Electric heating – Heating devices – With power supply and voltage or current regulation or...
Reexamination Certificate
2000-07-25
2002-04-23
Paschall, Mark (Department: 3742)
Electric heating
Heating devices
With power supply and voltage or current regulation or...
Reexamination Certificate
active
06376813
ABSTRACT:
FIELD OF INVENTION
The present invention relates to a plasma display panel (PDP), and more specifically, to a plasma display panel for approaching a temperature balance by a eating apparatus formed on a glass panel and the method of the same.
BACKGROUND
A plasma display panel (PDP) is a self-luminous flat display device. Since plasma display panels allow high speed display and make them easy to make large-sized display compared to liquid crystal panels. Thus, they are highly expected to be applicable in the area of a display of television pictures such as display for high definition TV, a monitor of a computer and public relations display units.
The plasma display panel includes a pair of glass panels that are sealed so as to form a chamber. Predetermined ionizable gases are filled in the chamber at a low atmospheric pressure. Typically, the chamber contains neon and/or argon. The anodes are formed on the inside surface of one of the glass panels, and the cathodes are located on the inside surface of the other. An electric potential applied between the pair of glass causes the gases between thereof to ionize, therefore illuminating light. Visible picture may be displayed through upper glass panel by applying potential to a selected anode. The plasma display panel uses a matrix display system.
To display an image, sequential addressing is carried out line by line to select and charge cells that are to emit light. A voltage is used to alter polarity for sustaining a light emitting state. If the voltage is repeatedly applied at a cycle, continuous light emission can be obtained. In the PDP, plasma discharge is caused between anodes and cathodes facing each other in discharge spaces formed between a front glass substrate and a rear glass substrate, and the ultraviolet ray generated by a gas contained in the discharge spaces for displaying. In order to keep the spread of discharge in certain regions for displaying in specified cells, barrier ribs (also called barriers or ribs) are formed and they are typically formed in stripes.
The prior art plasma display has a problem that the temperature levels of the “bright display” area and “dark display” area are different while static pictures are display. Therefore, the thermal distribution is variant. FIG.
1
A and
FIG. 1B
show the thermal distribution of the glass panel
10
consisting of a front glass
10
a
and a rear glass
10
b
. A small bright image (bright display)
12
is present in a dark background (dark display)
14
. As shown in
FIGS. 1A and 1B
, the temperature at the bright image
12
is about 68° C. and the temperature in the non-display area next to the bright image
12
drops to about 40° C. The thermal gradient variation of this area is extremely high and the variation of the temperature is high enough to raise the thermal stress in the glass. The stress may accumulate in the structure of the glass, thus resulting in fracture of the glass. There is a great risk of fracture of the plasma display panel.
The prior art approaches to solve the problem by attaching a thermal spreading element or thermal conductive material, it can be found in U.S Pat. No. 5, 971,566 as shown in FIG.
2
. The thermal spreading element
20
and/or the thermal conductive material
22
is formed on the surface of the glass panel
24
for reducing the heat. The temperature is decreased by the structure, however, the stress is still residual in the glass because the design of the prior art reduces the temperature of the entire surface. The thermal gradient variation problem remains in he structure constructed by the front glass substrate and a rear glass substrate.
FIGS. 2A
,
2
B show that the stress is still too high at the non-display area of the “bright display” area
12
. In these figures, the dash lines indicate the stress distribution, and the solid line represents the temperature distribution. In addition, the cost is too high for making such thermal conductive material
22
on the entire surface.
Thus, there exits a need for an apparatus for plasma display panel that is effective to maintain a smoother thermal gradient across the glass panel.
SUMMARY
An object of the present invention is to provide a heating element on a non-display area of a glass panel for thermal balance. The heating element is turned on or off depending on the temperature of the panel to achieve thermal balance.
The present invention provides a plasma display device which includes a plasma display panel and at least one heating element for heating the plasma display panel. The heating element is formed on a non-display area of the plasma display panel to achieve thermal balance, wherein the heating element adjacent to a bright display area is turned on and the heating element adjacent to a dark display area is turned off. A driving circuit is provided to respond to the temperature of the glass panel to switch the plurality of heating elements. The device may further comprise a sensor to detect a temperature of the plasma display panel.
The present invention also provides a control module for a plasma display device to approach a thermal balance. The control module includes a display panel on which a display area and a non-display area surrounding the display area. At least one heating element is formed on the non-display area for heating the display panel. A driving circuit is coupled to the heating element for switching the heating element. A comparator control circuit is coupled to the driving circuit and responsive to the heating element to send a signal to the driving circuit to control the heating element. The control module further includes a circuit embedded in the control module, wherein the circuit and the heating element construct a Wheatstone Bridge Circuit.
A method for thermal balance for a plasma display device is also disclosed by the present invention. The method includes a step of providing at least one heating element on a non-display area of a glass panel of the plasma display device. Then, a means for heating is provided to heat the glass panel by using the heating element to increase a temperature of the non-display area of the glass plane. Preferably, the temperature of the glass panel is increased between a maximum temperature of a bright display area of the plasma display device and a minimum temperature of the non-display area.
The heating elements adjacent to a bright display area of the glass panel is turned on and the heating elements adjacent to a dark display area of the display panel is turned off.
REFERENCES:
patent: 4520290 (1985-05-01), Cokefair
patent: 4542283 (1985-09-01), Leverenz
patent: 4969849 (1990-11-01), Smith et al.
patent: 5514933 (1996-05-01), Ward et al.
patent: 6130502 (2000-10-01), Kobayashi et al.
Li Chien-Hsing
Tsai Tzeng-Shii
Yu-Ming Huang
Acer Display Technology Inc.
Blakely , Sokoloff, Taylor & Zafman LLP
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