Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of...
Reexamination Certificate
1999-04-26
2001-09-18
Nelms, David (Department: 2818)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
C438S763000, C501S020000
Reexamination Certificate
active
06291362
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a plasma display device, and more particularly to a method of fabricating a dielectric layer for a plasma display device wherein the dielectric layer is formed by depositing dielectric powder on a substrate directly. Also, this invention is directed to a method of fabricating a fluorescent film wherein the fluorescent film is formed by depositing fluorescent powder on a substrate directly.
2. Description of the Related Art
A conventional alternative current system plasma display panel (hereinafter, AC-system PDP) includes a lower glass substrate
10
mounted with an address electrode
12
, and an upper glass substrate
20
mounted with a transparent electrode pair
22
, as shown in
FIG. 1. A
lower dielectric thick film
14
with a predetermined thickness for forming a wall charge and a barrier rib
16
for dividing discharge cells are sequentially formed on the lower glass substrate
10
mounted with the address electrode
12
. A fluorescent film
18
is coated on the surface of the lower dielectric thick film
14
and the wall surface of the barrier rib
16
into a predetermined thickness. The fluorescent film
18
is radiated by an ultraviolet generated during the plasma discharge to generate a visible light. Meanwhile, an upper dielectric thick film
24
and a protective film
26
are sequentially formed on the bottom surface of the upper glass substrate
20
mounted with the transparent electrode pair
22
. The upper dielectric thick film
24
forms a wall charge like the lower dielectric thick film
14
, and the protective film
26
protects the upper dielectric thick film
24
from an impact of gas ions during the plasma discharge. Such an AC-system PDP has discharge cells formed by isolating the lower and upper glass substrates
10
and
20
through the barrier rib
16
. He+Xe mixture gas or Ne+Xe mixture gas is sealed into the discharge cells.
All the lower and upper dielectric thick films
14
and
24
used in such an AC-system PDP must have a capability of performing a function of anti-diffusion film as well as improving the discharge sustenance and the radiation efficiency. In order to perform a function of anti-diffusion film, all the lower and upper dielectric thick films
14
and
24
must have a high thermal stability, a high calcining temperature and a dense organization. Also, in order to improve the radiation efficiency, that is, in order to improve the brightness, the lower glass substrate
14
must have a high reflective coefficient in such a manner to reflect a visible light back-scattered from the fluorescent film
18
while the upper glass substrate
24
must a high transmissivity in such a manner to transmit visible lights from the fluorescent film
18
as much as possible. Furthermore, in order to improve the discharge sustenance, the lower dielectric thick film
14
must have a low dielectric constant while the upper dielectric thick film
24
must have a high dielectric constant. For instance, it is required that the upper dielectric thick film
24
have a dielectric constant more than “13” and the lower dielectric thick film
14
have a dielectric constant less than “10”.
The dielectric thick films
14
and
24
are formed by a process as shown in FIG.
2
. In step
30
, non-crystallized glass powder is prepared. In order to prepare the non-crystallized glass powder, raw materials of a SiO
2
—ZnO—B
2
O
3
group non-crystallized glass or a P
2
O
5
—ZnO—BaO group non-crystallized glass are mixed at a desired component ratio. The raw materials of the mixed SiO
2
—ZnO—B
2
O
3
group non-crystallized glass or a P
2
O
5
—ZnO—BaO group non-crystallized glass are heated for about 5 hours into a temperature of about 1100° C. at a melting furnace to be melted. In the period of melting the raw materials of the non-crystallized glass, the raw materials is stirred two or three times to produce a uniform liquid-state non-crystallized glass. The liquid-state non-crystallized glass is suddenly cooled to thereby have a dense organization and to produce glass cullets with minute cracks. The cullets are milled for a desired time (e.g., 16 hours) by the ball milling technique and thereafter passes through #170 and #270 sievers sequentially, thereby making non-crystallized powder having a particle size of about 6 &mgr;m. In step
32
, such non-crystallized glass powder is mixed with filler powder at a predetermined component ratio. The non-crystallized glass powder and the filler powder having the predetermined component ratio is mixed during a desired time (e.g., 10 hours) by means of a tumbling mixer. In step
34
, the non-crystallized glass powder and the filler powder mixed in this manner is mixed with an organic vehicle at a predetermined component ratio to thereby produce a paste. Herein, a mixture of butyl-carbitol-acetate(ICA), butyl-carbitol(BC) and ethyl-cellulose(EC) with the organic vehicle at a desired ratio is used as the organic vehicle. A viscosity of the paste is varied in accordance with a quantity of EC to have an influence on the rheology and sintering characteristic. Subsequently, in step
36
, the paste is coated on the glass substrate
10
or
20
at a uniform thickness. The coating of the paste is carried out by a repetitive screen printing. In the screen printing technique, as shown in
FIG. 3A
, a screen
40
is installed at the upper portion of the glass substrate
10
or
20
, and a paste
42
is disposed on one edge of the screen
40
. The paste
42
is pushed into other edge of the screen
40
in such a manner to be coated on the glass substrate
10
or
20
at a constant thickness as shown in FIG.
3
B. Then, the paste
42
is again put on one edge of the screen
40
as shown in FIG.
3
C. The paste
42
is further pushed into other edge of the screen
40
by a squeezer such that it is again coated on the glass substrate
10
or
20
as shown in FIG.
3
D. By such a repetitive screen printing, the paste
42
is coated on the glass substrate
10
or
20
at a desired thickness (e.g., 15 to 20 &mgr;m). The glass substrate
10
or
20
coated with the paste
42
in this manner is dried during a desired time (e.g., about 20 to 30 minutes) at a temperature of 350 to 400° C. within a dry oven (not shown) at the atmosphere. At this time, an organic vehicle included in the paste is completely burned out. After the organic vehicle is completely eliminated, the glass substrate
10
or
20
is heated into the crystallization temperature during a desired time to sinter a non-crystallized glass included in the paste
42
. Consequently, the glass substrate
10
or
20
is cooled during a desired time(e.g., about 40 minutes) at a cooling time of 6° C./min to form a dielectric thick film
14
or
24
on the glass substrate
10
or
20
. Herein, the paste
42
, that is, a sintering temperature of the dielectric thick film
14
or
24
is set to less than 600° C. so as to minimize a thermal deformation of the glass substrate,
10
or
20
.
Such a screen printing technique complicates a dielectric thick film fabricating method because it needs a forming process and a sintering process of the paste. The calcining temperature is too low at the time of sintering the paste, the dielectric thick film is not eliminated completely to have a non-uniform surface. Due to this, the dielectric thick film absorbs or scatters a visible light to have a low light transmissivity. On the contrary, when the calcining temperature is too high, the surface of the dielectric thick film is damaged. As a result, a bonding between the dielectric thick film and the protective film is not only weakened, but also a characteristic of the protective film is deteriorated. The fluorescent film included in the PDP along with the dielectric thick film also is formed by the paste producing process, the screen printing process and the sintering process in similarity to the dielectric thick film. Due to this, the fluorescent film fabricating method also is complicated like the dielectric thick fi
Dang Phuc T.
Fleshner & Kim LLP
LG Electronics Inc.
Nelms David
LandOfFree
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