to the ground voltage source. The method of claim 1, And a power supply for supplying an anode voltage supplied to said anode electrode and a cathode voltage supplied to said cathode electrode. The method of claim 2, And the voltage supply unit supplies the electrodes with a voltage equal to an induced voltage induced in the electrodes by the anode voltage and the cathode voltage. The method of claim 1, And the voltage supply unit further includes an ammeter disposed between the diode and the resistors to measure an amount of current flowing from the electrodes to the base voltage source. delete