Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2001-04-16
2002-12-17
Saras, Steven (Department: 2675)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S066000, C313S582000
Reexamination Certificate
active
06496167
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plasma display panel of an alternating current discharge type (AC-PDP) for use in a flat display capable of easily realizing a larger display area, such as an output display for a personal computer and a work station as well as a wall-mountable TV, and a method for driving the same.
2. Description of the Related Art
PDPs are classified into a DC type and an AC type on the basis of their structures. The DC-PDP includes electrodes that are exposed in a discharge gas. The AC-PDP includes electrodes that are covered with a dielectric material and not exposed directly in the discharge gas. The AC-PDPs are further classified into a memory operation type PDP which employs a memory function by a charge accumulation effect of the dielectric material, and a refresh operation type PDP which does not use that effect.
FIG. 9
is a cross sectional view showing an example of a general AC-PDP structure. The PDP comprises front glass substrate
10
and back glass substrate
11
to form a certain space therebetween for which there is provided the following structure. A plural of scan electrodes
12
and a plural of common electrodes
13
, both extending in a direction normal to the drawing and being apart from one another at a certain distance are disposed on front substrate
10
. Scan electrodes
12
and common electrodes
13
are covered with insulating layer
15
a
on which there is formed a protection layer
16
consisting of, for example, MgO for protecting insulating layer
15
a
from discharge.
A plural of data electrodes
19
extending from left to right on the drawing are disposed on back substrate
11
so as to intercross scan electrodes
12
and common electrodes
13
at right angles. Data electrodes
19
are covered with insulating layer
15
b
on which there are formed phosphors materials
18
for converting UV rays derived from discharges into visible lights. In order to obtain a color display PDP, each cell may be coated independently with a different phosphors material that has, for example, one of three primary colors of light; red, green and blue (RGB).
FIG. 13
shows an example of the coating of phosphors material on each cell, in which R means red, G green and B blue.
FIG. 13
depicts arrays in which the phosphors materials of RGBRGB . . . are coated in a row direction and the phosphors materials having the identical light emission colors are coated in a column direction.
Partition
17
for defining discharge space
20
and for separating among cells is located between insulating layer
15
a
on front substrate
10
and insulating layer
15
b
on back substrate
11
. A discharge gas is enclosed within discharge space
20
, which consists of a mixed gas selected from He, Ne, Ar, Kr, Xe N
2
, O
2
, CO
2
and the like. At least one of substrates
10
and
11
is transparent.
FIG. 10
is a plan view showing an electrode structure in the color PDP shown in FIG.
9
. At the electrode structure in the color PDP shown in
FIG. 10
, m scan electrodes
12
{S
i
(i=1, 2, . . . , m)} are arranged in a row direction, n data electrodes
19
{D
j
(i=1, 2, . . . , n)} are arranged in a column direction, and thus one cell is provided at a cross point thereof. Common electrodes
13
{C
i
(i=1, 2, . . . , m)} are arranged in the row direction so as to pair with scan electrodes {S
i
}, thus both are in parallel to each other.
A conventional method for driving the PDP constructed as above will be explained bellow.
FIG. 11
is a timing chart showing drive voltage waveforms applied to each of electrodes in the color PDP shown in FIG.
10
.
First, erasing pulses
21
are applied to all the scan electrodes
12
to halt discharge states of cells which have emitted lights till the time shown in FIG.
11
and to bring them into erasing states. The term “erase” herein means an operation of reducing or annihilating wall charges as mentioned later.
Next, priming discharge pulses
22
are applied to common electrodes
13
so that all the cells may emit light by force with discharges, and then priming discharge erasing pulses
23
are applied to scan electrodes
12
in order to erase the priming discharges of all the cells. Priming discharge pulse
22
and priming discharge erasing pulses
23
may ease a write discharge as mentioned later.
After erasing the priming discharge, scan pulses
24
are applied to scan electrodes S
1
-S
m
at different timings, and data pulses
27
are applied to data electrodes
19
(D
1
-D
n
) in accordance with the timing when the corresponding scan pulse
24
is applied. An oblique line depicted in data pulse
27
shows that presence/absence of data pulse
27
has been determined in accordance with presence/absence of the display data. When applying scan pulses
24
, the write discharge may be caused within a discharge space
20
formed between scan electrode
12
and data electrode
19
only in the cells that are provided with data pulses
27
, but not in the cells that are not provided with data pulses
27
.
Positive charges called wall charges are accumulated on insulating layer
15
a
on scan electrodes
12
in the cells where there was caused the write discharge. At the same time, negative wall charges are accumulated on insulating layer
15
b
on data electrodes
19
. Superimposing a positive potential due to the positive wall charges, which are generated on insulating layer
15
a
on scan electrodes
12
, onto a first negative sustaining pulse
25
, which is applied to common electrodes
13
, may cause a first sustaining discharge. When the first sustaining discharge occurs, positive wall charges are accumulated on insulating layer
15
a
on common electrodes
13
, and negative wall charges are accumulated on insulating layer
15
a
on scan electrodes
12
. A second sustaining pulse
26
is superimposed on the, potential difference between the wall charges so as to cause a second sustaining discharge. Thus, the potential difference between the wall charges generated by the sustaining discharges of a n-th time may be superimposed on the sustaining pulse of a (n+1)-th time to continue sustaining discharges. The continuation number of the sustaining discharges may control brightness.
If adjusting the voltages of sustaining pulses
25
and
26
previously at such values that can not cause discharges by only these pulse voltages themselves, the potential due to the wall charges is not present in the cells where there were not caused write discharges before applying the first sustaining pulses
25
. Therefore, the first sustaining discharges can not occur in such cells even when applying the first sustaining pulses
25
, and thus the following sustaining discharges will not occur accordingly. In general, frequencies for applying sustaining pulses
25
and
26
are about 100 kHz, respectively. Waveforms of these pulses are generally rectangular.
In the above explained drive voltage waveforms shown in
FIG. 11
, the duration for applying erasing pulse
21
, priming discharge pulse
22
and priming discharge erasing pulse
23
is called a priming discharge period. The duration for applying scan pulse
24
and data pulse
27
is called a scan period, and the duration for applying sustaining pulses
25
and
26
is called a sustaining period. The priming discharge period, scan period and sustaining period in combination construct a sub-field.
Next, the conventional gradation display method in the PDP will be explained with reference to
FIG. 12. A
field is duration (for example, 1/60 second) for displaying one scene, and may be divided into a plural of sub-fields (for example, 4 sub-fields). Each sub-field has the configuration shown in FIG.
11
and can be controlled independently of other sub-fields with respect to ON/OFF of display. Each sub-field has a different length of sustaining period or the number of sustaining pulses, and a different brightness accordingly. In the case of 4 divided sub-fields as shown in
FIG.
Alphonse Fritz
NEC Corporation
Saras Steven
Sughrue & Mion, PLLC
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