Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Forming nonplanar surface
Reexamination Certificate
2000-03-24
2003-01-28
Huff, Mark F. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Forming nonplanar surface
C430S322000, C430S325000, C430S311000, C430S317000, C216S041000, C216S080000, C216S099000, C216S100000
Reexamination Certificate
active
06511793
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing a microstructure such as a barrier lib or a spacer formed at an internal space between two flat panels constructing a flat panel display and, in particular, to a method of manufacturing a microstructure using a photosensitive glass substrate.
2. Description of the Background Art
Recently, flat panel displays (FPD) playing a major role in a man-machine interface, such as liquid crystal displays (LCD), field emission displays (FDD), plasma display panels (PDP), plasma address liquid crystal displays(PALC) are having been actively developed. Each of the above-described flat panel displays commonly includes two flat panels, each being arranged at a certain distance from each other, and a plurality of pixels formed between the two flat panels. In addition, the displays have something in common in that an internal space of the display formed between the two flat panels has to maintain a lower pressure than an external air pressure and the size of the internal spacer has to be maintained constant. For this purpose, it is necessary to manufacture a microstructure member such as a barrier lib or a spacer between the two flat panels, in order to prevent a damage to the panels due to a difference between the pressure in the internal space of the flat panel display and the external air pressure, and maintain the thickness of the internal space constant.
For a method of manufacturing a barrier lib applied to the manufacture of PDP and PALC in this microstructure member, screen printing method, sand blasting method, molding method, etc. are proposed. However, there have been many problems in those methods.
In case of the screen printing method, there is a problem that it takes much time for manufacturing a barrier lib because the method requires a process of repeating printing and drying several times, and it is difficult to form a high definition barrier lib because the shape of the barrier lib is distorted when a screen alignment is not performed well.
In case of the sand blasting method, there is a problem that since a barrier lib is manufactured by abrading the panel using polishing particles, the material of the panel is wasted and accordingly the manufacturing cost is high, and since the panel is shocked by the polishing particles, it is likely to lead a damage to the panel.
The molding method is forming a barrier lib by putting a mold on a semi-solid phased film, a material for the barrier lib, or a paste and applying a uniform pressure to the mold. However, there is a problem that it is difficult to manufacture a barrier lib of an uniform height and separate the mold and the barrier lib because it is difficult to apply a uniform pressure to the mold.
Besides, LIGA (Lithography, Electroplating and Molding), silicon anistrophic etching, photosensitive glass substrate etching, etc. are newly proposed as another method of manufacturing a microstructure.
However, there is a problem that the LIGA requires a high-priced equipment because X-rays has to be generated by the method.
In addition, the silicon anistrophic etching is a method of performing anistrophic etching after forming a mask pattern on a silicon single crystal substrate. However, there is a problem that since it is difficult to etch a large area at an uniform depth, it is difficult to manufacture a microstructure of an uniform height, and since the price of the silicon single crystal substrate is very high, the manufacturing cost is high.
The photosensitive glass substrate etching among the conventional methods of manufacturing a microstructure will now be described in brief.
Firstly, as illustrated in
FIG. 1A
, a photosensitive glass substrate
2
is prepared. The photosensitive glass substrate
2
is mainly composed of SiO
2
and Li
2
O, including a small amount of CeO
2
and Al
2
O
3
and a small amount of photosensitive metals such as Au, Ag and Cu. Besides, other oxides may be included as the needs arise.
Next, as illustrated in
FIG. 1B
, a mask pattern
4
is put on the photosensitive glass substrate
2
, and ultraviolet rays are irradiated on a portion not covered with the mask pattern
4
. Generally, the energy for irradiating ultraviolet rays on a photosensitive glass substrate
2
with a thickness of 1 mm is approximately 2J/cm
2
when the wavelength of the ultraviolet rays is 310 nm.
In the glass substrate
2
exposed to ultraviolet rays for a predetermined time, as trivalent Ce ions are changed into tetravalent Ce ions at an exposed portion, electrons are released into the glass substrate
2
.
Next, the mask pattern
4
on the glass substrate
2
is removed and the glass substrate
2
is heat-treated at a temperature of 350° C. for about 30 minutes. The electrons react with photosensitive metal ions at the exposed portion of the glass substrate
2
to thereby deposit metal elements.
Next, the glass substrate
2
from which the metal elements are deposited is heat-treated at a temperature of 570° C. for 2~3 hours. Then, as illustrated in
FIG. 1C
, crystal phases such as SiO
2
, Li
2
O, etc. are formed around metals using the metals as the core at the exposed portion (D
1
) of the photosensitive glass substrate
2
. In other words, the exposed portion (D
1
) is a mixed structure of amorphous and crystal phases, and the percentage of crystal phases is about 25%. Meanwhile, an unexposed portion has an amorphous structure.
Next, when the glass substrate
2
is dipped in an aqueous solution including HF for a predetermined time, the exposed portion (D
1
) having the mixed structure of crystal phases is dissolved and then removed to thereby have a structure in FIG.
1
D.
The above-described photosensitive glass substrate etching is a method of removing the exposed portion using the etching selectivity between the crystallized exposed portion and the unexposed portion, and, in particular, the method of removing the exposed portion thus described is referred to as positive etching. The above positive photosensitive glass substrate etching is widely utilized in forming a barrier lib of FED, PDP and PALC and an exposure of an inkjet head. It is also possible to form a hole with a diameter of 60 &mgr;m on a glass substrate with a thickness of 200 &mgr;m using the positive photosensitive glass substrate etching.
However, in the positive photosensitive glass substrate etching, there is a disadvantage that it is difficult to obtain a microstructure of a desired shape if the deposition degree of crystal phases at the exposed portion is not sufficient, so that heat treatment and etching have to be repeated in order to deposit sufficient crystal phases, thus making the process complicated and requiring a lot of time, although the method has an advantage that it is less expensive. That is, in a case where the percentage of crystal phases is about 25% in the structure of the exposed portion, the etching selectivity between the. exposed portion and the unexposed portion is not high, so that the exposed portion is not etched well and thus residuals remain at the exposed portion. Therefore, in case of manufacturing a microstructure having a high aspect ratio, there arises a problem that it is difficult to form a hole of a uniform size and the shape of a side wall of the microstructure is distorted.
Accordingly, there arises a problem that it is difficult to manufacture a microstructure with high reliability. In addition, the thermal expansive coefficient of a microstructure using a photosensitive glass substrate in the conventional art is about 7.5×10
−6
. Generally, the microstructure is adhered to the substrate or a dielectric layer having a natural thermal expansive coefficient. However, the thermal expansive coefficient of glass most frequently used as a substrate for a flat panel display is 8.3~8.6×10
−6
in general. In case of a metal substrate frequently used as a material replacing the glass recently has a higher thermal expansive coefficient. Therefore, in a case where the difference in th
Cho Soo-Je
Ryu Byung-Gil
Chacko-Davis Daborah
Fleshner & Kim LLP
Huff Mark F.
LG Electronics Inc.
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