1. Field of the Invention
The present invention relates to a method of driving a plasma display panel.
2. Description of the Related Art
As a display panel of matrix display scheme, there is known an AC (AC discharge) type plasma display panel. The AC-type plasma display panel comprises a plurality of column electrodes (address electrodes), and a plurality of row electrode pairs which are arranged orthogonal to the column electrodes and each of which forms one scan line. These row electrode pairs and column electrodes are covered with a dielectric layer through which a discharge space opposes. A discharge cell corresponding to one pixel is formed at an intersection of a row electrode pair with a column electrode.
As a method of displaying a halftone image on such a plasma display panel, a so-called sub-field method is known, where one field period is divided into N sub-fields in which light is emitted for a time corresponding to a weight for each bit digit of N-bit pixel data.
In the example shown in
Each sub-field is made up of an addressing period Wc, and a sustain period Ic. However, in the first sub-field, a reset period Rc is provided before the addressing period Wc. In the reset period Rc, all discharge cells of the plasma display panel are simultaneously excited to discharge (reset discharge) to uniformly form wall charges in all the discharge cells. In the next addressing period Wc, a selective erasure discharge is excited in accordance with pixel data for each discharge cell. In this event, the wall charge extinguishes in those discharge cells in which the erasure discharge has been performed, causing the discharge cells to become “unlit cells.” On the other hand, those discharge cells in which no erasure discharge has been performed are “lit cells” because the wall charges still remain therein. In the sustain period Ic, only the lit cells are forced to continue a discharge light emission state for a time corresponding to a weight for each sub-field. In this way, in the respective sub-fields SF1-SF6, the light emission is sustained in a light emission period ratio of 1:2:4:8:16:32 in order. A driving method which involves forming wall charges in all display cells at the beginning of the sub-field SF1, and selectively erasing the wall charge formed in each display cell in the addressing period Wc of the subsequent sub-fields SF1-SF6 in the foregoing manner is called a selective erasure addressing method.
Generally, in the plasma display panel, a plurality of row electrode pairs are arranged in parallel with each other to extend in the row direction on a front glass substrate, while a plurality of column electrodes are arranged to extend in the column direction on a back substrate.
In the sustain state, a sustain pulse IPX is repeatedly applied to the row electrodes, and a sustain pulse IPY is repeatedly applied to the row electrodes Y at a time point shifted from that of the sustain pulse IPX. For each time the sustain pulses IPX, IPY are applied, a sustain discharge occurs between the row electrodes in a discharge cell which is in the “lit cell” state. The number of times the sustain pulses IPX and IPY are applied in each sub-field is set in accordance with a weight for each sub-field, as shown in
In the addressing period of the sub-field SFi, as a scan pulse is applied to the row electrode Y at the same time a high-voltage pixel data pulse is applied to the column electrode D, a selective erasure discharge occurs with a discharge current flowing in a direction indicated by an arrow between the column electrode D and the row electrode Y. Thus, this discharge cell changes to an “unlit cell.” At the end of the addressing period, positive wall charges + are formed on both the row electrodes X and Y, while a negative wall charge − is formed on the column electrode D. Therefore, even if the sustain pulse IPY is applied to the row electrode in the subsequent sustain period of the sub-field SFi, or even if the sustain pulse IPX is applied to the row electrode X, no sustain discharge will occur between the row electrode Y and the row electrode X.
Another known plasma display panel includes a co-planar configuration panel which has a plurality of row electrode pairs arranged in parallel with each other to extend in the row direction on a front glass substrate, a plurality of column electrodes arranged in parallel in the column direction on the front glass substrate, and protrusions of the column electrodes in a discharge gap between the row electrode pairs of the respective discharge cells, other than the panel which has the column electrodes arranged on a back substrate.
As shown in
It is an object of the present invention to provide a driving method which is capable of preventing erroneous discharges even if a selective erasure addressing method is applied to a plasma display panel which has both column electrodes and row electrodes arranged on a front substrate.
A plasma display panel driving method of the present invention is a method of driving a plasma display panel in accordance with an image signal, the plasma display panel having a pair of substrates opposing across a discharge space, a plurality of row electrode pairs corresponding to display lines and extending in a row direction and a plurality of column electrodes disposed between the pair of substrates, to respectively form discharge cells in portions of the discharge space opposing regions surrounded by row electrodes constituting the respective row electrode pairs and the column electrodes adjacent to each other, at least one of the row electrodes constituting each of the row electrode pairs and each of the column electrodes being formed on one of the pair of substrates, wherein: one field display period of the image signal is divided into a plurality of sub-fields, the method comprising the steps of: executing in each of the sub-fields, an addressing stage for sequentially applying a scan pulse to one row electrodes of the row electrode pairs, and applying pixel data pulses corresponding to the image signal to the column electrodes to produce a selective erasure discharge for setting each of the discharge cells to one of a lit cell state and an unlit cell state, and a sustain stage for applying a sustain pulse to the row electrodes constituting each of the row electrode pairs a number of times corresponding to a weight for the sub-field to produce a sustain discharge only in the discharge cell in the lit cell state; and simultaneously applying wall charge adjusting pulses having a same polarity as the sustain pulse to the row electrodes formed in pair for a predetermined period in each of the sub-fields after the addressing stage terminates and before the sustain stage starts.
In the following, embodiments of the present invention will be described in detail with reference to the drawings.
As shown in
The PDP 50 is formed with column electrodes D1-Dm respectively extending in a vertical direction of a two-dimensional display screen, and row electrodes X1-Xn and row electrodes Y1-Yn respectively extending in the horizontal direction of the two-dimensional display screen. In this event, row electrode pairs (Y1, X1), (Y2, X2), (Y3, X3), . . . , (Yn, Xn), which form pairs with adjacent ones to each other, form a first display line to an n-th display line on the PDP 50. At the intersection of each display line with each of the column electrodes D1-Dm (an area surrounded by a one-dot chain line in
Each of the column electrodes D1-Dm of the PDP 50 is connected to the column electrode driving circuit 55, each of the row electrodes X1-Xn is connected to the X-row electrode driving circuit 51, and each of the row electrodes Y1-Yn is connected to the Y-row electrode driving circuit 53.
The driving control circuit 56 supplies each of the X-electrode driver 51, Y-electrode driver 53, and address driver 55 with a variety of control signals for driving the PDP 50 having the foregoing structure in accordance with a light emission driving sequence which employs a sub-field method (sub-frame method) as shown in
FIGS. 5 to 8 show an example of the PDP 50, where
In these FIGS. 5 to 8, a plurality of electrode pairs (X, Y) are arranged on the front glass substrate 1, which forms a display plane, in parallel to extend in the row direction (horizontal direction in
The row electrode X comprises a transparent electrode Xa formed in a T-shape and made of a transparent conductive film such as ITO, and a bus electrode Xb made of a black or a dark metal film, extending in the row direction of the front glass substrate 1, and connected to a narrow proximal end of the transparent electrode Xa.
Likewise, the row electrode Y comprises a transparent electrode Ya formed in a T-shape and made of a transparent conductive film such as ITO, and a bus electrode Yb made of a black or a dark metal film, extending in the row direction of the front glass substrate 1, and connected to a narrow proximal end of the transparent electrode Ya.
These row electrodes X, Y are alternately arranged in the column direction (vertical direction in
On the back surface of the front glass substrate 1, a black or a dark light absorbing layer (light shielding layer) 2 is formed between the bus electrodes Xb, Yb, in parallel with each other, of adjacent row electrode pairs (X, Y) in the column direction to extend in the row direction along the bus electrodes Xb, Yb.
A first dielectric layer 3 is formed on the back surface of the front glass substrate 1 to cover the row electrode pairs (X, Y) and light absorbing layer 2.
On the back surface side of the first dielectric layer 3, column electrode bodies Da, which form part of the column electrodes D, are arranged in parallel with a predetermined spacing defined therebetween, such that they extend in a direction orthogonal to the row electrode pairs (X, Y) (column direction) at positions which oppose intermediate positions of the respective transparent electrodes Xa, Xb which are arranged at equal intervals in the row direction along bus electrodes Xb, Yb of the row electrodes X, Y.
On the back surface side of the first dielectric layer 3, a column electrode discharge portion Db, which forms part of the column electrode D, is integrally formed in the row direction from one side of each column electrode body Da for each display line L, such that its leading end is positioned at a position which opposes an intermediate position of the discharge gap g between the transparent electrodes Xa and Ya of each electrode pair (X, Y).
A second dielectric layer 4 is formed on the back surface of the first dielectric layer 3 to cover the column electrode body Da and column electrode discharge portion Db of this column electrode D.
On the back surface side of the second dielectric layer 4, a raised dielectric layer 4A projecting toward the back surface of the second dielectric layer is formed at a position opposing the light absorbing layer 2 positioned between the bus electrodes Xb, Yb of row electrode pairs (X, Y) adjacent to each other, to extend in the row direction along the bus electrodes Xb, Yb. Further, a protection layer made of MgO, not shown, is formed on the back surface sides of the second dielectric layer 4 and raised dielectric layer 4a.
On the other hand, on the display surface of the back glass substrate 5 opposing the front glass substrate 1 across a discharge space, gridded partitions 6 are formed of vertical walls 6A formed at positions opposing the column electrode bodies Da on the front glass substrate 1 side to respectively extend in the column direction, and horizontal walls 6B formed at positions opposing the bus electrodes Xb, Yb positioned back-to-back of the row electrode pairs (X, Y) adjacent to each other and the light absorbing layer 2 positioned therebetween to extend in the row direction, respectively, and the discharge space between the front glass substrate 1 and the back glass substrate 5 is partitioned into portions opposing the paired transparent electrodes Xa, Ya in each row electrode pair (X, Y) to form respective rectangular discharge cells C.
The surface of the vertical wall 6A of this partition 6 on the display side surface is not in contact with the protection layer which covers the raised dielectric layer 4A (see
On the side surfaces of the vertical walls 6A and horizontal walls 6B of the partitions 6 facing the discharge cells C, and the surface of the back glass substrate 5, a fluorescent material layer 7 is formed to cover all of these five surfaces, and the colors of the fluorescent material layer 7 are arranged such that the discharge cells C of three primary colors, red, green, blue, are arranged side by side in the row direction in order.
Also, a discharge gas including xenon Xe is filled in the discharge space between the front glass substrate 1 and the back glass substrate 5.
In the plasma display device, a selective erasure addressing method is applied in a light emission driving sequence as shown in
In the sustain period after the end of the addressing period W in each of the sub-fields SF1-SFN, before first sustain pulses IPX, IPY are applied to the row electrodes X1-Xn and row electrodes Y1-Yn, a first wall charge adjusting pulse is applied to the row electrodes X1-Xn, and simultaneously a second wall charge adjusting pulse is applied to the row electrodes Y1-Yn.
At the beginning of each sustain period of the sub-fields SFi-1 and SFi, the first wall charge adjusting pulse is applied to the row electrode X, and simultaneously the second wall charge adjusting pulse is applied to the row electrode Y. In this way, only in those discharge cells in which a selective erasure discharge has occurred in the preceding addressing period, such as the sub-field SFi, a discharge current flows between the row electrode pair X, Y and the column electrode in a direction as shown by an arrow in
In a discharge cell in which no selective erasure discharge occurs in the addressing period of the sub-field SF1, the polarity of the wall charge on each of the row electrode pairs and column electrode remains in the same state as that at the end of the sustain period of the sub-field SFi-1, so that the set “lit cell” state is maintained. Therefore, even if the first and second wall charge adjusting pulses are applied in the sustain period of the sub-field SFi, no discharge occurs between the row electrodes and the column electrode, and with subsequent application of each of the first sustain pulses IPX, IPY, a sustain discharge occurs on a separate basis, and subsequently, sustain discharge light emission is repeated each time the sustain pulses are applied.
In the embodiment shown in
In a discharge cell in which no selective erasure discharge occurs in the addressing period of the sub-field SFi, the polarity of the wall charge on each of the row electrode pair and column electrode is in the same state in the period T1 in which the first and second wall charge adjusting pulses are being applied as that at the end of the sustain period in the sub-field SFi-1, so that the set “lit cell” state is continued. Therefore, even if the first and second wall charge adjusting pulses are both applied in the sustain period of the sub-field SFi, no discharge occurs between the row electrodes and the column electrode, and with subsequent application of each of the first sustain pulses IPX, IPY, a sustain discharge occurs on a separate basis, and subsequently, sustain discharge light emission is repeated each time the sustain pulses are applied.
The PDP 50 is not limited to the panel in the structure shown in FIGS. 5 to 8, but may be a panel in a structure as shown in
Also, the PDP 50 may be a panel which has one electrode (row electrode) of the row electrode pair and the column electrode D on the front glass substrate, and the other row electrode (row electrode X) of the row electrode pair on the back substrate, and performs a sustain discharge with an opposite discharge.
The embodiment described above employs a one-reset, one-selective erasure addressing method which divides one field into a plurality of sub-fields, where all discharge cells are set to a lit cell state prior to the addressing period only in the first sub-field, and an erasure discharge is selectively produced in accordance with pixel data in the addressing period of one of the sub-fields to keep the sub-field in the lit state until an erasure discharge occurs. In this addressing method, the display can be made in N+1 halftone levels with N sub-fields. The present invention is not limited to this one-reset, one-selective erasure addressing method, but can be applied to a sequence which involves setting all discharge cells once in a lit state in a reset stage in each of the sub-fields, selectively producing an erasure discharge in accordance with pixel data in the subsequent addressing stage, and displaying in 2N halftone levels with N sub-fields.
As described above, according to the present invention, the wall charge adjusting pulses having the same polarity as the sustain pulse are simultaneously applied to the respective row electrodes in pair for a predetermined period after the addressing period terminates and before the sustain period starts in each sub-field, so that even if the first sustain pulse is subsequently applied to the row electrode pair, an erroneous discharge is prevented from occurring between the row electrodes and the column electrode, thus avoiding a discharge cell which has been set to an unlit cell in the addressing period from changing to a lit cell.
This application is based on Japanese Patent Application No. 2005-079447 which is hereby incorporated by reference.
Number | Date | Country | Kind |
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2005-079447 | Mar 2005 | JP | national |