Patent Grant
7755285
The present application claims priority from Japanese patent application No. JP 2004-345575 filed on Nov. 30, 2004 and No. 2005-300008 filed on Oct. 14, 2005, the contents of which are hereby incorporated by reference into this application.
The present invention relates to an AC plasma display apparatus (PDP apparatus) used in a display unit such as a personal computer or work station, a flat television, or a plasma display (PDP) for displaying advertisements, and information, etc.
One of commercially-available AC color PDPs is a three-electrode-type PDP in which a plurality of first electrodes and a plurality of second electrodes extending in a first direction are alternately provided in parallel and a plurality of third electrodes extending in a second direction perpendicular to the first direction are provided in parallel.
In a general structure of the three-electrode type PDP, first (X) electrodes and second (Y) electrodes are alternately provided in parallel on a first substrate, third (address) electrodes extending in the direction perpendicular to the first and second electrodes are provided on a second substrate facing the first substrate, and each surface of the electrodes is covered with a dielectric layer. Between the third electrodes on the second substrate, there are further provided one-directional stripe-shaped barrier ribs extending in parallel with the third electrodes or a two-dimensional grid-shaped barrier rib arranged in parallel with the third electrodes and the first and second electrodes so that the cells are separated from one another. After phosphor layers are formed between the barrier ribs, the first and second substrates are bonded together.
After the charges (wall charges) in the vicinity of the electrode in each cell are brought into a uniform state by applying a voltage between the first and second electrodes, a scan pulse is sequentially applied to the second electrode and an address pulse is applied to the third electrode in synchronization with the scan pulse and an addressing operation is performed to selectively leave the wall charges in the cell to be turned on. Then, by applying a sustain discharge pulse by which the two adjacent electrodes to be discharged become electrodes having alternately opposite polarities to perform the addressing operation, the cell to be turned on, in which the wall charges are left, makes a sustain discharge and is turned on. The phosphor layer emits light by the ultraviolet rays generated by the discharge, and the emitted light is seen through the first substrate. For this purpose, the first and second electrodes are each composed of an opaque bus electrode made of a metal material and a transparent electrode (discharge electrode) such as an ITO film, and the light generated in the phosphor layer is seen through the transparent electrode. Specifically, a plurality of first bus electrodes and a plurality of second bus electrodes extending parallel in a first direction are alternately disposed, and transparent first and second discharge electrodes are provided between the first and second bus electrodes facing each other. The first discharge electrode is electrically connected to the first bus electrode, whilst the second discharge electrode is electrically connected to the second bus electrode. The first and second discharge electrodes may be solid electrodes parallel to the first and second bus electrodes or may have shapes protruding from the first and second bus electrodes. In the first and second discharge electrodes protruding from the first and second bus electrodes for each display cell, edges of these electrodes facing each other are parallel to the first direction and form a parallel slit with constant width (slit width), whereby the discharge occurs across the slit. This slit is hereinafter also referred to as a “discharge slit”.
Although the parallel discharge slit having a straight-line shape as described above is generally used, it is proposed that the discharge slits are formed into various shapes. For example, Japanese Patent Laid-Open Publication No. 2004-71219 (“Patent Document 1”) discloses a shape in which the slit width is gradually varied in each cell. Thereby, high luminance can be obtained without increasing discharge voltage, and uniform discharge can be obtained at every cell.
In a color PDP, phosphor layers with three colors, R, G, and B are provided on three display cells adjacent to one another in the first direction so as to be distinguished respectively. By these three RGB display cells, one color pixel is formed. In view of display quality, it is desirable that color pixels be arranged with approximately the same pitch on a display screen. In each RGB display cell, width (length) of the first direction in which the first and second bus electrodes extend and width (length) of a second direction perpendicular to the first direction become approximately 1:3 ratio. That is, the display cell has an elongated shape extending in the second direction (vertical direction). Therefore, as described above, in the structure where the first and second discharge electrodes extend from the first and second bus electrodes and a discharge slit whose edges opposite to the first and second discharge electrodes are parallel to the first direction is formed, the length of the discharge slit (the length of the facing edges) is short. Therefore, there is the problem in which a discharge region is narrow and sufficient luminance cannot be obtained. Also, there is another problem in which the length of the discharge slit is shorter as the cell is smaller, whereby the discharge voltage is increased.
Japanese Patent Laid-Open Publication No. 7-320644 (“Patent Document 2”), No. 11-86739 (“Patent Document 3”), and No. 2001-110324 (“Patent Document 4”) disclose an electrode shape in which: the first and second discharge electrodes alternately extend like teeth of a comb from the first and second bus electrodes, respectively, and are opposite to the edges extending in the second direction perpendicular to the first direction in which the first and second bus electrodes extend; and the discharge slit extending in the second direction (vertical direction) is formed.
According to the above-mentioned electrode shape (the shape of the vertical discharge slit extending in the second direction), the first and second discharge electrodes face each other over an entire region of the vertically-extending display cell and at the short distance via the discharge slit. Therefore, the voltage for sustaining the discharge can be reduced, so that the discharging region becomes wide and the high luminance is obtained.
To form the vertically-extending discharge slit in the second direction described above, the first discharge electrode and the second discharge electrode have to be extended so as to be spaced a predetermined distance apart from each other in the vertically-extending display cell. Therefore, the shapes of the first and second discharge electrodes become extremely elongated, whereby there is the problem such that disconnection occurs easily. To solve this problem, the above-mentioned Patent Document 2 discloses a structure in which the first and second discharge electrodes are integrally formed with those of the adjacent respective display cells, namely, the discharge electrodes are shared between the adjacent display cells. This structure makes it possible to widen the electrode width and reduce the occurrence of the disconnection.
Also, as described above, the commercially-available conventional AC color PDP mainly has a structure in which two electrodes (X, Y) causing repetitive discharges (sustain discharges) are each constituted by a transparent electrode (discharge electrode) and a metal electrode with a low resistance value (bus electrode) and a gap between these two electrodes (X, Y) for discharge (discharge slit) is approximately parallel to a direction in which the metal electrode extends (first direction). Meanwhile, in the PDP, a square pixel is divided into three portions in the direction in which the metal electrode extends (first direction), and these portions are assigned to cells of three colors, R, G, and B, respectively. Therefore, in one cell, the length (the first-directional distance) of the facing edges of the two electrodes (X, Y) becomes short. Note that the square pixel is a pixel, which is composed of three cells of R, G, and B and has an approximately square shape when viewed from a direction perpendicular to the PDP surface. As the PDP is more finely fabricated, the above tendency becomes more apparent. For this reason, there is proposed the structure (the above-mentioned vertically-extending discharge slit) in which the transparent electrode is drawn to a direction (second direction) perpendicular to the direction in which the metal electrode extends (first direction) and the slit between the two electrodes (X, Y) is provided so as to extend in a direction (second direction) approximately perpendicular to the metal electrode. Such a technique is described in Japanese Patent No. 3144987 (“Patent Document 6”).
The vertically-extending slits disclosed in the Patent Documents 2 to 4 are such that their facing edges are the straight lines parallel to one another. Therefore, if the gap (slit width) between the facing edges is changed due to manufacture error or the like, a firing voltage is also changed, so that there is the problem such that it is difficult to cause a stable discharge. In particular, if the error occurs so that the slit width is varied for each portion of the panel, for example, if the slit width is different between right and left sides, there is the problem such that the display becomes non-uniform.
Moreover, the first and second discharge electrodes are elongated transparent electrodes, so that there is the problem such that the disconnection occurs easily. Furthermore, the transparent electrode is formed of an ITO film or the like. However, if the transparent electrode is an elongated electrode with larger resistance than that of a bus electrode formed of a metal layer, it has a larger voltage drop on a side away from the first and second bus electrodes than that on a near side thereof, so that there is the problem such that no uniform discharge occurs.
As described above, the Patent Document 2 discloses the structure in which the first and second discharge electrodes are shared with the adjacent display cells. However, the problem of the voltage drops at the tips of the first and second discharge electrodes still remains. Moreover, due to manufacturing variations of the gap between the slits, a position for starting the discharge is varied in the cell, so that there is the problem of being recognized as the display non-uniformity on the entire panel.
Still further, in the manufacturing process, a first substrate on which the first and second bus electrodes and the first and second discharge electrodes, etc. are formed and a second substrate on which the third electrodes and the barrier ribs are formed are bonded together. If there is any error in bonding, however, the positions of the barrier ribs with respect to the first and second discharge electrodes are varied. In the structure disclosed in the Patent Document 2 in which the first and second discharge electrodes are shared with the adjacent display cells, if the positions of the barrier ribs with respect to the first and second discharge electrodes are shifted in the first direction, an area ratio between the first and second discharge electrodes is changed in a different direction in the adjacent cell, whereby there arises the problem such that the discharge state differs for each cell. For example, in the AC color PDP, although the display cells adjacent in the first direction are provided with the phosphor layers of three colors, R, G, and B, the problem arises such that a color balance is varied if the discharge states differ between the adjacent display cells.
Furthermore, the AC PDP apparatus is displaced by the repetitive discharge. For this reason, it is desirable to reduce power by decreasing the drive voltage in carrying out the repetitive discharges. This tendency is further required as the number of cells increases by making the display more fine (that is, as the cell width is narrower). Still further, it is desirable to improving the luminance by shortening the drive pulse with respect to the electrodes and reducing a drive time and increase the number of times of discharge. Still further, it is also desirable to improve light-emitting efficiency by reducing a difference between electrical fields created at locations within the vertically-extending discharge space and making density of charge particles in the discharge space uniform.
The present invention aims at solution of the above problems of the vertically-extending slit, and its first object is to achieve a plasma display panel in which a stable discharge is carried out at every display cell. Its second object is to achieve a plasma display panel which improves discharge's uniformity in every display cell by reducing the above occurrence of the disconnection and reducing the voltage drops at the discharge electrodes. Its third object is to achieve a plasma display panel which reduces an influence on a bonding error occurring between the first and second substrates in a manufacturing process. Its fourth object is to achieve a technique for a plasma display panel, which reduces a drive voltage by reducing the electric power in carrying out the repetitive discharges between the two electrodes and improves the luminance by shortening a drive pulse and reducing a drive time and increasing the number of discharge times, and which improves light-emitting efficiency by reducing a difference between electrical fields created at locations within the vertically-extending discharge space and making density of charge particles in the discharge space uniform.
To attain the first object described above, a plasma display panel according to a first aspect of the present invention has a structure in which the width of the vertically-extending slit, that is, a gap between the first and second discharge electrodes, in the display cell is gradually varied in a second direction (vertical direction).
If a minimum value of the gap between the first and second discharge electrodes is close to the paschen minimum defining a discharge start voltage, the discharge start voltage can be effectively reduced.
Furthermore, a gap between facing edges of the first discharge electrode and the second discharge electrode is made so as to be minimum near the center of the display cell and be increased in the second direction (vertical direction) from the vicinity of the center. With this, a discharge starts near the center of the display cell, and then spreads vertically. As such, the discharge spreads from the center of the display cell, and the discharge center position in each display cell is the same. This is desirable for display.
However, the above conditions are not meant to be restrictive. For example, if the gap is made so as to be narrower near the second bus electrode and wider near the first bus electrode, a discharge spreads similarly in each display cell, thereby achieving uniform display.
The shape of the first and second discharge electrodes varying the slit width can be variously modified. For example, at least one of the first and second discharge electrodes has a width that is varied at one end connected to the bus electrode and at the other end. In this case, if the end connected to the bus electrode is narrower in width than the other end, an area of a portion connected to the bus electrode where no discharge occurs is reduced, thereby improving discharge efficiency.
Furthermore, the first aspect in which the slit width is gradually varied can be applied also to a structure disclosed in the Patent Document 2 in which the discharge electrodes are shared between the adjacent display cells.
Next, to attain the second object described above, a plasma display panel according to a second aspect of the present invention includes a first branch bus electrode drawn in a branch shape from a first bus electrode to its facing second bus electrode in the second direction and overlappingly provided so as to electrically make contact with at least part of the first discharge electrode and a second branch bus electrode drawn in a branch shape from a second bus electrode to its facing first bus electrode in the second direction and overlappingly provided so as to electrically make contact with at least part of the second discharge electrode.
The first and second branch bus electrodes are formed of metal layers, tend not to allow a wire break to occur compared with transparent electrodes, have a small resistance, and therefore can reduce a drop in voltage. Since he first and second branch bus electrodes formed of metal layers are opaque, it is desirable that these electrodes be superposed on the barrier ribs so as not to reduce an aperture ratio. Furthermore, in general, the metal layers are in black series, whilst the barrier ribs are in white series. Therefore, by superposing the branch bus electrodes on the barrier ribs, effects can also be achieved such that reflection of external light is reduced and a contrast (light-room contrast) can be improved.
Furthermore, to attain the third object described above, in a plasma display panel according to a third aspect of the present invention, first discharge electrodes for the adjacent display cells are provided adjacently to each other across a barrier rib, and a first connect electrode is provided so as to connect these two first discharge electrodes over the barrier rib. Also, second discharge electrodes for the adjacent display cells are provided adjacently to each other across a barrier rib, and a second connect electrode is provided so as to connect these two second discharge electrodes over the barrier rib. For example, the total width of the first connect electrode and the second connect electrode in the second direction is narrower than the width of each of the first and second discharge electrodes in the second direction.
According to the third aspect of the present invention, since the first and second connect electrodes have a narrow width, even if the position of the barrier rib is displaced in the first direction, variations in area ratio between the electrodes involving a discharge can be reduced compared with the case disclosed in the Patent Document 2 where the discharge electrodes of the adjacent display cells are integrally formed.
Also, even if the structure according to the second aspect in which branch bus electrodes are provided is applied to the third aspect, similar effects can be achieved. Furthermore, the second and third aspects can be combined with the first aspect.
When the second discharge electrode is a scan electrode that causes, together with the third electrode, an address discharge defining a display cell to be lit, an area where the third electrode overlaps with the second discharge electrode is preferably larger than an area where the third electrode overlaps with the second discharge electrode, when viewed from a direction perpendicular to a display surface of the panel.
Still further, the third electrode may not overlap with the first discharge electrode when viewed from the direction perpendicular to the display surface of the panel.
To achieve the above structure, for example, the width of the third electrode is increased at a portion where the third electrode overlaps with the second discharge electrode. Also, when the first discharge electrode and the second discharge electrode are arranged on a straight line in the first direction, the gaps of the third electrodes may be alternately varied.
To achieve uniform display cells, the discharge electrodes of adjacent display cells preferably have an approximately axisymmetric shape with respect to the barrier rib. For example, however, depending on the color of the display cell, the shape of the electrodes and the shape of the slit may be changed.
A dielectric layer on the first substrate is preferably a silicon-dioxide layer with a high density formed through vapor deposition. In this case, the surface of the dielectric layer and the protective layer of the first substrate has asperities in accordance with thicknesses of the first bus electrode, the second bus electrode, the first discharge electrode, and the second discharge electrode. Through a space formed among asperities, exhaustion from a discharge space and injection of discharge gas are performed.
The first and second bus electrodes can be alternately disposed in an order such that first comes the first one, then the second one, the first one, and then the second one, or in an order such that first comes the first one, then the second one, the second one, the first one, the first one, the second one, and then the second one, where two of the first bus electrodes are adjacent to each other on one side and also two of the second bus electrodes are adjacent to each other on one side. In accordance with the arrangement of the first and second bus electrodes, the scheme of drawing the first and second discharge electrode can be variously modified. Accordingly, the scheme of disposing the third electrodes can be variously modified.
Stripe-shaped barrier ribs extending in the second direction (vertical direction) is always required to be provided. In addition, barrier ribs (second barrier ribs) extending in a first direction (horizontal direction) may be provided to form a two-dimensional barrier rib. The barrier ribs in the horizontal direction can be arranged in a manner such that a barrier rib is provided between adjacent bus electrodes or such that two barrier ribs are provided to cover the edges of the bus electrodes. When a barrier rib is provided between adjacent bus electrodes in the horizontal direction, a discharge between the adjacent bus electrodes can be suppressed, thereby making the gap between the bus electrodes narrow. Also, when the barrier ribs are provided so as to cover each of edges of the bus electrodes, the tip of the discharge electrode facing the edge can be extended to the vicinity of the barrier rib in the horizontal direction. However, if the edges are not covered by the barrier ribs in the horizontal direction, a gap between the tip of the discharge electrode and the bus electrode has to be wide so as not to cause a discharge. When a discharge occurs between the bus electrode and the discharge electrode, although no problem arises in terms of operation, light is shielded by the bus electrode, thereby wasting part of emitted light.
Still further, to attain the fourth object described above, a plasma display panel according to a fourth aspect of the present invention has the following structure, particularly regarding edges of two electrodes (first and second discharge electrodes) for discharge at each display cell, the width of the above vertically-extending discharge slit (=a distance between discharge electrode edges), and others. For each cell, a ratio of the width (d2) of the discharge electrode to the width (d1) of the discharge slit in the first direction corresponding to the slit is made smaller than 1 (d2/d1<1), that is, d1>d2. In other words, in the first direction in an area corresponding to the discharge space in each display cell, a relation between the gap (d1) of the slit and the width (d2) of the first and second discharge electrodes positioned on both sides of the slit (however, the width that corresponds to the inside of the cell) is made such that d1 is larger than one-third of the cell breadth area (M) and d2 is smaller than one-third of the cell breadth. The shape of the discharge electrodes is assumed to be, for example, an vertically-extending rectangle with its edges being formed of straight lines.
Here, d1 represents a distance from an edge of one of the two discharge electrodes (X and Y discharge electrode) to an edge of the other of those two discharge electrodes (X and Y discharge electrodes). Also, d2 represents a distance from an edge of one (for example, Y) of the discharge electrodes on a slit side to an opposing edge near a cell boundary (when the discharge electrodes are separately formed between the adjacent cells), or to a position divided by a barrier rib in the horizontal direction (when the discharge electrodes are shared and integrated between the adjacent cells). The position divided by the barrier rib (one end of “d2”) corresponds to, for example, an end of a side surface of the cell of a top surface of the barrier rib in the vertical direction (on a side of making contact with the asperities on the surface of the dielectric layer and the protective layer on the first substrate side), in other words, a position on a top end of the side surface of the cell
That is, the plasma display panel according to the fourth aspect has a group of first metal electrodes and a group of second metal electrodes disposed approximately in parallel on a first substrate; a group of transparent electrodes drawing from the metal electrodes in a direction (second direction) approximately perpendicular to an extending direction (first direction) of the metal electrodes; a dielectric layer and a protective layer covering the two groups of the metal electrodes; a group of third electrodes disposed on a second substrate facing the first substrate and extending in the second direction; barrier ribs approximately in parallel with the group of the third electrodes for division of pixels (display cells) in the first direction; and a phosphor layer applied to the barrier ribs and between the barrier ribs. The transparent electrodes drawn from the first and second metal electrodes face each other across a gap (slit) extending in the second direction. A distance of the gap in the first direction is wider than the width of the transparent electrode in a cell. With this, a difference in electric field in the discharge space can be reduced.
Still further, the above-described first to fourth aspects of the present invention can be applied to, for example, ALIS PDPs disclosed in Japanese Patent No. 2801893 (“Patent Document 5”).
According to the present invention, a plasma display panel in which uniform discharge occurs at all display cells can be manufactured with increased yields. Thus, a high-quality plasma display panel can be achieved at low cost.
Above the discharge electrodes 11b and 12b and the bus electrodes 11a and 12a, a dielectric layer 13 is formed so as to cover these electrodes. This dielectric layer 13 is made of, for example, SiO2 allowing visible light to pass through, and is formed through a vapor deposition scheme. Note that, of the vapor deposition schemes of forming the dielectric layer 13, a CVD method, particularly, a plasma CVD method is suitable and the thickness of the dielectric layer 13 can be made equal to or lower than approximately 10 μm.
Furthermore, on the dielectric layer 13, a protective layer 14 made of MgO or the like is formed. This protective layer 14 has effects of, for example, discharging electrons through ion bombardment to grow a discharge, thereby reducing a discharge voltage and a discharge delay. In this structure, since all electrodes are covered with this protective layer 14, a discharge using the effects of the protective layer is possible even if any one of the electrode groups act as a cathode.
Meanwhile, on a back (second) substrate 2, third (address) electrodes 15 are disposed approximately parallel so as to extend in a second direction (vertical direction) approximately perpendicular to the first direction. The address electrodes 15 are formed of, for example, metal layers. Furthermore, a dielectric layer 16 is formed so as to cover the address electrodes 15.
On the dielectric layer 16, a two-dimensional grid-shaped barrier rib 17 composed of vertical-direction barrier ribs 17a and horizontal-direction barrier ribs 17b is formed. On side and bottom surfaces of grooves formed by the barrier rib 17 and the dielectric layer 16, phosphor layers 18, 19 and 20, which are excited by ultraviolet light occurring at discharge to emit visible light of red, green, and yellow, are applied. The phosphor layers 18, 19, and 20 emit light of, for example, red (R), green (G), and blue (B), respectively.
The first and second substrates 1 and 2 described above are bonded together, air therebetween is exhausted, and discharge gas such as neon (Ne)-xenon (Xe) is injected and sealed, thereby completing the panel.
The X discharge electrodes 11b protrude like teeth of a comb from the X bus electrode 11a to the Y bus electrode 12a, whilst the Y discharge electrodes 12b protrude like teeth of a comb from the Y bus electrode 12a to the X bus electrode 11a forming a pair therewith. Each X discharge electrode 11b extends from and to both sides of the relevant X branch bus electrode 11c. Similarly, each Y discharge electrode 12b extends from and to both sides of the relevant Y branch bus electrode 12c. The X discharge electrodes 11b and the Y discharge electrodes 12b are transparent electrodes. Each X discharge electrode 11b is provided so as to electrically contact with the X bus electrode 11a and the X branch bus electrode 11c, whilst each Y discharge electrode 12b is provided so as to electrically contact with the Y bus electrode 12a and the Y branch bus electrode 12c.
A minimum value of the gap (a value of the gap “d” in the region L2) is set so as to be close to a paschen minimum defining a firing voltage. The distance D1 between the tip of the X discharge electrode 11b and the Y bus electrode 12a and the distance D2 between the tip of the Y discharge electrode 12b and the X bus electrode 11a desirably have values so as not to start the discharge. Therefore, the distances D1 and D2 are desirably larger than the maximum value of the gap “d” between the facing edges of the X discharge electrode 11b and the Y discharge electrode 12b. This is because a portion of light emission through the discharge between a discharge electrode and a bus electrode is prevented from being shielded by the bus electrode serving as a metal layer and from going to waste. Note that if the horizontal barrier rib 17b is extended to the edges of the X and Y bus electrodes 11a and 12a facing the X and Y discharge electrodes 11b and 12b, a discharge at that portion can be prevented, so that the distances D1 and D2 can be further decreased. In this case, the distances D1 and D2 can be equal to or shorter than the gap “d” between the facing edges of the X discharge electrode 11b and the Y discharge electrode 12b.
In the electrode shape of
Referring back to
Further, each address electrode 15 is disposed so as to overlap with the Y discharge electrode 12b but not to overlap with the X discharge electrode 11b. Still further, the address electrode 15 becomes widened at a portion overlapping with the Y discharge electrode 12b so that an area overlapping with the Y discharge electrode 12b becomes large. Therefore, the address electrodes 15 are disposed alternately at narrow gaps and wide gaps. As described further below, an address discharge defining a display cell to emit light is performed between a Y discharge electrode and an address electrode. Therefore, with the above-described structure, the address discharge can be reliably caused to occur and the probability of occurrence of the address discharges can be improved. Also, since the X discharge electrode 11a and the address electrode 15 do not overlap with each other, a capacitance therebetween is reduced, thereby making it possible to be driven easily.
Next, a method of driving the PDP apparatus according to the first embodiment will be described. The PDP apparatus according to the first embodiment uses a driving method similar to that in the conventional technique.
As shown in
In the reset period 21, an operation is performed to make charges in all display cells uniform so as to assist a discharge in the next address period 22. In the address period 22, an address discharge determining a display cell to be turned on is performed. For the address discharge, there are a scheme of forming a charge in a light-emitting cell and a scheme of deleting a charge in a non-light-emitting cell. Here, the scheme of forming a charge in a light-emitting cell is used. In the sustain period 23, a discharge is repeatedly caused to occur in the display cells to be selected in the address period 22, thereby causing the display cells to emit light. Then, with a sustain discharge, the formed charge is deleted.
First, in the reset period, a reset voltage 41 is applied to the X electrode and a write dull wave 51 is applied to the Y electrode, thereby causing a reset discharge to occur in all display cells. With this, a wall discharge is formed near the electrodes. Then, an adjustment voltage 42 is applied to the X electrode and the adjustment dull wave 52 is applied to the Y electrode, thereby reducing the amount of the formed wall discharge to a predetermined amount. With this, a uniform discharge is ready for all display cells irrespectively of the lighting state of the previous subfield. In the reset period, 0 V is applied to the address electrode.
In the address period, with a predetermined voltage 43 being applied to the X electrode, a scan pulse 53 is applied sequentially to the Y electrode with a shifted timing. In response to the scan pulse 53, an address pulse 61 is applied to the address electrode. With this, a discharge occurs from the Y discharge electrode and the address electrode of a display cell in a row (Y bus electrode) applied with the scan pulse 53 and a column (address electrode) applied with the address pulse 61. At this time, a large field occurs between the Y electrode and the X electrode. With a discharge between the Y discharge electrode and the address electrode as a trigger, a discharge occurs between the Y discharge electrode and the X discharge electrode. With this discharge, charges having a polarity in reverse to the polarity of the voltage applied to each electrode are accumulated near the Y discharge electrode and the X discharge electrode. Here, a wall charge having a positive polarity is formed near the Y electrode, whilst a wall charge having a negative polarity is formed near the X electrode. As such, lighting cells are selected on the entire display surface.
In the next sustain period, first sustain pulses 44 and 54 are applied to the X and Y electrodes, respectively. With this, a voltage by the wall charge is superposed at the discharge cells where an address discharge occurred in the address period, thereby causing a sustain discharge for the first time. With this sustain discharge for the first time, the polarities of the charges accumulated near the X discharge electrode and the Y discharge electrode are reversed. Next, pulses 45 and 55 for matching the polarity of the charges are applied, thereby causing a sustain discharge for the second time. Also at this time, the polarities of the wall charges are reversed. Then, sustain pulses 46 and 56 are repeatedly applied with their polarities reversed each time, sustain discharges are repeatedly caused to occur with the polarities of the wall charges repeatedly reversed. To end the sustain period, on-cell delete pulses 47 and 57 are applied to the X and Y electrodes, respectively, to delete or reduce the wall charges only at the display cell where sustain discharges have occurred. When these on-cell delete pulses 47 and 57 are applied, a potential difference between the X discharge electrode and the Y discharge electrode is smaller than that at the time of sustain, and a discharge occurs mainly due to the wall charges. When the amount of wall charges is reduced by the discharges, the occurrence of discharges stops, and the amount of wall charges formed after discharge is small. With this, the wall charges formed by the sustain discharges can be deleted or reduced. Thereafter, modified pulses 48 and 58 are applied to the X and Y electrodes, respectively, and if a large amount of wall charges remains, a weak delete discharge is cause to occur to reduce the wall charges. In the next subfield, a reset period comes back again. Here, during the sustain period, 0 V is applied to the address electrode.
The PDP apparatus according to the first embodiment of the present invention has been described above. The shape of the electrodes, for example, can be variously modified. Modification examples of the shape of the electrodes are described below.
In the shape of the electrodes shown in
In the shape of the electrodes shown in
In the shape of the electrodes shown in
In
In the shape of the electrodes shown in
In the shape of the electrodes shown in
In the shape of the electrodes shown in
In the shape of the electrodes shown in
Also, unlike the first embodiment where the discharge electrodes corresponding to the adjacent display cells are formed as one electrode, with the notches 25 being provided as shown in
As described above, the discharge electrodes are formed on the first substrate 1, the barrier ribs 17a are formed on the second substrate 2, and these first and second substrates 1 and 2 are bonded together. At the time of bonding, a displacement may occur in the horizontal direction, that is, in the direction in which the X and Y bus electrodes 11a and 12a extend.
The modification examples of the shape of the electrodes according to the first embodiment have been described above. Various other modification examples are possible and, needless to say, the features of the modification examples shown in the drawings can be combined.
Also, as shown in
In the PDP according to the second embodiment, the shape of the electrodes for one line is repeated, and various modification examples of the repeated shape are possible. Such modification examples of the repeated shapes are described below.
Also, still another modification example is described with reference to
Furthermore, in an address discharge, areas of the Y discharge electrode and the address electrode that are different from one another (in this drawing, overlapping widths Ar, Ag, and Ab) are changed, thereby equalizing the discharge voltages. For example, if the discharge voltage for G is the highest, then comes that for B, and then that for R, the overlapping widths are set so that Ag>Ab>Ar, thereby equalizing the discharge voltages. Also in this case, it is not required to change all of the slit spaces for three colors, and only one of them may be varied.
As shown in
In an ALIS PDP, a plurality of X bus electrodes and a plurality of Y bus electrodes are alternately disposed, and the number of X bus electrodes is larger by one than the number of Y bus electrodes. From each of the top and bottom X bus electrodes, an X discharge electrode protrudes toward an internal Y bus electrode. From each of the other X bus electrodes and the Y bus electrodes, X and Y discharge electrodes protrude to both sides.
In the shape of the electrodes according to the fifth embodiment, the Y branch bus electrodes 12c protrude from the Y bus electrode 12a to both sides toward the vertical barrier rib 17a so as to overlap with every other vertical barrier rib 17a, and further the Y discharge electrodes 12b protrude from the Y bus electrode 12a to both sides so as to each include the Y branch bus electrode 12c. Similarly, from each of the X bus electrodes 11a vertical adjacent to each other, the X branch bus electrodes 11c and the X discharge electrodes 11b protrude to both sides, and a set of the X branch bus electrode 11c and the X discharge electrode 11b and a set of the Y branch bus electrode 12c and the Y discharge electrode 12b are alternately disposed in the horizontal direction.
The X and Y discharge electrodes 11b and 12b have shapes similar to those of the discharge electrodes according to the second embodiment. Also, the horizontal barrier rib 17b is provided so as to cover the X bus electrode 11a and the Y bus electrode 12a. Therefore, gaps between the tips of the X and Y discharge electrodes 11b and 12b and the X and Y bus electrodes 11a and 12a can be narrowed more than those according to the first embodiment.
In the ALIS technology, an odd-numbered display line is formed between an odd-numbered X bus electrode and an odd-numbered Y bus electrode and between an even-numbered X bus electrode and an even-numbered Y bus electrode, whilst an even-numbered display line is formed between an odd-numbered Y bus electrode and an even-numbered X bus electrode and between an even-numbered Y bus electrode and an odd-numbered X bus electrode. Odd-numbered display lines and even-numbered display lines are alternately subjected to an interlace display in odd fields and even fields.
Also,
The ALIS technology is described in the above-mentioned Patent Document 5, and the driving method is not described in detail herein.
The X and Y discharge electrodes 11b and 12b according to the fifth embodiments have shapes similar to those according to the second embodiment. Therefore, effects similar to those according to the second embodiment can be achieved in an ALIS PDP apparatus.
Next, the structure of a PDP apparatus according to a sixth embodiment of the present invention is described.
In
As a design of distances in the horizontal direction (first direction), consider a breadth (d2) of each discharge electrode (11b, 12b) and a breadth (d1) of each discharge slit in the in-cell areas (C1 to C3). The in-cell breadths of the X and Y discharge electrodes 11b and 12b are identical to each other as d2 (this is the case no displacement in the horizontal direction). d1 represents an edge gap between the facing discharge electrodes (11b, 12b). d2 represents a distance from an edge of the discharge electrode (11b, 12b) on a slit side to an upper end of the vertical barrier rib 17a inside the cell. d1 and d2 are constant irrespectively of the positions in the vertical direction (second direction).
In the structure shown in
The breadths of the two discharge electrodes (11b, 12b) in a cell may be different from each other, but are desirably the same (d2).
In the shape of the electrodes shown in
In
A lower limit (a width required to be allocated at minimum) of d2 described above is now described. In an AC PDP, wall charges are formed near the electrodes. Therefore, an area in which wall charges are formed, that is, a width (d2) in an in-cell portion of the transparent electrode (11b, 12b), has to be at least on the order of 30 μm (the lower limit value). Meanwhile, the vertical barrier rib 17a is formed of the same type of phosphor as that of the dielectric layer 13. Therefore, near a position of the vertical barrier rib 17a making contact with the protective layer 14 (the top surface), an electric field occurs on a side surface of the vertical barrier rib 17a without the protective layer 14. Therefore, part of plus ions 91 are drawn to the vertical barrier rib 17a side and cannot contribute the growth of the discharge. This area not allowing contribution to the discharge depends on the thickness of the dielectric layer 13. When the thickness is 30 μm, the area is approximately 30 μm, and when thickness is 10 μm, the area is approximately 10 μm to 15 μm. In accordance with the thickness of the dielectric layer 13, the length of d2 has to be determined in consideration of the size of the area not allowing contribution to the discharge.
By way of example, when the pitch of the vertical barrier ribs 17a is 200 μm, and the breadth of the top of the vertical barrier rib is 40 μm, assuming that the thickness of the dielectric layer 13 is 10 μm, a distance in the horizontal direction in a discharge area is 160 μm (2×d2+d1=200−40=160 μm). When it is assumed that the gap “d1” between two transparent electrodes is 70 μm, d2 is 45 μm ((160−70)/2=45 μm). This satisfies d1>d2 described above. Also even when it is assumed that an area not contributing to the above discharge is 15 μm, an area having formed thereon wall charges is equal to or longer than 30 μm (45−15=30 μm). This also satisfies d1>d2.
According to the sixth embodiment, the drive voltage can be reduced, the drive time can be shortened, and a difference in electric field can be reduced, thereby improving light-emitting efficiency. In addition, it is possible to achieve effects of reducing the amount of discharge spreading to the second substrate 2 side and mitigating changes of the phosphors (18, 19, 20) with time (these effects can be achieved by d1>d2 mentioned above).
The embodiments and modification examples according to the present invention have been described above. Various other modification examples are possible, and the feature of each of the above-described embodiments and modification examples can be applied to those other embodiments and modification examples.
As has been described in the foregoing, according to the present invention, a drive voltage when driving a PDP with its slits oriented in a vertical direction can be reduced, thereby reducing circuitry cost. With this, a PDP apparatus with a high display quality can be achieved at low cost.
(Note 1) A plasma display panel comprises: a first substrate; and a second substrate disposed opposite said first substrate and forming a discharge space in which a discharge gas is sealed between said first substrate and said second substrate, wherein said first substrate including: a plurality of first bus electrodes and a plurality of second bus electrodes arranged so as to extend in parallel with a first direction and be adjacent to each other on at least one side; a plurality of transparent first discharge electrodes drawn like teeth of a comb from each of said first bus electrodes to said second bus electrodes opposite thereto in a second direction perpendicular to said first direction; a plurality of transparent second discharge electrodes drawn like the teeth of a comb from each of said second bus electrodes to said first bus electrodes opposite thereto in said second direction; and a dielectric layer and a protective layer covering said plurality of first bus electrodes, said plurality of second bus electrodes, said plurality of first discharge electrodes, and said plurality of second discharge electrodes, said second substrate including: a plurality of third electrodes extending in parallel with said second direction; a plurality of barrier ribs extending in parallel with said second direction; and a phosphor layer formed on a surface of said second substrate and side surfaces of said barrier ribs, display cells are formed in portions at which said first bus electrodes and said second bus electrodes face each other and which is separated by said barrier ribs, said first discharge electrodes and said second discharge electrodes are disposed so as to alternately protrude from said first bus electrodes and said second discharge electrodes, and facing edges of said first discharge electrode and said second discharge electrode in each of said display cells extend in said second direction, and a gap between the facing edges of said first discharge electrode and said second discharge electrode in each of said display cells is gradually varied.
(Note 2) In the plasma display panel according to note 1, the gap between the facing edges of said first and second discharge electrodes is minimum near a center of a relevant one of said display cells in the second direction and becomes widened as moving from the center in the second direction.
(Note 3) In the plasma display panel according to note 1, the gap between the facing edges of said first and second discharge electrodes is narrow near said second bus electrode.
(Note 4) In the plasma display panel according to note 1, at least one of said first and second discharge electrodes is such that one ends of said first and second bus electrodes are different in width from that of the ends thereof.
(Note 5) In the plasma display panel according to note 4, the at least one of said first and second discharge electrodes is such that one ends of said first and second bus electrodes are narrower in width than the other ends thereof.
(Note 6) In the plasma display panel according to note 1, a first branch bus electrode drawn from each of said first bus electrodes to said second bus electrodes opposite thereto in said second direction and provided so as to overlap with at least portion of said first connect electrode, and a second branch bus electrode drawn from each of said second bus electrode to said first bus electrodes opposite thereto in said second direction and provided so as to overlap with at least portion of said second connect electrode.
(Note 7) In the plasma display panel according to any one of notes 1 to 6, said second discharge electrodes are scan electrodes that cause, together with said third electrodes, address discharges defining said display cells to be lit, and when viewed from a direction perpendicular to a display surface of the plasma display panel, areas where said third electrodes overlap with said second discharge electrodes are larger than areas where said third electrodes overlap with said first discharge electrodes.
(Note 8) In the plasma display panel according to note 7, said third electrodes are such that portions overlapping with said second discharge electrodes are large in width.
(Note 9) In the plasma display panel according to any one of notes 1 to 6, said third electrode does not overlap with said first discharge electrodes when viewed from a direction perpendicular to a display surface of the panel.
(Note 10) The plasma display panel according to note 1 further comprises: a first connect electrode connecting said first discharge electrode of one of said display cells and the first discharge electrode of another one of said display cells, which is horizontally adjacent to one side of the one of said display cells together across a relevant one of said barrier ribs; and a second connect electrode connecting said second discharge electrode of the one of said display cells and said second discharge electrode of the another one of said display cells, which is horizontally adjacent to the other side of the one of the display cells together across the relevant one of the barrier ribs.
(Note 11) In the plasma display panel according to note 10, at least a portion of said first connect electrode and said second connect electrode is provided near portions at which said first and second discharge electrodes are positioned most closely.
(Note 12) In the plasma display panel according to note 10, total width of said first and second connect electrodes in the second direction is narrower than width of each of said first and second discharge electrodes in the second direction.
(Note 13) In the plasma display panel according to note 10, total width of said first and second connect electrodes in the second direction is equal to width of each of said first and second discharge electrodes in the second direction.
(Note 14) The plasma display panel according to any one of notes 10 to 13 further comprises: a first branch bus electrode drawn from each of said first bus electrodes to said second bus electrodes opposite thereto in said second direction so as to overlap with a relevant one of said barrier ribs and provided so as to overlap with at least portion of said first connect electrode; and a second branch bus electrode drawn from each of said second bus electrode to said first bus electrodes opposite thereto in said second direction so as to overlap with a relevant one of said barrier ribs and provided so as to overlap with at least portion of said second connect electrode.
(Note 15) In the plasma display panel according to any one of notes 10 to 14, said third electrodes do not overlap with the first discharge electrodes when viewed in a direction perpendicular to a display surface of the panel.
(Note 16) In the plasma display panel according to any one of notes 10 to 14, said second discharge electrodes are scan electrodes that cause, together with said third electrodes, address discharges defining said display cells to be lit, and when viewed from a direction perpendicular to a display surface of the plasma display panel, areas where said third electrodes overlap with said second discharge electrodes are larger than areas where said third electrodes overlap with said first discharge electrodes.
(Note 17) In the plasma display panel according to note 16, said third electrodes are such that portions overlapping with the second discharge electrodes are large in width.
(Note 18) In the plasma display panel according to note 16, gaps in arrangement between said plurality of third electrodes are alternately varied.
(Note 19) In the plasma display panel according to any one of notes 10 to 18, said first and second discharge electrodes in the display cells adjacent on both sides of any one of the barrier ribs have approximately axisymmetric shapes with respect to the barrier rib.
(Note 20) In the plasma display panel according to any one of notes 10 to 18, said first discharge electrodes are different in shape from said second discharge electrodes.
(Note 21) In the plasma display panel according to any one of notes 1 to 20, a dielectric layer of said first substrate is a silicon dioxide layer formed through a vapor deposition method
(Note 22) In the plasma display panel according to note 21, surfaces of the dielectric layer and the protective layer of said first substrate have asperities (concavities and convexities) in accordance with thicknesses of said first bus electrode, said second bus electrode, said first discharge electrode, and said second discharge electrode.
(Note 23) The plasma display panel according to any one of notes 1 to 22 further comprises a plurality of second barrier ribs extending in approximately parallel in said first direction, wherein said plurality of barrier ribs and said plurality of second barrier ribs form a two-dimensional barrier rib.
(Note 24) In the plasma display panel according to note 23, said plurality of second barrier ribs are disposed between said first bus electrodes and said second bus electrodes.
(Note 25) In the plasma display panel according to note 23, portions of said first bus electrodes and said second bus electrodes are disposed so as to overlap with said second barrier rib.
(Note 26) In the plasma display panel according to any one of notes 1 to 25, gaps between said first discharge electrodes and said second discharge electrodes are varied in a display cell of a different type in said phosphor layer.
(Note 27) In the plasma display panel according to any one of notes 1 to 25, one of a shape and an arrangement of said third electrode is varied in a display cell of a different type in said phosphor layer.
(Note 28) A plasma display panel comprises: a first substrate; and a second substrate disposed opposite said first substrate and forming a discharge space in which a discharge gas is sealed between said first substrate and said second substrate, wherein said first substrate including: a plurality of first bus electrodes and a plurality of second bus electrodes arranged so as to extend in parallel with a first direction and be adjacent to each other on at least one side; a plurality of transparent first discharge electrodes drawn like teeth of a comb from each of said first bus electrodes to said second bus electrodes opposite thereto in a second direction perpendicular to said first direction; a plurality of transparent second discharge electrodes drawn like the teeth of a comb from each of said second bus electrodes to said first bus electrodes opposite thereto in said second direction; and a dielectric layer and a protective layer covering said plurality of first bus electrodes, said plurality of second bus electrodes, said plurality of first discharge electrodes, and said plurality of second discharge electrodes, said second substrate including: a plurality of third electrodes extending in parallel with said second direction; a plurality of barrier ribs extending in parallel with said second direction; and a phosphor layer formed on a surface of said second substrate and side surfaces of said barrier ribs, display cells are formed in portions at which said first bus electrodes and said second bus electrodes face each other and which is separated by said barrier ribs, said first discharge electrodes and said second discharge electrodes are disposed so as to alternately protrude from said first bus electrodes and said second discharge electrodes, and facing edges of said first discharge electrode and said second discharge electrode in each of said display cells extend in said second direction, and wherein the plasma display panel further comprises: a first branch bus electrode drawn from each of said first bus electrodes to said second bus electrodes opposite thereto in said second direction so as to overlap with a relevant one of said barrier ribs and provided so as to overlap with at least portion of said first connect electrode; and a second branch bus electrode drawn from each of said second bus electrode to said first bus electrodes opposite thereto in said second direction so as to overlap with a relevant one of said barrier ribs and provided so as to overlap with at least portion of said second connect electrode.
(Note 29) A plasma display panel comprises: a first substrate; and a second substrate disposed opposite said first substrate and forming a discharge space in which a discharge gas is sealed between said first substrate and said second substrate, wherein said first substrate including: a plurality of first bus electrodes and a plurality of second bus electrodes arranged so as to extend in parallel with a first direction and be adjacent to each other on at least one side; a plurality of transparent first discharge electrodes drawn like teeth of a comb from each of said first bus electrodes to said second bus electrodes opposite thereto in a second direction perpendicular to said first direction; a plurality of transparent second discharge electrodes drawn like the teeth of a comb from each of said second bus electrodes to said first bus electrodes opposite thereto in said second direction; and a dielectric layer and a protective layer covering said plurality of first bus electrodes, said plurality of second bus electrodes, said plurality of first discharge electrodes, and said plurality of second discharge electrodes, said second substrate including: a plurality of third electrodes extending in parallel with said second direction; a plurality of barrier ribs extending in parallel with said second direction; and a phosphor layer formed on a surface of said second substrate and side surfaces of said barrier ribs, display cells are formed in portions at which said first bus electrodes and said second bus electrodes face each other and which is separated by said barrier ribs, said first discharge electrodes and said second discharge electrodes are disposed so as to alternately protrude from said first bus electrodes and said second discharge electrodes, and facing edges of said first discharge electrode and said second discharge electrode in each of said display cells extend in said second direction, and wherein the plasma display panel further comprises: a first connect electrode connecting said first discharge electrode of one of said display cells and the first discharge electrode of another one of said display cells, which is horizontally adjacent to one side of the one of said display cells together across a relevant one of said barrier ribs; and a second connect electrode connecting said second discharge electrode of the one of said display cells and said second discharge electrode of the another one of said display cells, which is horizontally adjacent to the other side of the one of the display cells together across the relevant one of the barrier ribs.
(Note 30) The plasma display panel according to note 29 further comprises: a first branch bus electrode drawn from each of said first bus electrodes to said second bus electrodes opposite thereto in said second direction so as to overlap with a relevant one of said barrier ribs and provided so as to overlap with at least portion of said first connect electrode; and a second branch bus electrode drawn from each of said second bus electrode to said first bus electrodes opposite thereto in said second direction so as to overlap with a relevant one of said barrier ribs and provided so as to overlap with at least portion of said second connect electrode.
(Note 31) A plasma display apparatus comprises: the plasma display panel according to any one of notes 1 to 30; a first electrode drive circuit for applying a drive signal to said plurality of first bus electrodes; a second electrode drive circuit for applying a drive signal to said plurality of second bus electrodes; and a third electrode drive circuit for applying a drive signal to said plurality of third electrodes.
As described above, according to the present invention, since the drive voltage can be made lower when the slit drives the longitudinal-directional PDP, the manufacture costs of the circuits can be reduced. Thereby, the PDP apparatus with good display quality can be achieved at the low cost.
The present invention is suitable for the PDP, particularly, the highly fine panel.
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