KR20080085585A - Plasma display device and method for image sticking minimization thereof - Google Patents

Abstract

A plasma display apparatus and a method for removing image sticking thereof are provided to prevent phosphor degradation of a panel and minimize the image sticking by lowering frequencies of output images in still pictures. In a method for removing image sticking of a plasma display apparatus driven by plural sub-fields having different illumination numbers, current display image signals are received(S10). It is determined whether or not the image signals are still pictures(S20). When the image signals are still pictures, the number of sustain pulses of the sub-fields is reduced(S30). At the same time, an output frequency of the image signals is reduced(S40). The output frequency, which is a vertical frequency, is reduced to 1Hz through 10Hz.

Description

Plasma Display Device and Method for Image Sticking Minimization

1 is a diagram illustrating an embodiment of a structure of a plasma display panel;

2 illustrates an embodiment of an electrode arrangement of a plasma display panel;

FIG. 3 illustrates an embodiment of a method in which one frame of an image is time-divided and driven into a plurality of subfields in a plasma display device.

FIG. 4 is a diagram illustrating an embodiment of applying an ISM mode to a plasma display device.

5 is a view for explaining a method of removing the afterimage of the plasma display device according to the present invention.

Figure 6 is a view sequentially showing an embodiment of the afterimage removal method according to the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma display device and a method for removing afterimages thereof. In particular, in the case of a still image, an image sticking minimization mode operation and a frequency of an output image are lowered to prevent deterioration of phosphors in a panel and to reduce afterimages as much as possible. And a method for removing afterimages thereof.

In general, a plasma display panel (hereinafter referred to as a PDP) generates a discharge by applying a predetermined voltage to electrodes installed in a discharge space, and the plasma generated during gas discharge excites a phosphor, thereby causing an image including a character or graphic. As a device for displaying a display device, it is easy to increase in size, light weight, and planar thickness, and provides a wide viewing angle up, down, left, and right, and realize full color and high brightness.

Such a plasma display apparatus is time-division-driven one frame into several subfields having different number of emission times in order to realize gray level of an image. In addition, each subfield is divided into a reset section for uniformly generating a discharge, an address section for selecting a discharge cell, and a sustain section for implementing gray levels according to the number of discharges.

In this case, when the screen displayed on the plasma display apparatus displays the same image, that is, a still image or the same gray level, for a predetermined time, there is a problem that an afterimage occurs on the screen.

The present invention has been made to improve the above-described problems of the prior art, and when the same image or the image having the same gradation is displayed on the screen for a predetermined time, the afterimage of the screen is generated by varying the output frequency of the image It is an object of the present invention to provide a plasma display device that can be prevented as much as possible.

In the plasma display apparatus of the present invention for solving the above-described technical problems, a frame is divided into a plurality of subfields having different number of emission times, and the APL between each frame is equal to 1 or more times for a certain time. In the case of difference of 3 to 3, the number of sustain pulses of each of the plurality of subfields is reduced and driven. When the currently displayed image is the same screen or the APL is different from 1 to 3 for each frame for a predetermined time, the image It characterized by reducing the output frequency of.

At this time, the output frequency is reduced to 1 kHz to 10 kHz, it will be preferred that the vertical frequency.

In accordance with an aspect of the present invention, there is provided a method of removing an afterimage of a plasma display device according to the present invention, comprising: a first step of determining whether a still image is received by receiving an image signal currently displayed; A second step of reducing the number of sustain pulses of each of the subfields, if the image is still; And a third step of reducing the number of sustain pulses and simultaneously reducing an output frequency of the video signal.

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

1 is a perspective view showing an embodiment of a plasma display panel according to the present invention.

Referring to FIG. 1, a plasma display panel includes a scan electrode 11 and a sustain electrode 12, which are pairs of sustain electrodes formed on an upper substrate 10, and an address electrode 22 formed on a lower substrate 20. Include.

Each of the sustain electrode pairs 11 and 12 is typically a transparent electrode 11a or 12a formed of indium tin oxide (ITO), a metal such as silver (Ag), chromium (Cr), or chromium / copper. And the bus electrodes 11b and 12b which can be formed in a stacked type of / chromium (Cr / Cu / Cr) or a stacked type of chromium / aluminum / chromium (Cr / Al / Cr). At this time, the bus electrodes 11b and 12b are formed on the transparent electrodes 11a and 12a to reduce the voltage drop caused by the transparent electrodes 11a and 12a having high resistance.

Meanwhile, the sustain electrode pairs 11 and 12 according to an embodiment of the present invention have not only a structure in which the transparent electrodes 11a and 12a and the bus electrodes 11b and 12b are stacked, but also without the transparent electrodes 11a and 12a. Only the bus electrodes 11b and 12b may be formed. This structure does not use the transparent electrodes (11a, 12a), there is an advantage that can lower the cost of manufacturing the panel. The bus electrodes 11b and 12b used in such a structure may be various materials such as photosensitive materials in addition to the materials listed above.

In addition, the plasma display panel has a function of light blocking to reduce the reflection and absorption of external light generated from the outside of the upper substrate 10, the purity of the upper substrate 10, and the contrast of the PDP. Black Matrix (BM) is formed that improves.

The black matrix 15 according to the embodiment of the present invention is formed on the upper substrate 10, and the first black matrix 15 and the transparent electrodes 11a, which are formed at positions overlapping the partition wall 21 are formed. The second black matrixes 11c and 12c formed between 12a and the bus electrodes 11b and 12b may be formed. Here, the first black matrix 15 and the second black matrices 11c and 12c, also referred to as black layers or black electrode layers, may be simultaneously formed and physically connected in the forming process, and may not be simultaneously formed to be physically connected. It may be.

In addition, when physically connected and formed, the first black matrix 15 and the second black matrix 11c and 12c may be formed of the same material, but may be formed of different materials when they are physically separated.

The upper dielectric layer 13 and the protective layer 14 are stacked on the upper substrate 10 on which the scan electrode 11 and the sustain electrode 12 are formed, respectively. Charged particles generated by the discharge are accumulated in the upper dielectric layer 13, and the protective electrode pairs 11 and 12 may be protected. The protective layer 14 protects the upper dielectric layer 13 from sputtering of charged particles generated during gas discharge and increases emission efficiency of secondary electrons.

In addition, a lower dielectric layer 24 and a partition wall 21 are formed on the lower substrate 20 on which the address electrode 22 is formed. On the surfaces of the lower dielectric layer 24 and the partition wall 21, a phosphor 23 is emitted by ultraviolet rays generated during gas discharge to generate visible light. The partition wall 21 includes a vertical partition wall 21a formed in a direction parallel to the address electrode 22 and a horizontal partition wall 21b formed in a direction crossing the address electrode 22 to physically distinguish discharge cells. Ultraviolet rays and visible light generated by the discharge are prevented from leaking to the adjacent discharge cells.

Meanwhile, in an embodiment of the present invention, not only the structure of the partition wall 21 illustrated in FIG. 1, but also the structure of the partition wall 21 having various shapes may be possible. For example, a channel in which a channel usable as an exhaust passage is formed in at least one of the differential partition structure, the vertical partition 21a, or the horizontal partition 21b having different heights of the vertical bulkhead 21a and the horizontal bulkhead 21b. A grooved partition structure in which a groove is formed in at least one of the type partition wall structure, the vertical partition wall 21a, or the horizontal partition wall 21b may be possible.

Here, in the case of the differential barrier rib structure, the height of the horizontal barrier rib 21b is more preferable, and in the case of the channel barrier rib structure or the groove barrier rib structure, the channel or groove is formed in the horizontal barrier rib 21b. Would be desirable.

Further, in one embodiment of the present invention, although each of the R, G and B discharge cells are shown and described as being arranged on the same line, it will be possible to arrange them in other formations. For example, a delta type arrangement in which R, G, and B discharge cells are arranged in a triangular shape may be possible, and the shape of the discharge cell may be not only square but also various polygonal shapes such as pentagon and hexagon.

FIG. 2 illustrates an embodiment of an electrode arrangement of a plasma display panel, and a plurality of discharge cells constituting the plasma display panel is preferably arranged in a matrix form as shown in FIG. 2.

The plurality of discharge cells are provided at the intersections of the scan electrode lines Y1 to Ym, the sustain electrode lines Z1 to Zm, and the address electrode lines X1 to Xn, respectively. The scan electrode lines Y1 to Ym may be driven sequentially or simultaneously, and the sustain electrode lines Z1 to Zm may be driven simultaneously. The address electrode lines X1 to Xn may be driven by being divided into odd-numbered lines and even-numbered lines, or sequentially driven.

Since the electrode arrangement shown in FIG. 2 is only an embodiment of the electrode arrangement of the plasma panel according to the present invention, the present invention is not limited to the electrode arrangement and driving method of the plasma display panel shown in FIG. 2. For example, a dual scan method in which two scan electrode lines among the scan electrode lines Y1 to Ym are simultaneously scanned may be possible. In addition, the address electrode lines X1 to Xn may be driven by being divided up and down in the center portion of the panel.

3 is a timing diagram illustrating an embodiment of a time division driving method by dividing a frame into a plurality of subfields. The unit frame may be divided into a predetermined number, for example, eight subfields SF1, ..., SF8 to realize time division gray scale display. Each subfield SF1, ... SF8 is divided into a reset section (not shown), an address section A1, ..., A8 and a sustain section S1, ..., S8.

Here, according to an embodiment of the present invention, the reset period may be omitted in at least one of the plurality of subfields. For example, the reset period may exist only in the first subfield or may exist only in a subfield about halfway between the first subfield and all the subfields.

In each address section A1, ..., A8, an address signal is applied to the address electrode X, and a scan signal corresponding to each scan electrode Y is sequentially applied by one scan electrode line. In each of the sustain periods S1, ..., S8, a sustain signal is alternately applied to the scan electrode Y and the sustain electrode Z, so that wall charges are formed in the address periods A1, ..., A8. Sustain discharge occurs in the discharge cells.

The luminance of the plasma display panel is proportional to the number of sustain discharge pulses in the sustain discharge periods S1, ..., S8 occupied in the unit frame. When one frame forming one image is represented by eight subfields and 256 gradations, each subfield in turn has different sustains at a ratio of 1, 2, 4, 8, 16, 32, 64, and 128. The number of signals can be assigned. In order to obtain luminance of 133 gradations, cells may be sustained by addressing the cells during the subfield 1 section, the subfield 3 section, and the subfield 8 section.

The number of sustain discharges allocated to each subfield may be variably determined according to weights of the subfields according to the APC (Automatic Power Control) step. That is, in FIG. 3, a case in which one frame is divided into eight subfields has been described as an example. However, the present invention is not limited thereto, and the number of subfields forming one frame may be variously modified according to design specifications. . For example, a plasma display panel may be driven by dividing one frame into eight or more subfields, such as 12 or 16 subfields. The number of sustain discharges allocated to each subfield can be variously modified in consideration of gamma characteristics and panel characteristics. For example, the gray level assigned to subfield 4 may be lowered from 8 to 6, and the gray level assigned to subfield 6 may be increased from 32 to 34.

The PDP driven as described above generates the same sustain discharge in each of the plurality of subfields to express the same even when the same screen is continuously displayed or the same gray level is displayed for a predetermined period of time. In this case, since the corresponding phosphor must be turned on continuously in order to display the same screen and gradation, deterioration of the phosphor occurs. As a result, an afterimage problem occurs on the screen when the gray level is changed or the screen is changed to another screen. In order to prevent such a problem, the present invention preferentially uses a conventional image sticking minimization (ISM) mode, that is, a drive that detects that the same screen is displayed and reduces the number of sustain pulses.

FIG. 4 is a diagram illustrating an embodiment of applying an ISM mode in a plasma display apparatus.

Referring to FIG. 4, after detecting a still image or the same gray level, the ISM mode is operated and the number of sustain pulses is reduced to drive the PDP. For example, a picture of a PDP in which one frame is divided into a plurality of subfields from the first subfield SF1 to the Nth subfield SF N has a still image or an APL difference between each frame for a predetermined time. If there is a difference, the ISM mode is activated, and the number of sustain pulses of each of the plurality of subfields is reduced. This means that the number of sustain discharges is reduced. As a result, the luminance of the PDP screen may be reduced. However, in the case of a still image, the luminance decrease of the screen does not significantly affect the image quality. Therefore, the number of sustain pulses is reduced. . Therefore, phosphor deterioration can be reduced and afterimage can be prevented to some extent.

As described above, although the degradation of the phosphor can be reduced as the number of sustain discharges is reduced by applying the ISM mode when driving the PDP, in the present invention to compensate for the residual problem that needs to be improved and to prevent the phosphor degradation as much as possible. After applying ISM mode, reduce the frequency of the output video.

5 is a view for explaining a method of removing the afterimage of the plasma display device according to the present invention.

Referring to FIG. 5, after the ISM mode is operated as an example (A), the number of sustain pulses in each subfield of one frame is reduced, and the number of sustains in each unit frame in which the number of sustain pulses is reduced is the same. There is a slight difference, and the output frequency before and after the ISM mode operation is the same, so the number of frames output during the same time is always constant.

In contrast, the present invention (B) is in the ISM mode of reducing the number of sustain pulses when the difference between the average picture level (APL) of each frame is 1 to 3 for a still image or for a predetermined time (about 3 to 6 minutes). At the same time as the operation, the frequency of the still image is reduced to output. For example, if the normal frequency of PDP and ISM mode are not in operation, the output frequency is 60Hz, and if ISM mode is applied when the PDP still image is applied, the output frequency is reduced to 50Hz to output the image at 10Hz per second. Since the frame degree is reduced, the number of sustain pulses corresponding to 10 frames can be reduced. In other words, when the output frequency of the PDP is driven at 60 Hz, one frame is about 16.67 Hz, and when one is driven at 50 Hz, one frame is about 20 Hz. Therefore, reducing the output frequency can reduce the number of frames for the same time. Will be. In such a case, the number of sustain pulses can be reduced by the ISM mode, and the number of sustain pulses can be further reduced due to the frequency reduction. In other words, if the number of sustain pulses in each subfield is excessively reduced, it has a great effect on the luminance deterioration and the screen realization, thereby reducing the number of sustain pulses in each subfield. However, the number of sustain pulses is reduced by reducing the output frequency. It is possible to reduce. At this time, the output frequency means the vertical frequency, and in the case of a still image, outputting the image by reducing the frequency to 1 ㎐ to 10 에만 only during ISM mode operation does not have a significant effect on image quality deterioration. It becomes possible. On the other hand, even if a still image is output to the PDP, if the frequency is reduced by more than 10 Hz, the image quality may be reduced due to flickering of the screen.

6 is a flowchart sequentially showing an embodiment of the afterimage removal method according to the present invention.

Referring to FIG. 6, a method for removing afterimages of a PDP according to the present invention includes a first step (S10 and S20) of determining whether a still image is received by receiving an image signal currently displayed; A second step (S30) of reducing the number of sustain pulses of each of the subfields if the image is still; And a third step S40 of reducing the number of sustain pulses and simultaneously reducing the output frequency of the video signal.

First, a video signal is input by a control unit (not shown) and a memory (not shown) included in the PDP to determine whether the image is a still image by comparing the previous image with the current image. If the image implemented by the current PDP is a still image, the controller operates the ISM mode to reduce the number of sustain pulses of each subfield, and also decreases the frequency of the output image and then outputs the still image (S50). In this case, the frequency is a vertical frequency, it will be preferable to reduce to 1kHz to 10kHz. In such a case, in the case of a still image, the number of sustain pulses is reduced by the ISM mode and the number of sustain pulses is reduced by the frame reduction due to the frequency reduction, thereby preventing deterioration of the phosphor and improving the afterimage problem. It becomes possible.

As described above, the plasma display device according to the present invention has been described with reference to the illustrated drawings, but the present invention is not limited by the embodiments and drawings disclosed herein, and is applied by those skilled in the art within the technically protected scope of the present invention. This is possible.

The plasma display device of the present invention configured as described above continuously reduces the frequency of the image output after the ISM mode and at the same time when the APL is different from 1 to 3 for each frame for a fixed time or a fixed time. Phosphor deterioration of the cell to be turned on (ON) can be reduced, and there is an effect of preventing the occurrence of afterimages.

Claims (5)

Divide one frame into multiple subfields with different flashes, In the plasma display apparatus in which the number of the sustain pulses of each of the plurality of subfields is reduced when the current displayed image is the same screen for a predetermined time or the APL is different from 1 to 3 for a predetermined time, The output display of the plasma display device, characterized in that for reducing the output frequency of the image when the current displayed image is the same screen or the APL between each frame for a certain time to 1 to 3. The method according to claim 1, And the output frequency is reduced to 1 kHz to 10 kHz. The method according to claim 1, And said output frequency is a vertical frequency. In the afterimage preventing method of the plasma display apparatus is driven by dividing one frame into a plurality of sub-fields having a different number of emission, A first step of determining whether a still image is received by receiving a currently displayed image signal; A second step of reducing the number of sustain pulses of each of the subfields, if the image is still; And And reducing the output frequency of the video signal while reducing the number of sustain pulses. The method according to claim 3, The output frequency is a vertical frequency, Afterimage removal method of the plasma display device, characterized in that reduced to 1㎐ ~ 10㎐.

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