Electric lamp and discharge devices – With gas or vapor – Three or more electrode discharge device
Reexamination Certificate
2000-05-12
2001-10-02
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Three or more electrode discharge device
C313S581000
Reexamination Certificate
active
06297590
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field Of The Invention
The present invention relates to a surface discharge plasma display panel (hereinafter referred to as a surface discharge PDP) having a matrix display form, and a method for manufacturing such a plasma display panel.
The surface discharge PDPs are PDPs wherein paired display electrodes defining a primary discharge cell are located adjacent to each other on a single substrate. Since such PDPs can serve adequately as color displays by using phosphors, they are widely used as thin picture display devices for television. And since, in addition, PDPs are the displays that are the most likely to be used as large screen display devices for high-vision pictures, there is, under these circumstances, a demand for PDPs for which the quality of their displays has been improved by increasing resolution and screen size, and by enhancing contrast.
2. Related Arts
FIG. 14
is a cross sectional view of the internal structure of a conventional PDP
90
. A PDP
90
is a surface discharge PDP having a three-electrode structure and a matrix display form, and is categorized as a reflection PDP according to the form of its phosphors arrangements
On the front of a PDP
90
, on an internal surface of a glass substrate
11
, paired display electrodes X and Y are positioned parallel to each other and arranged for each line of a matrix display so that they cause a surface discharge along the surface of the glass substrate
11
. A dielectric layer
17
, for AC driving, is formed to cover the paired display electrodes X and Y and separate them from a discharge space
30
. A protective film
18
is formed on the surface of the dielectric layer
17
by evaporation. The dielectric layer
17
and the protective film
18
are transparent.
Each of the display electrodes X and Y comprises a wide, linear transparent electrode
41
, formed of an ITO thin film, and a narrow, linear bus electrode
42
, formed of a thin metal film (Cr/Cu/Cr). The bus electrode
42
is an auxiliary electrode used to acquire an appropriate conductivity, and is located at the edge of the transparent electrode
41
, away from the plane discharge gap. With such an electrode structure, the blocking of display light can be reduced to the minimum, while the surface discharge area can be expanded to increase the light emission efficiency.
At the rear, an address electrode A is provided on the internal surface of a glass substrate
21
so that it intersects at a right angle the paired display electrodes X and Y. A phosphors layer
28
is formed on and covers the glass substrate
21
, including the upper portion of the address electrode A. A counter discharge between the address electrode A and the display electrode Y controls a condition wherein wall charges are accumulated in the dielectric layer
17
. When the phosphors layer
28
is partially excited by an ultraviolet ray UV that occurs as a result of a surface discharge, it produces visible light emissions having predetermined colors. The visible light emissions that are transmitted through the glass substrate
11
constitute the display light.
A gap S
1
between paired display electrodes X and Y arranged in a line is called a “discharge slit,” and the width wl of the discharge slit S
1
(the width in the direction in which the paired display electrodes X and Y are arranged opposite each other) is so selected that a surface discharge occurs with a drive voltage of
100
to
200
V applied to the display electrodes. A gap S
2
between a line of paired electrodes X and Y and an adjacent line is called a “reverse slit,” and has a width w
2
greater than the width wl of the discharge slit S
1
, that is sufficient to prevent a discharge between the display electrodes X and Y that are arranged on opposite sides of the reverse slit S
2
. Since paired display electrodes X and Y are arranged in a line with a discharge slit S
1
between them, and a line is separated from another line by reverse slits S
2
, each of the lines can be rendered luminous selectively. Therefore, portions of the display screen that correspond to the reverse slits S
2
are non-luminous areas or non-display areas, and the portions that correspond to the display slits S
1
are luminous areas or display areas.
From the front of a conventional panel structure, a phosphors layer
28
in the non-luminescent state is visible through the reverse slits S
2
. And the phosphors layer
28
in the non-luminescent state has a white or light gray color. Therefore, when a conventional display panel is used in an especially bright place, external light is scattered at the phosphors layer
28
and the non-luminescent areas between lines has a whitish color, which results in the deterioration of the contrast of the display.
As a method for increasing the contrast for a color display PDP, proposed are a method for providing a color filter by coating the outer surface of the substrate
11
on the front with a translucent paint that corresponds to the luminous color of a phosphors; a method for arranging on the front face of a PDP a filter that is fabricated separately; and a method for coloring a dielectric layer
17
with colors R, G and B.
It is, however, very difficult to apply coats of individually colored paints at locations corresponding to minute pixels. In case of the separate filter on the front, a gap between the PDP and the filter causes distortion in display images. And in case of the coloring of the dielectric layer
17
, since the tints of coloring agents (pigments) differ, uniformity of permittivity is deteriorated by coloring, and a discharge characteristic is rendered unstable. In addition, positioning is also difficult when coloring a dielectric layer, just as the coating of colored paints.
SUMMARY OF THE INVENTION
It is therefore one object of the present invention to increase display contrast while rendering unnoticeable non-luminous areas between lines.
It is another object of the present invention to provide an optimal structure for forming a light shielding film including black pigment in non-luminous areas between display lines, and a manufacturing method therefor.
According to the present invention, provided is a surface discharge plasma display panel, wherein paired display electrodes extending along display lines are arranged for each display line on the internal surface of a substrate at the front or in the rear, and wherein a light shielding film having a belt shape extending along the display line direction is formed on the internal surface or on the outer surface of the front substrate, so as to overlap each area sandwiched between the adjacent display electrodes.
The area corresponding to a gap (hereinafter referred to as a “reverse slit”) between the display electrodes in adjacent lines on a display screen is a non-luminous area. The light shielding film is arranged to correspond with each non-luminous area. Since the plane pattern of the individual shielding films is formed in a belt shape, a striped shielding pattern is formed for the entire display screen. The shielding film blocks visible light that may be transmitted through the reverse slits. Therefore, the occurrence of a phenomenon where non-luminous areas appear bright due to the external light and a leaking light from display lines is prevented so that the display contrast is increased.
Further according to the present invention, provided is a surface discharge plasma display panel, wherein paired display electrodes are formed for each display line on an internal surface of a front substrate extending along the display lines, and phosphors is deposited on the internal surface of a rear substrate, and wherein a light-shielding film having a darker color than the phosphors with non-luminous condition and having a belt shape extending the display line direction is formed on the internal surface or on the outer surface of the front substrate, so as to overlap each area sandwiched between the adjacent display electrodes.
When viewing the display screen from the front, the phosphors layer is hidden by the
Awaji Noriyuki
Konno Keiichiro
Nakahara Hiroyuki
Nanto Toshiyuki
Sakamoto Naohito
Fujitsu Limited
Greer Burns & Crain Ltd.
Hopper Todd Reed
Patel Nimeshkumar D.
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