Coating processes – Electrical product produced – Transparent base
Reexamination Certificate
2001-02-13
2002-09-03
Talbot, B K (Department: 1762)
Coating processes
Electrical product produced
Transparent base
C427S164000, C427S307000, C427S600000, C349S123000, C134S001300, C134S002000, C134S006000, C134S033000
Reexamination Certificate
active
06444255
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a method for producing a liquid crystal display and a method for cleaning a substrate.
2. Description of the Prior Art
Liquid crystal displays are thin and light and have low electric power consumption so as to be widely used for note-type and subnote-type personal computers. With the improvement of performance of personal computers, it has been required to increase the display capacity and display area of such liquid crystal displays and to improve the picture quality thereof. With the requirement of the improvement of picture quality, the deterioration of picture quality has been caused by slight scratch defects and chrominance non-uniformity produced during the manufacturing process. In order to prevent the occurrence of such scratch defects and chrominance non-uniformity, fine contaminations (particles) as well as organic films adhered to substrates must be removed in cleaning steps which are carried out as pretreatment steps in respective processes.
Referring to
FIGS. 8 and 9
, a conventional cleaning step for use in a method for producing a liquid crystal display will be described blow.
FIG. 8
shows a step of cleaning a substrate before forming an alignment layer, and
FIG. 9
shows a step of cleaning a substrate after forming an alignment layer. When the substrate is e.g., an array substrate, i.e., a transparent substrate on which a plurality of scanning lines intersect a plurality of signal lines and wherein thin film transistors (each of which will be hereinafter referred to as a “TFT”) serving as switching elements are arranged on the respective intersecting portions, some of the TFTs being connected to pixel electrodes, the term “substrate before forming the alignment layer” means a substrate on which pixel elements are formed. When the substrate is a counter substrate facing the array substrate, e.g., a color filter substrate (which will be also hereinafter referred to as a “CF substrate”), i.e., a transparent substrate, on which grid-like shading films of a black organic resin are arranged and a plurality of colors of colored layers of red, blue and green are arranged in the form of stripes so as to fill in the spaces between the grid and wherein a common electrode of ITO (indium tin oxide) is formed on the whole surface of the colored layers, the term “substrate before forming the alignment layer” means a substrate on which at least a common electrode is formed.
Referring to
FIG. 8
again, a step of cleaning a substrate before forming an alignment layer will be described. First, such a substrate
2
is fed to a brush cleaning unit
120
by means of transfer rollers
111
. Then, a cleaning solution is sprayed on the substrate
2
from nozzles
125
. This cleaning solution is prepared by mixing a surface active agent with a pure water so as to have a predetermined concentration. The cleaning solution is prepared in a mixing tank
110
and pumped out by means of a pump
115
to be supplied to the nozzles
125
.
The surface of the substrate
2
, on which the cleaning solution has been sprayed, is rubbed by brushes
123
, so that relatively large contaminations (particles) are removed from the substrate
2
to clean the substrate
2
. Therefore, the waste water discharged from the brush cleaning unit
120
contains a surface active agent of high concentration.
Then, the substrate
2
, which has been cleaned by the brushes
123
, is fed to a pure water jet unit
130
by means of transfer rollers
111
. Then, a high pressure pure water is sprayed on the substrate
2
from jet nozzles
135
. Thus, the surface active agent on the substrate
2
is replaced with a pure water, and particles are removed by the high pressure pure water. Furthermore, the high pressure pure water is pumped out of a pure water storage tank (not shown) by means of a high pressure pump
133
to be supplied to the jet nozzles
135
, and jetted from the jet nozzles
135
as a jet flow.
Then, the substrate
2
is fed to a shower unit
140
by means of transfer rollers
111
. Then, a pure water is sprayed on the substrate
2
from shower nozzles
143
to wash the surface active agent and the water treated in the jet unit
130
(the water containing a surface active agent of intermediate concentration). Therefore, the waste water discharged from the shower unit
140
contains a surface active agent of low concentration.
Then, the substrate
2
is fed to an ultrasonic cleaning unit
150
by means of transfer rollers
111
. A pure water, to which an ultrasonic vibrational energy is applied, is jetted out of an ultrasonic nozzle
154
driven by an oscillator
153
to be sprayed on the substrate
2
. Thus, the relatively fine particles adhered to the substrate
2
are removed, and the water used in the shower unit
140
is washed out. Thereafter, the substrate
2
is fed to a shower unit
160
by means of transfer rollers
111
, and a pure water is sprayed on the substrate
2
from shower nozzles
163
, so that the water used for the cleaning in the ultrasonic cleaning unit
150
is washed out. Furthermore, the waste waters discharged from the ultrasonic cleaning unit
150
and the shower unit
160
can be treated as usual waste waters since the concentrations of the surface active agents contained in the waste wafers are very low.
Then, the substrate
2
is fed to a draining unit
170
by means of transfer rollers
111
, and the water adhered to the surface of the substrate
2
is removed by air knives
172
. Thereafter, the substrate
2
thus drained is transported to a hot plate
180
to be dried thereon.
Then, an alignment layer material is applied on the substrate
2
thus dried, and the rubbing thereon is carried out to form an alignment layer thereon. Referring to
FIG. 9
, a step of cleaning the substrate
2
, on which the alignment layer has been formed, will be described. First, the substrate
2
is mounted in a bath
224
of an ultrasonic cleaning unit
220
by means of a loader (not shown). To this bath
224
, a cleaning solution is supplied from a mixing tank
210
via a pump
215
. This cleaning solution is prepared in the mixing tank
210
so as to contain a predetermined concentration of surface active agent. To the lower portion of the bath
224
, an ultrasonic vibrational energy is applied by means of an oscillator
223
. Therefore, the ultrasonic vibrational energy is applied to the substrate
2
in the cleaning solution to clean the substrate
2
.
Then, the substrate
2
is fed to a pure water jet unit
230
by means of transfer rollers
211
. Then, a high-pressure pure water is sprayed on the substrate
2
from jet nozzles
235
to replace the surface active agent with a pure water and to remove the particles on the substrate
2
. The pure water is pumped out of a pure water storage tank (not shown) to be supplied to the jet nozzles
235
. Furthermore, although the waste water discharged from the ultrasonic cleaning unit
220
contains a surface active agent of high concentration, and the waste water discharged from the pure water jet unit
230
contains a surface active agent of intermediate concentration.
Then, the substrate
2
is fed to a shower unit
240
by means of transfer rollers
211
, and a pure water is sprayed on the substrate
2
from shower nozzles
243
. Thus, the surface active agent and the water used in the jet unit
230
are washed out. The waste water discharged from the shower unit
240
contains a surface active agent of low concentration.
Then, the substrate
2
is fed to an ultrasonic cleaning unit
250
by means of transfer rollers
211
. Then, a pure water, to which an ultrasonic vibrational energy has been applied, is jetted out of an ultrasonic nozzle
254
driven by an oscillator
253
to be sprayed on the substrate
2
. Thus, the relatively fine particles adhered to the substrate
2
are removed, and the water used in the shower unit
240
is washed out.
Thereafter, the substrate
2
is fed to a shower unit
260
by means of transfer rollers
211
. Then, a
Furuya Hiroaki
Hayamizu Naoya
Nagahara Yoshiyuki
Nonaka Toshitaka
Okoshi Noriko
Kabushiki Kaisha Toshiba
Talbot B K
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