Electric lamp and discharge devices – With gas or vapor – With particular gas or vapor
Reexamination Certificate
2002-10-09
2004-06-01
Vu, David (Department: 2821)
Electric lamp and discharge devices
With gas or vapor
With particular gas or vapor
C313S581000, C445S015000, C445S025000
Reexamination Certificate
active
06744208
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a gas discharge light-emitting device, such as a plasma display device, a noble-gas barrier discharge lamp, and an electrodeless discharge lamp, which is used for image display in computer monitors, televisions, and the like, and a manufacturing method for the gas discharge light-emitting device.
BACKGROUND ART
FIG. 10
is a sectional view showing a construction of a panel part of a conventional AC (alternating current) plasma display device.
In the drawing, reference numeral
201
denotes a front glass substrate. A plurality of pairs of display electrode lines
202
are formed in parallel with each other on the front glass substrate
201
. A dielectric glass layer
203
is formed over the display electrode lines
202
. A protective layer
204
made of magnesium oxide is formed on the dielectric glass layer
203
.
Reference numeral
211
denotes a back glass substrate. Address electrode lines
212
are formed on the back glass substrate
211
. A visible light reflective layer
213
is formed over the address electrode lines
212
. Barrier ribs
214
are formed in parallel with each other on the visible light reflective layer
213
, so as to alternate with the address electrode lines
212
. Phosphor layers
215
of the three colors (red phosphor layers
215
R, green phosphor layers
215
G, and blue phosphor layers
215
B) are provided in turn to the gaps between adjacent barrier ribs
214
. When excited by vacuum ultraviolet light of short wavelength (147 nm) which is generated as a result of discharge, the phosphor layers
215
emit light.
Example phosphors of the three colors typically used are given below:
Blue phosphor: BaMgAl
10
O
17
:EU
Green phosphor: Zn
2
SiO
4
:Mn or BaMgAl
10
O
17
:Mn
Red phosphor: YBO
3
:Eu or (Y
x
Gd
1−x
)BO
3
:Eu
Here, a part that is made up of the front glass substrate
201
, the display electrode lines
202
, the dielectric glass layer
203
, and the protective layer
204
is called a front panel, whereas a part that is made up of the back glass substrate
211
, the address electrode lines
212
, the visible light reflective layer
213
, the barrier ribs
214
, and the phosphor layers
215
is called a back panel.
Discharge spaces
220
are formed between the front panel and the back panel. A discharge gas that is a noble gas mixture of a predetermined composition (e.g. a gas mixture of helium (He) and xenon (Xe) or of neon (Ne) and xenon (Xe)) is enclosed in the discharge spaces
220
at a predetermined pressure (about 13.3 kPa (100 Torr) to 80 kPa (600 Torr)).
The illumination principle of this plasma display device is fundamentally the same as that of a fluorescent lamp. Voltages are applied to the electrodes to initiate glow discharge, which causes the discharge gas to generate ultraviolet light This ultraviolet light excites the phosphors to emit light.
A specific example of a manufacturing operation of the plasma display device is given below.
The address electrode lines made of silver are formed on the back glass substrate The visible light reflective layer made of dielectric glass is formed on the back glass substrate on which the address electrode lines have been arranged. The barrier ribs made of glass are formed on the visible light reflective layer at a predetermined pitch.
Phosphor pastes of the three colors that each include a different one of the red, green, and blue phosphors are applied in turn to the channels formed between adjacent barrier ribs. The result is fired at a predetermined temperature (e.g. 500° C.), to form the phosphor layers of the three colors.
Once the phosphor layers have been formed, a low-melting point glass paste is applied to the periphery of the back glass substrate as a sealing material that seals the back glass substrate and the front glass substrate together. The back glass substrate is then subjected to pre-baking at a predetermined temperature (e.g. 350° C.), to remove a resin component and the like from the low-melting point glass paste.
Meanwhile, the display electrode lines, the dielectric glass layer, and the protective layer are formed in this order on the front glass substrate, to form the front panel.
The front panel and the back panel are placed one on top of the other so that the display electrode lines cross over the address electrode lines at right angles and the dielectric glass layer face the barrier ribs. The two panels are heated at a predetermined temperature (e.g. 450° C.) to seal them together (sealing process)
After this, the inside of the panel is evacuated to produce a vacuum while heating at a predetermined temperature (e.g. 350° C.) (evacuation process). The discharge gas is then enclosed at a predetermined pressure (discharge gas filling process).
In the gas discharge light-emitting device manufactured in this way, lower discharge voltages are desirable in order to reduce power consumption. To attain lower discharge voltages, special techniques need to be incorporated in the manufacturing operation.
It is also desirable to improve luminous characteristics. To do so, the phosphor characteristics need to be kept from degrading throughout the whole manufacturing operation. It is generally known that a phosphor suffers thermal degradation during the sealing process. To suppress such thermal degradation, special techniques need be incorporated in the manufacturing operation.
DISCLOSURE OF INVENTION
In view of the above problems, the first object of the present invention is to provide a gas discharge light-emitting device such as a plasma display device that achieves low discharge voltages, and a manufacturing method for the gas discharge light-emitting device.
The second object of the present invention is to provide a gas discharge light-emitting device in which phosphors are protected from thermal degradation during the sealing process of the manufacturing operation and which achieves low discharge voltages, and a manufacturing method for the gas discharge light-emitting device.
The first object can be fulfilled by a gas discharge light-emitting device in which a discharge space filled with a gas medium is formed and which uses a discharge of the gas medium in the discharge space, characterized in that the gas medium includes 0.01% to 1% by volume of water vapor.
With this construction, the water vapor in the gas medium delivers a function of amplifying electrons at the time of discharge. This makes it possible to reduce a voltage which is applied to display electrodes to cause discharge (discharge voltage). Which is to say, when colliding with electrons, the water vapor discharges electrons more easily than a discharge gas such as a noble gas. This electron discharge reaction tends to proceed in a cascade-like manner. As a result, electrons are amplified remarkably.
It was found through experimentation that an optimum value for the water vapor content is in a range of 0.01 to 1% by volume to maximize this water vapor function. If the water vapor content is below 0.01% by volume, the electron amplification function of the water vapor will not be so remarkable. It may appear that the effect of reducing the discharge voltage is more remarkable if the water vapor content is greater. However, if the water vapor content exceeds 1% by volume, the discharge voltage begins to rise. Also, if the water vapor content exceeds 1% by volume when the device is used at a low ambient temperature (below freezing), the water vapor condenses into droplets on the walls that enclose the inner space. This produces undesirable effects.
Here, the gas medium may include at least one noble gas selected from the group consisting of helium, neon, xenon, and argon.
Here, electrodes and phosphors may be provided at least in a periphery of the discharge space, wherein the phosphors (a) are excited by one of ultraviolet light and vacuum ultraviolet light which is generated as a result of the discharge in the discharge space, and (b) emit visible light.
Here, surfaces of the electrodes may be covered with a dielectric.
With this construction, it is possible to
Kado Hiroyuki
Miyashita Kanako
LandOfFree
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