Telephonic communications – Polystation line system – Connected to central office
Reexamination Certificate
2001-10-11
2004-01-20
Dudek, James (Department: 2871)
Telephonic communications
Polystation line system
Connected to central office
Reexamination Certificate
active
06681005
ABSTRACT:
This application incorporates by reference Taiwanese application Serial No. 90114213, Filed Jun. 12, 2001.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a device for manufacturing a liquid crystal display (LCD) panel and a fabrication method therefor, particularly to a method capable of forming a uniform cell gap.
2. Description of the Related Art
Compared to a conventional display panel, the liquid crystal display (LCD) panel has the potential of lightweight, low power consumption and high resolution for which are generally beloved by the consuming public. Also, the other portable products, such as personal digital assistant (PDA) and cellular phone, enjoy a rapid growth in the market. With the increasing demand, the image display of those portable products is expected to have the same resolution as that of a personal computer. For example, the liquid crystal on silicon (LCOS) panel, which generally applies to a small display panel, is a panel composed of a silicon substrate and a glass substrate with liquid crystal injected between. As such LCOS panel differs from the common liquid crystal panel that utilizes two substrates both made of glass, it can be smaller and lighter and can provide a high-resolution display quality. The resolution of a LCOS panel is shown by the number of pixels, similar to a liquid crystal panel; that is, the more pixels it possesses the higher resolution it displays. Furthermore, the semiconductor process, like the CMOS technology, finds application in the production of the driving circuit of pixels in a LCOS panel. By this method, the silicon wafer as the substrate can be manufactured in employing the 0.35 um semiconductor process. Thus, there is no need to throw in extra investment in production equipment, and the display resolution of a LCOS panel is greater than that of a glass-substrate liquid crystal panel.
Generally, the LCOS panel has two basic types: transmissive and reflective. Nevertheless, the most research and development work is centered on the reflective LCOS panel. Referring to
FIG. 1
, it is a sectional view of a pixel of a reflective LCOS panel. The LCOS panel comprises a first plate
100
and a second plate
101
, wherein said second plate
101
made of a silicon substrate
102
consists of a thin film transistor (TFT)
106
for controlling pixel movement, a light shielding film
107
for blocking light irradiation on the TFT, a capacitor
108
for sustaining pixel brightness, a metal layer
111
in connecting the TFT
106
with the capacitor
108
, an insulating layer
109
capping the metal layer
111
, a pixel electrode
110
, and a reflector
112
, and wherein the second plate
100
made of a glass substrate
120
includes a transparent electrode (ITO)
118
. The first substrate
100
and the second substrate
101
are assembled and inserted with a liquid crystal molecule
115
to form a liquid crystal layer
114
in between the two substrates. In addition, an orientation film
113
and
116
are formed above the reflector
112
and beneath the ITO
118
, respectively.
With reference to
FIG. 1
, the incoming light passing through the liquid crystal layer
114
(as shown in Arrow I) directly emerges from the glass substrate
120
via the reflector
112
(as shown in Arrow O). With the variance of voltage charged on the pixel electrode
110
, the liquid crystal molecule
115
changes its alignment, so as to control the polarization of light passing through the liquid crystal layer
114
. Therefore, the emerging light will, through the application of the polarizer (not shown in
FIG. 1
) disposed above the substrate
120
, be visible.
Referring to
FIG. 2
which is a schematic diagram of
FIG. 1
, the LCOS panel consists of the glass substrate
120
and the silicon substrate
102
, both of which possess a plurality of corresponding pixel electrodes, such as pixel electrodes
204
a
and
204
b
, and the cell gap H, the distance between the corresponding pixel electrodes, is inserted with the liquid crystal (other elements are omitted in FIG.
2
). The optical effect of the liquid crystal will vary with the width of the cell gap. An uneven cell gap between the substrates resulting in the interfering ring visible to the naked eyes is called “Newton ring” that may cause injury to the display effect of the LCOS pixel.
Moreover, unlike the large size LCD panel, the LCOS application is aimed at the small size panel, such as the projector or the LC panel used in projection TV. The LCOS panel with general pixel size of 0.7 inch, 0.9 inch or 1.3 inch needs to amplify its image to 60 to 100 inch if applied to projection TV. Under such a high amplification rate, the imperfection shown in the applied product will become even more conspicuous once the display effect of the panel itself is not so satisfactory. Therefore, an important goal for research efforts is retaining a uniform cell gap H that is to control the space between the glass substrate
120
and the silicon substrate
102
.
Typically, the solution to the problem of an uneven cell gap is to apply spacers randomly between the liquid crystal layers.
FIG. 3
depicts the sectional view of a traditional LCOS panel. The LCOS panel consists of a glass substrate
320
and a silicon substrate
302
with a liquid crystal layer
306
inserted in between. A plurality of corresponding pixel electrodes, like electrodes
304
a
and
304
b
, is arranged between the substrates, wherein the cell gap H between electrodes
304
a
and
304
b
is upheld by virtue of disposing spacers
308
. When the glass substrate
320
and the silicon substrate
302
are uneven or suffer external pressure, the spacers can prevent a direct contact of the two substrates. Meanwhile, this method incurs many shortcomings that, in addition to the need for strictly controlling the particle size of each spacer, these randomly disposed spacers are inclined to gather in particular place during liquid crystal injection, thereby failing to produce a uniform cell gap H. Moreover, in its application in projection TV, the disposed spacers that incidentally fall above the pixel will result in tiny black spots in the display. Thus, the shadow caused by applying spacers randomly will decrease the display performance of the LCOS panel.
Another conventional method of controlling the cell gap is to form slender protrusions between the pixels.
FIG. 4
shows the sectional view of another conventional LCOS panel, wherein all pixels
402
are spaced apart from each other by a spacing
404
. The pixel
402
corresponds to the display area of the LCOS panel, whereas the spacing
404
corresponds to the non-display area. The protrusion is made of curable material after UV and heating treatments, e.g. silicon dioxide or silicon nitride, and is formed in the spacing
404
with a shape having a width approximately 0.35-0.5 micron and a height approximately 3-5 micron. The protrusion is also called a photo spacer
406
, which is perpendicular to the pixel
402
. The photo spacer
406
formed in the spacing
404
is able to uphold the space between the glass substrate and the silicon substrate so as to uniformize the cell gap. Even so, such method has several disadvantages; for example, the slim structure of said photo spacer
406
causes process difficulty and said photo spacer is vulnerable for its lack of sustentation. Furthermore, the bottom part of said photo spacer is likely to have deformation when affected by the heat in the process. If the bottom deformation is too severe, it may cover up the pixel
402
partially, as shown in the dotted line
406
of
FIG. 4
, thereby hampering the aperture ratio of the pixel
402
; on the other hand, the liquid crystal is susceptible to contamination during the process.
For the above, a solution is desirous as to how to maintain a uniform cell gap width H in order to prevent a Newton ring and display an excellent picture quality.
SUMMARY OF THE INVENTION
The present invention is intended to provide a device for manufacturing a liquid crystal display panel with uniform
Liao Bing-Jei
Liu Chung-Yuan
Chi Mei Optoelectronics Corp.
Dudek James
Rabin & Berdo P.C.
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