Electric lamp and discharge devices – With gas or vapor – Three or more electrode discharge device
Reexamination Certificate
1998-10-22
2001-04-17
Ramsey, Kenneth J. (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Three or more electrode discharge device
C430S029000, C430S054000, C430S117200, C430S198000, C445S024000
Reexamination Certificate
active
06218779
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for fabricating partitions of a plasma display device and a plasma display device having the partitions fabricated thereby, and more particularly, to a method for fabricating partitions on a rear substrate of a plasma display device using an electrophotography method and a plasma display device having the partitions fabricated thereby.
2. Description of the Related Art
Plasma display devices displaying an image by gas discharge have been known to have superior performances in display capacity, brightness, contrast, a latent image, and a viewing angle, and thus highlighted as a display panel that can replace the conventional CRTs in the future. In the plasma display device, gas discharge is generated between electrodes by direct-current (DC) or alternatingcurrent (AC) voltage applied to the electrodes and then the gas radiates ultraviolet rays so that light is emitted by fluorescent substance excited by the ultraviolet rays. The plasma display device can be classified into an AC type and a DC type according to a discharge mechanism.
FIG. 1
is an exploded perspective view showing the structure of a general AC type plasma display device.
Referring to the drawing, a first electrode
13
a
which is a transparent display electrode and a second electrode
13
b
which is an address electrode are formed between a front glass substrate
11
and a rear glass substrate
12
. The first and second electrodes
13
a
and
13
b
are formed in strips on the inner surfaces of the front and rear glass substrates
11
and
12
, respectively, and are crossed each other when the substrates
11
and
12
are assembled. A dielectric layer
14
and a protective layer
15
are deposited in order on the inner surface of the front glass substrate
11
. The rear glass substrate
12
has a dielectric layer
14
′ formed thereon and partitions
17
are formed on the dielectric layer
14
′. A cell
19
, a space for filling inert gas such as argon (Ar), is formed between the partitions
17
. The partitions
17
are coated with fluorescent material
18
as shown in the drawing.
To operate the plasma display device having the above structure, high voltage, called a trigger voltage, is applied to generate discharge between the electrodes
13
a
and
13
b
. The discharge is generated when cations are stored in the dielectric layer
14
by the trigger voltage. When the trigger voltage exceeds a threshold voltage, the argon gas filling the cell
19
is transformed into a plasma state due to the discharge and a stable discharge state is maintained between the electrodes
13
a
and
13
b
. In the stable discharge state, ultraviolet rays of light emitted during the discharge collides against the fluorescent material
18
to emit light. Accordingly, each pixel formed in an unit of a cell can display an image.
FIG. 2
is a perspective view illustrating a blade coater. The blade coater is one of apparatuses used to fabricate partitions of a plasma display device using a conventional printing method.
Referring to the drawing, a mesh (not shown) is attached on the upper surface of a rear substrate
21
on which the address electrode and the dielectric layer are already formed in the previous process. A blade
22
is installed at the lower portion of a support bar
23
. The support bar
23
can horizontally move above the rear substrate
21
. The blade
22
horizontally moves while pressing material for the partitions in a paste state placed on the mesh attached to the rear substrate
21
so that the partition material can be uniformly coated on the surface of the dielectric layer of the rear substrate
21
.
However, the fabrication of the partition using the blade coater according to the conventional printing method as above causes the following problems.
First, the blade coater printing operation should be repeated several times until the height of the partition having a predetermined width is obtained, during which each printing operation necessitates a drying operation. If the height of a complete partition is about 200 &mgr;m, the printing operation and the drying operation should repeat at least ten times. Thus, the time needed for fabricating the partition gets longer, e.g., one hour or more is required per substrate. Such delay in the fabrication process causes lowering of productivity.
Another problem is that, when the blade presses the partition material in a paste state against the surface of the substrate, the mesh attached on the substrate is deformed due to pressure of the blade. Since the mesh functions to maintain a pattern of the partitions, the deformation of the mesh critically effects the fabrication of the partition according to the designed pattern. That is, the shape of a finally completed partition can be deformed, thereby deteriorating the quality of products.
SUMMARY OF THE INVENTION
To solve the above problems, it is an objective of the present invention to provide a method for fabricating partitions of a plasma display device by an electrophotography method.
It is another objective of the present invention to provide a plasma display device having the partitions fabricated by the electrophotography method.
Accordingly, to achieve the objective of the present invention, there is provided a method for fabricating partitions of a plasma display device comprising the steps of, forming a dielectric layer on the surface of a rear substrate having an address electrode, forming a conductive layer and a photoconductive layer in order on the surface of the dielectric layer, charging the surface of the photoconductive layer, exposing the photoconductive layer covered with a mask of a predetermined pattern to ultraviolet rays so that an electrostatic latent image can be formed on the photoconductive layer, developing the electrostatic latent image by allowing the photoconductive layer, on which the electrostatic latent image is formed, to be in contact with a charged liquid toner layer so that liquid toner can stick to the electrostatic latent image, drying the toner stuck to the electrostatic latent image and absorbing the toner remaining an area other than the electrostatic latent image, repeating three times the steps from the step of charging the surface of the photoconductive layer through to the step of drying and absorbing the toner, and burning the rear substrate where partitions are formed.
It is preferable in the present invention that the dielectric layer is formed of silicate having silicon dioxide as a main ingredient, that the conductive layer is formed by coating an alcoholic solution including ammonium salt on the surface of the dielectric layer and then drying the same, and that the thickness of the conductive layer is formed to be 1 &mgr;m.
It is also preferable in the present invention that the photoconductive layer is formed by coating a composite including a fluorene-based donor, an anthraquinone-based acceptor, a polyacrylate-based binder, and toluene, and then drying the same and that the composition ratio of the fluorene-based donor, the anthraquinone-based acceptor, and the polyacrylate-based binder is at the weight ratio of 5:15:85.
It is further preferable in the present invention that the thickness of the photoconductive layer is between 5-6 &mgr;m, that, in repeating the exposure step three times, a mask having a chromium pattern is used for the first exposing step and the second and third exposing steps are performed without a mask, that the mask is disposed spaced apart about 0.5 mm or less from the surface of the photoconductive layer in the first exposing step, that, in the developing step, liquid toner flowing in a laminar flow state on the surface of an electrode to which current is applied is allowed to be in contact with the photoconductive layer where the electrostatic latent image is formed so that the charged liquid toner is stuck to the electrostatic latent image, and that the distance between the electrode and the photoconductive layer is kept between 0.5-1 mm.
Lowe Hauptman & Gilman & Berner LLP
Ramsey Kenneth J.
Samsung Display Devices Co. Ltd.
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