Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1998-04-28
2001-05-15
Chow, Dennis-Doon (Department: 2675)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
Reexamination Certificate
active
06232935
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an AC surface discharging plasma display panel, and more particularly, to a surface discharging plasma display panel according to an electrode wiring structure and a method for driving the plasma display panel for displaying gray scales.
2. Description of Related Art
A plasma display panel is of a display device for displaying picture data input as an electrical signal by arranging a plurality of discharge tubes in a matrix and by selectively emitting light from them. Methods for driving the plasma display panel are divided into DC driving methods and AC driving methods according to whether the polarity of a pulse voltage applied in order to sustain the discharge changes over time.
FIG. 1A
is a sectional view of a DC opposite surface discharge plasma display panel.
FIGS. 2A and 2B
are respectively a sectional view and perspective view of an AC surface discharge plasma display panel. As shown in the drawings, in both DC and AC types, a discharge space is formed between upper glass plates
1
or
7
and lower glass plates
4
or
12
. In the DC plasma display panel, the flow of electrons is from a negative pole becomes a main energy source for sustaining the discharge, since a scanning electrode
2
and an address electrode
5
are directly exposed to a discharge space
3
. In the AC plasma display panel, a scanning electrode
6
a
and a common electrode
6
b
for sustaining the discharge are electrically separated from a discharge space
10
by a dielectric layer
8
. In the case of the AC plasma display panel, the discharge is sustained by a well known wall charge effect. Namely, the discharge occurs only in a place where the wall charge exists, since a discharge resuming voltage is the sum of a wall voltage and an applied voltage. The discharge is continuously sustained in the place where the discharge first occurred, since the discharge replenishes the wall charge.
Electrode structures are divided into opposite surface discharge structures and surface discharge structures. Namely, the opposite surface discharge electrodes have a structure in which electrodes for generating the discharge are on opposite surfaces of the discharge space. On the other hand, the surface discharge electrodes have a structure in which the electrodes for generating the discharge are both arranged in the same plane, as shown in FIG.
2
A. Electrode structures are also divided into two electrode structures and three electrode structures, according to the number of electrodes installed for realizing a discharge.
FIG. 2B
shows the three electrode surface discharge structure of the plasma display panel in common use. An address electrode
11
is opposite and perpendicular to the two parallel display electrodes, i.e., the scanning electrode
6
a
and the common electrode
6
b
. The discharge spaces are defined by latticed walls. In the structure, the discharge for generating the wall charge is generated in order to select pixels between the address electrode
11
and the scanning electrode
6
a
. Then, the discharge for displaying pictures is maintained for a certain time between the scanning electrode
6
a
and the common electrode
6
b
. A latticed wall
17
defines the discharge spaces and prevents cross talk between adjacent pixels by intercepting light generated by the discharge. The pixels are constructed by forming a plurality of unit structures on a substrate in a matrix and applying a fluorescent material to the unit structures. Such pixels form a plasma display panel. In the plasma display panel in common use, when the discharge is generated in a pixel, ultra-violet rays generated by the discharge excite the fluorescent material coating on the inner wall of the pixel, thus realizing a desired color.
Displaying gray scales is a prerequisite for displaying colors on the plasma display panel. A method of dividing a 1TV field into a plurality of auxiliary fields and time division controlling them is used for realizing gray scales.
FIG. 3
describes the gray scale display method of the AC plasma display panel. This is a 6 bit gray scale display method, in which a TV fields is divided into 6 auxiliary fileds (SF
1
, SF
2
, . . . , SF
6
) and each auxiliary field is divided into address periods (A
1
, A
2
, . . . , A
6
) and discharge sustaining periods (S
1
, S
2
, S
3
, . . . , S
6
). Here, the pixels of the display panel are selected during the address periods (A
1
, A
2
, . . . , A
6
). The gray scales of the pixels selected during the address periods are displayed by the combination of the discharge sustaining periods (S
1
, S
2
, S
3
, . . . , S
6
).
64
gray scales may be displayed by this method. Namely,
64
gray scale levels
0
to
63
are selected from the plasma display panel having
480
scanning lines (Y
1
, Y
2
, . . . , Y
480
). For example, the gray scales are displayed as follows; 0(0T), 1(1T), 2(2T), 3(1T+2T), 4(4T), 5(1T+4T), 6(2T+4T), 7(1T+2T+4T), 8(8T), 9(1T+8T), . . . , 27(1T+2T+8T+16T), . . . , 63(1T+2T+4T+8T+16T+32T).
FIG. 4
shows an example of the electrode wiring structure of the AC plasma display panel in common use. In the structure, there are two sets of parallel electrodes (X and Y electrodes), horizontally facing each other in pairs, and address electrodes
21
, perpendicular to the X and Y electrodes. Here, the X electrodes are common electrodes and are connected in common. The Y electrodes are scanning electrodes. The waveforms of a drive signal for driving the AC plasma display panel having the present wiring structure are shown in FIG.
5
. The address discharge and the sustaining discharge are separately driven by the drive signal. In
FIG. 5
, the waveforms of an address discharge drive signal (A), scanning electrode drive signals (Y
1
, Y
2
, . . . , Y
480
), and a common electrode drive signal(X) are shown. Here, only the signal of a first sub-field (SF
1
) is shown. A
1
and S
1
respectively denote a first address period and a first discharge sustaining period. The address period (A
1
; the first address period) is constructed by the erasing period having a complete erasing period (A
11
), a complete writing period (A
12
), a complete erasing period (A
13
), and an actual address period (A
14
). During the erasing period (A
11
, A
12
, and A
13
), the wall charges generated by a previous discharge are erased in all cells by generating a weak discharge (A
11
), new wall charges are written (A
12
) in all cells, and the new wall charges are partially erased in all cells (A
13
) so that only appropriate wall charges remain in order to correctly display gray scales. Accordingly, the next auxiliary field (SH
2
) operates smoothly. During the address period (A
14
), the wall charge is formed by the scanning electrode in a place on the screen of the plasma display panel selected by a selective discharge by a write pulse between the address electrode and the scanning electrode, and information is written by electric signal. During the discharge sustaining period (S
1
), image information is realized as gray scales by the discharge generated by continuous discharge sustaining pulses. In the discharge sustaining period(S
1
), light is continuously emitted.
However, in the gray scale method of the plasma display panel, the discharge sustaining period (S
1
) is assigned on the basis of an NTSC level of a 6 bit gray scale and amounts to less than 30% of a one frame image display period since the address discharge is driven separately from the sustaining discharge. Therefore, the brightness of the plasma display panel is very low, which is a serious drawback. In the case of being applied to a high definition display device, the discharge sustaining period is further reduced to ½ of the present level, thus the brightness is even more severely lowered. Also, when a larger number of gray scales are made available, the discharge sustaining period is again reduced, thus also reducing the brightness. In order t
Fukushima Masakazu
Ryeom Jeong-duk
Awad Amr
Chow Dennis-Doon
Leydig Voit & Mayer Ltd
Samsung SDI & Co., Ltd.
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