Electric lamp and discharge devices – With gas or vapor – Three or more electrode discharge device
Reexamination Certificate
2002-09-30
2004-07-27
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Three or more electrode discharge device
C313S584000, C313S586000, C313S587000
Reexamination Certificate
active
06768262
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plasma display panel, and more particularly, to a plasma display panel capable of improving the contrast using a black matrix.
2. Description of the Related Art
In general, a plasma display panel (hereafter, referred to as PDP) is a display device that uses the visible rays generated when vacuum ultraviolet rays generated by gas discharge excite phosphor.
The PDP is thinner in thickness and lighter in weight than the cathode ray tubes (CRTs) that have been usually employed as display devices. The PDP has an advantage in that a high definition and large-sized screen can be realized.
The PDP that has such advantages described above includes many discharge cells arranged in matrix fashion and each of the discharge cells works as one pixel of a screen.
FIG. 1
illustrates the structure of three-electrode AC surface discharge type PDP in the related art. Even though
FIG. 1
depicts one discharge cell
1
for the convenience of explanation, a PDP has generally many millions of the discharge cells
1
shown in the
FIG. 1
in matrix fashion.
Referring to
FIG. 1
, a three-electrode AC surface discharge type PDP in the related art includes first electrodes
12
Y and second electrodes
12
Z formed on a front substrate
10
and address electrodes
20
X formed on a rear substrate
18
.
A front dielectric layer
14
and a protective layer
16
are laminated on the front substrate
10
that has the first electrodes
12
Y and the second electrodes
12
Z arranged in parallel. Wall charge generated during plasma discharge is stored on the front dielectric layer
14
. The front dielectric layer
14
is designed to have a thickness within 30 &mgr;m to 45 &mgr;m. The protective layer
16
protects the front dielectric layer
14
from damages caused by sputtering during plasma discharge and also improves the second electrons emission efficiency. The protective layer
16
is usually made of magnesium oxide (MgO).
A rear dielectric layer
22
and barrier ribs
24
are formed on the rear substrate
18
that has the address electrodes
20
X formed thereon. A phosphor layer
26
is coated on the surfaces of the rear dielectric layer
22
and the barrier ribs
24
. The address electrodes
20
X is formed in the direction to cross over the first electrodes
12
Y and the second electrodes
12
Z. The barrier ribs
24
are formed in parallel with the address electrodes
20
X so as to prevent the ultraviolet rays and the visible rays generated by the plasma discharge from leaking into the neighboring discharge cells
1
.
The phosphor layer
26
is excited by the ultraviolet rays generated during the plasma discharge so as to generate one of visible rays of red, green and blue colors. The inert gas for discharge is injected into discharge spaces prepared between the front substrate
10
/the rear substrate
18
and the barrier ribs
24
. As shown in
FIG. 2
, a black matrix is formed between the first electrode
12
Y and the second electrode
12
Z which are respectively formed in the neighboring discharge cells
1
.
FIG. 2
illustrates the front substrate
10
of PDP shown in FIG.
1
. As shown in
FIG. 2
, a black matrix
30
is formed between a first electrodes group including the electrodes
12
Y
1
and the second electrodes
12
Z
1
and a second electrodes group including the electrodes
12
Y
2
and the second electrodes
12
Z
2
that are different from electrodes
12
Y
1
and the second electrodes
12
Z
1
respectively. More particularly, the black matrix
30
is formed on the areas from the external edge
11
of the second electrodes
12
Z
1
included in the first electrodes group to the external edge
13
of the first electrodes
12
Y
2
included in the second electrodes group.
In this AC surface discharge type PDP, one frame is divided into a few subfields each of which is different from others in the number of discharge times so as to display the gray levels of images. Each of the subfields is divided into a reset period for generating a uniform discharge, an address period for selecting a discharge cell, and a sustain period for displaying gray levels according to the number of discharge times. For example, to display an image in 256 gray levels, the frame period (16.67 ms) corresponding to one 60th second is divided into eight subfields.
Each of the eight subfields is divided into the reset period, the address period and a sustain period. The reset period of each subfield is the same as the address period in length while the sustain period increases at each subfield at the ratio of 2
n
(n=0, 1, 2, 3, 4, 5, 6 and 7). In this way, the sustain period of each field is different from that of other fields, and hence the gray levels of the image can be displayed.
In the reset period, reset pulses are applied to the first electrodes
12
Y to cause reset discharge. In the address period, scan pulses are applied to the first electrodes
12
Y and data pulses are applied to the address electrodes
20
X to cause address discharge between two electrodes
12
Y and
20
X. The wall charge is created on the front dielectric layer
14
and the rear dielectric layer
22
during the address discharge. In the sustain period, AC signals that are alternatively applied to the first electrodes
12
Y and the second electrodes
12
Z cause sustain discharge between two electrodes
12
Y and
12
Z.
In such a PDP of the related art, the contrast is degenerated due to the reset discharge caused in the reset period and the address discharge caused in the address discharge. In other words, the light generated by the reset discharge and the address discharge lowers darkroom contrast since the reset discharge and the address discharge do not contribute to the brightness of the PDP.
In order to improve the contrast, as shown in
FIG. 3
, a black matrix
32
is formed on the areas from the external edge
15
of the second electrodes
12
Z
1
included in the first electrodes group to the external edge
17
of the first electrodes
12
Y
2
included in the second electrodes group. The black matrix
32
shields the light generated by the reset discharge and the address discharge to improve the contrast. Since the light generated by the first electrodes
12
Y
2
during the reset discharge and the address discharge does not contribute to the brightness, the black matrix
32
shields the light to improve the contrast.
However, the black matrix
32
to improve the contrast also shields the light generated by the sustain discharge that contributes to the brightness. The sustain pulses are applied to the first electrodes
12
Y
2
. It is desired that the light generated by the sustain discharge should not be shielded since it contributes to the brightness. In case a black matrix
32
is formed on the areas from the external edge
15
of the second electrodes
12
Z
1
included in the first electrodes group to the external edge
17
of the first electrodes
12
Y
2
included in the second electrodes group, the black matrix
32
also shields the light generated by the sustain discharge so that the brightness degenerates and also the light emission efficiency and the display quality deteriorate.
SUMMARY OF THE INVENTION
An object of the invention is to at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.
Accordingly, it is an object of the present invention to provide a plasma display panel capable of enhancing the contrast by overlapping a first electrode to which scan pulses are applied among a plurality of electrodes with a black matrix.
These and other objects and advantages of the invention are achieved by providing a plasma display panel which includes: a first electrodes group including a first electrode formed on a front substrate, a second electrode formed in parallel with and near to the first electrode, and a third electrode formed in parallel with and spaced widely from the second electrode; a second electrodes group formed adjacent to the first electrodes group, and including first to
Ahn Young Joon
Kang Seong Ho
Fleshner & Kim LLP
LG Electronics Inc.
Patel Nimeshkumar D.
Santiago Mariceli
LandOfFree
Plasma display panel does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Plasma display panel, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Plasma display panel will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3250601