KR100727304B1 - Driving method of field emission display device - Google Patents

Abstract

The present invention relates to a method of driving a field emission display device capable of expressing linear gray scales.

A method of driving a field emission display device according to the present invention includes driving one frame into a plurality of subfields, assigning a same time to each subfield, and applying different voltages to the anode electrodes.

According to the present invention, a linear gray scale can be expressed by dividing one frame into eight subfields and setting different time and / or anode voltages applied to each subfield.

Description

Driving method of field emission display device {Driving Method of Field Emission display}             

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

FIG. 2 is a cross-sectional view illustrating the field emission display device illustrated in FIG. 1. FIG.

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

4A and 4B are diagrams illustrating a gradation representation method of a conventional field emission display device.

FIG. 5 is a diagram showing one frame divided into several subfields by the gradation expression method according to the first embodiment of the present invention; FIG.

FIG. 6 is a diagram illustrating an anode voltage applied to a subfield illustrated in FIG. 5. FIG.

FIG. 7 is a diagram illustrating a linear gray scale represented by an anode voltage applied to FIG. 6.

Fig. 8 is a diagram showing one frame divided into several subfields by the gray scale expression method according to the second embodiment of the present invention.

<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: spacer

42: gate driver 44: cathode driver

46: control unit 48: pixel

50: group

The present invention relates to a method of driving a field emission display device, and more particularly, to a method of driving a field emission display device capable of expressing linear gray scales.

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 illustrate a conventional field emission display device.

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.

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.

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 42 connected to m gate electrode lines R to sequentially enable respective gate electrode lines R; A first cathode driver 44A which is connected to the odd-numbered cathode electrode lines C and sequentially supplies image data to the gate electrode lines R during the period in which the gate electrode lines R are enabled, and A second cathode driver 44B which is connected to the first cathode electrode lines C and sequentially supplies image data to the gate electrode lines R during the period in which the gate electrode lines R are enabled, and the gate driver A control unit 46 for controlling the 42 and the cathode drive unit 44 is provided. 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 42 sequentially supplies scan pulses to the first to m th gate electrodes R1 to Rm. The cathode driver 44 is 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 detail, the scan pulse is first supplied from the gate driver 42 to the first gate electrode line R1 in response to a control signal of the controller 46. When the scan pulse is supplied to the first gate electrode line R1, the image data is supplied to the first to nth cathode electrode lines C1 to Cn. When image data is supplied to the cathode electrode lines C, electrons corresponding to the image data are emitted from the pixels 48. Electrons emitted from the pixels 48 collide with the phosphor 6 to excite the phosphor 6. At this time, visible light of any one of red, green, and blue colors is generated in accordance with the phosphor 6 to display an image. Conventionally, pulse amplitude modulation (hereinafter referred to as "PAM") has been used to express the amount of electrons emitted, that is, the gray level. The gray scale representation method will be described in detail with reference to FIGS. 4A to 4B. 4A is a diagram illustrating a pulse applied to the cathode electrode line C when representing 256 gray levels. When a scan pulse is applied to the gate electrode line R, a predetermined voltage capable of expressing 256 gray levels is applied to the cathode electrode line C. When representing 128 gray levels, a voltage corresponding to half of 256 gray levels is applied to the cathode electrode line C as shown in FIG. 4B. That is, conventionally, 256-gradation images were expressed by changing the amplitude of the image data applied to the cathode electrode line (C).

In order to express 256 gray levels through the change in amplitude as described above, it is required to be applied to the cathode electrode line C having a high voltage. Therefore, since the gray level is expressed by dividing the voltage below predetermined value by 256 equally, the linear gray level cannot be expressed.

Accordingly, an object of the present invention is to provide a method of driving a field emission display device capable of expressing linear gray scales.

In order to achieve the above object, the method of driving the field emission display device according to the present invention includes driving one frame divided into a plurality of subfields, assigning the same time to each subfield, and applying different voltages to the anode electrodes. The steps are as follows.

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. 5 to 8.

5 and 6 are diagrams illustrating a gray scale expression method according to a first embodiment of the present invention.

5 and 6, in the first embodiment of the present invention, one frame is divided into eight subfields and driven to express gray scales. The gray level value of each subfield is increased at a rate of ²ⁿ (n = 0, 1, 2, 3, 4, 5, 6, 7). That is, each subfield represents 1, 2, 4, 8, 16, 32, 64, and 128 gray levels. While the time allocated to each subfield is the same to express such gray scale, the voltage applied to the anode electrode is different in each subfield. That is, in the first subfield SF1, a low voltage is applied to the anode electrode so as to express a gray scale of "1". In the eighth subfield SF8, a high voltage is applied to express the gray level of " 128 &quot;. That is, in the gradation expression method according to the first embodiment of the present invention, the time allocated to each subfield is the same, while the anode voltage allocated to each subfield is different. In order to express the gray scale, the anode voltage increases from the first subfield SF1 to the eighth subfield SF8. Therefore, in the first embodiment of the present invention, a frame is divided into eight subfields to be driven, and a linear gray scale can be expressed as shown in FIG. 7 by controlling the magnitude of the anode voltage applied to each subfield.

8 is a diagram illustrating a gray scale expression method according to a second embodiment of the present invention.

Referring to FIG. 8, in the second embodiment of the present invention, one frame is divided into eight subfields to represent gray scales. Each subfield is divided into four groups 50, 52, 54, and 56, and the times allocated to the groups 50, 52, 54, and 56 are different from each other. Also, the time applied to each of the groups 50, 52, 54 and 56 is the same as each other. Here, the anode voltages applied to the groups 50, 52, 54, and 56 are the same.

That is, in the second embodiment of the present invention, the gray level is expressed by dividing the eight subfields into four groups and varying the time applied to the four groups. At this time, the time allocated to the subfield is longer from the first group 50 to the second group 56. That is, the time of t is allocated to the first group 50, and t1, which is more time than t allocated to the first group, is allocated to the second group 52. In addition, the third group 54 is allocated a time of t2 which is more time than t1 allocated to the second group, and the fourth group 56 is allocated a time of t3 which is more time than t2 allocated to the third group. do. In this way, the gray scales are expressed by varying the time applied to each of the groups 50, 52, 54, and 56. Further, in the second embodiment of the present invention, gray levels may be expressed by different anode voltages applied to respective groups. That is, gray scales are represented by different times and anode voltages allocated to each group. In addition, in the second embodiment of the present invention, the anode voltages applied to the respective subfields SF1 to SF8 are different so that more accurate gray scales can be expressed. Accordingly, in the second embodiment of the present invention, linear gray scales can be expressed.

As described above, according to the driving method of the field emission display device according to the present invention, one frame is divided into eight subfields, and time and / or anode voltages applied to the respective subfields are set differently so that linear gray levels are obtained. I can express it.

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 (9)

In the driving method of the field emission display device having an anode electrode and is driven in units of frames, Driving one frame divided into a plurality of subfields; And allocating different voltages to each of the subfields and applying different voltages to the anode electrodes. The method of claim 1, And the frame is divided into eight subfields. The method of claim 1, And the anode voltage is set in each of the subfields so that the voltage level thereof increases in proportion to the luminance contrast. The method of claim 1, Wherein each subfield is divided into two or more groups, and different times are allocated to the respective groups. The method of claim 4, wherein And the groups comprise two or more subfields. The method of claim 4, wherein And the time applied to the groups is set in each of the groups such that the time is increased in proportion to the luminance contrast. The method of claim 4, wherein And an anode voltage applied to subfields included in the same group among the groups. The method of claim 4, wherein The anode voltage applied to the subfields included in the respective groups is different from each other. The method of claim 8, The time applied to the groups and the anode voltage applied to the subfields included in the groups are set to increase in proportion to the luminance contrast.

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