Stock material or miscellaneous articles – Composite – Of quartz or glass
Reexamination Certificate
2000-08-02
2002-05-21
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of quartz or glass
C428S216000, C428S412000, C428S433000, C428S434000, C428S450000, C428S469000, C428S472000, C428S697000, C428S699000, C428S701000, C428S702000, C359S359000, C359S585000
Reexamination Certificate
active
06391462
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical filter for plasma displays, and more particularly, to an optical filter for a plasma display with superior transmittance and reflectivity characteristics.
2. Description of the Related Art
Plasma displays, which generate the visual image by discharging a gas plasma, have been attractive as a substitute for cathode ray tubes (CRTs) due to good display performance thereof, in terms of display capacity, luminance, contrast, reflection image and viewing angle. In plasma displays, application of a direct or current voltage between electrodes creates a discharge of gas plasma therein, resulting in the emission of ultraviolet (UV) light from the gas plasma. The UV emission, in turn, excites adjacent phosphor materials resulting in electromagnetic emission of visual light.
FIG. 1
is an exploded perspective view of the configuration of a common plasma display, and
FIG. 2
is an exploded perspective view of a part of the panel assembly in FIG.
1
.
Referring to
FIG. 1
, the plasma display device includes a case
11
, a cover
15
of the case
11
, and a driving circuit board
12
, a panel assembly
13
and an optical filter
14
, which are accommodated in the case
11
. The panel assembly
13
has a configuration shown in FIG.
2
. Referring to
FIG. 2
, a series of first electrodes
23
a
as transparent display electrodes, a series of second electrodes
23
b
as address electrodes, are arranged between a front glass substrate
21
, and a rear glass substrate
22
. The first electrodes
23
a
and the second electrodes
23
b
are formed on the opposed inner surfaces of the front glass substrate
21
and the rear glass substrate
22
, respectively, perpendicular to each other. A dielectric layer
24
′ is formed over the second electrodes
23
b
on the rear glass substrate
22
and a series of barrier walls
27
are formed on the dielectric layer
24
′ to define cells
29
therebetween. The cells
29
are filled with an inert gas such as argon (Ar). Also, a phosphor
28
is deposited on a predetermined region between the barrier walls
27
, i.e., on a predetermined region of the cells
29
. A dielectric layer
24
is formed over the first electrodes
23
a
and a protective layer
25
is formed thereon.
The driving circuit board
12
of
FIG. 1
includes a variety of electronic parts for applying a voltage to the panel assembly
12
to drive the first and second electrodes
23
a
and
23
b
formed therein, thereby electrically controlling the overall display operation. The optical filter
14
disposed in front of the panel assembly
13
protects the viewer from electromagnetic waves generated by the panel assembly
13
and prevents a reflection of ambient light.
FIG. 3
shows the intersection of the optical filter
14
.
Referring to
FIG. 3
, the known optical filter in the art includes a transparent substrate
31
, an antireflective layer
32
on the front surface of the transparent substrate
31
, for preventing ambient light reflections, and an electromagnetic wave shield
30
on the rear surface thereof.
The antireflective layer
32
is formed of a material, for example, silicon oxide or titanium dioxide, and the electromagnetic wave shield
30
is formed of a material having superior conductivity, for example, silver (Ag). The electromagnetic wave shield
30
is grounded through the cover
15
and to the case
11
. In other words, the electromagnetic waves from the panel assembly
13
are shielded by the electromagnetic shield
30
and grounded through the cover
15
and to the case
11
before they reach the viewer. For this purpose, the electromagnetic wave shield
30
of the optical filter
14
is electrically connected to the cover
15
and the case
11
.
However, the conventional optical filter has the following-disadvantages. Since the reflectivity of the silver layer used as an electromagnetic wave shield is slightly high as a level of 10%, an antireflective layer is further required. In addition, since the optical filter cannot almost shield infrared (IR) light radiated from the panel assembly, an IR shield (not shown) must be interposed between the electromagnetic wave shield and the panel assembly, which avoids a misoperation of the display adopting the optical filter. Also, the optical filter reduces visible light transmittance and in turn contrast characteristic. Poor luminance characteristic of blue phosphor, relative to that of red and green phosphors, increases a need for color correction in the blue visible wavelength range.
SUMMARY OF THE INVENTION
It is an objective of the present invention is to provide an optical filter for plasma displays with antireflective properties and effective electromagnetic wave and infrared (IR) light shielding effects, in which a decrease in reflectivity in the visible wavelength range enhances a contrast characteristic and assures color correction in the blue visible wavelength range.
To achieve the above objective, the present invention provides an optical filter for a plasma display comprising: a transparent substrate; a first transparent dielectric layer formed on the transparent substrate with at least one metal oxide selected from the group consisting of titanium dioxide (TiO
2
), zinc oxide (ZnO), indium oxide (In
2
O
3
), tin oxide (SnO
2
) and cadmium oxide (CdO), or materials obtained by doping the metal oxides with at least one metal selected from the group consisting of indium (In), gallium (Ga), aluminum (Al), tin (Sn) and antimony (Sb); a silver (Ag) layer formed on the first transparent dielectric layer; a metal silver-diffusion barrier layer formed on the silver layer, for suppressing diffusion of silver into the overlaying layer; and a second transparent dielectric layer formed on the metal silver-diffusion barrier layer with at least one metal oxide selected from the group consisting of titanium dioxide (TiO
2
), zinc oxide (ZnO), indium oxide (In
2
O
3
), tin oxide (SnO
2
) and cadmium oxide (CdO), or materials obtained by doping the metal oxides with at least one metal selected from the group consisting of indium (In), gallium (Ga), aluminum (Al), tin (Sn) and antimony (Sb).
REFERENCES:
patent: 4985312 (1991-01-01), Furuya et al.
patent: 5763063 (1998-06-01), Pass et al.
patent: 5834103 (1998-11-01), Bond et al.
patent: 6123986 (2000-09-01), Maschwitz et al.
patent: 93/20256 (1993-10-01), None
Jones Deborah
Lowe Hauptman & Gilman & Berner LLP
McNeil Jennifer
Samsung SDI. Co., Ltd.
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