Electricity: conductors and insulators – Anti-inductive structures – Conductor transposition
Reexamination Certificate
2000-06-14
2002-02-19
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Anti-inductive structures
Conductor transposition
C174S034000, C361S816000, C313S479000
Reexamination Certificate
active
06348653
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plasma display panel (PDP) and in particular to a shield blocking electromagnetic field leakage from the PDP case and simultaneously allowing heat dissipation therethrough.
2. Description of the Related Art
A PDP, as shown in
FIG. 1
, displays an image when gas in its picture cells selectively becomes ionized under a certain voltage and thus generates ultraviolet light which collides with phosphor material
17
coating the walls
13
of the cells that emits visible light. The cells are defined by space between walls
13
, between the front substrate
16
and rear substrate
10
. In order to drive such a PDP high voltage driving signals are applied to electrodes
11
,
14
, and
15
embedded in dielectric layers
18
and
12
on the substrates
16
and
10
and a circuit board
30
, disposed on the outside of the rear substrate as shown in
FIGS. 2 and 3
and having a plurality of electrical/electronic elements such as semiconductor chips, resistors and capacitors, to take a few examples, generates the driving signals. Reference numeral
19
indicates a protective layer.
Because of a concern that electromagnetic field unavoidably generated from such circuits may be harmful to humans exposed to it, an electromagnetic (EM) shield
40
has been placed over the circuit board
30
to prevent EM fields from escaping from a case enclosing the electrical/electronic circuits. However, because electrical circuits also generate substantial heat, the shield must be removed for a proper operation of a device.
Conventionally a plurality of holes
41
were made in an EM shield as shown in FIG.
2
and
FIG. 3
so that the heat can be dissipated through the holes. However, due to the provision of such holes
41
in the shield
40
, sufficient protection against EM field leakage has not been possible.
SUMMARY OF THE INVENTION
It is an objective of the present invention to provide heat dissipation apertures in an EM Field shield and yet prevent leakage of EM through the apertures that would otherwise have happened.
In order to attain the objective, the present invention employs a multi-layered shield, where each of a plurality of preferably metal layers, spaced apart from each other, has apertures that are overlapped by shielding strips of an adjacent layer.
REFERENCES:
patent: 5698818 (1997-12-01), Brench
patent: 6002584 (1999-12-01), Messmer et al.
patent: 6081425 (2000-06-01), Cheng
Leydig , Voit & Mayer, Ltd.
Ngo Hung V
Reichard Dean A.
Samsung SDI & Co., Ltd.
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