Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2002-04-11
2004-09-21
Kim, Robert H. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S154000, C349S155000, C349S157000
Reexamination Certificate
active
06795153
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a display panel as represented by a liquid crystal cell, more specifically to a technology suitable for obtaining a narrow-frame liquid crystal display panel.
Liquid crystal display devices are remarkably widespread as image display devices for personal computers and various other monitors. Typical liquid crystal display devices of this kind include a backlight, which is a planar light source for illumination, that is provided on a back side of the liquid crystal cell such that the backlight irradiates a liquid crystal layer having predetermined expansion to even brightness as a whole, whereby images formed on the liquid crystal layer are visualized.
The liquid crystal cell is comprised of two glass substrates being laminated together via the liquid crystal layer. Surrounding portions of the two glass substrates are sealed with a sealing material, and a liquid crystal material is filled into a space between the two glass substrates and surrounded by the sealing material, whereby a liquid crystal layer is formed. While a part of the liquid crystal cell surrounded by the sealing material constitutes a display area, the part provided with the sealing material does not constitute the display area, but instead is referred to as a frame. Because it is desirable to obtain a wide display area for the resulting structure, the width of the frame should be made as narrow as possible, but still able to function as required.
FIGS.
16
(
a
) to
16
(
c
) are views showing a conventional liquid cell, wherein FIG.
16
(
a
) is a plan view thereof; FIG.
16
(
b
) is a cross-sectional view taken along line A—A in FIG.
16
(
a
); and FIG.
16
(
c
) is an enlarged, partial view of a corner portion of the liquid crystal cell in FIGS.
16
(
a
) and
16
(
b
).
In FIGS.
16
(
a
) to
16
(
c
), a first substrate
110
is shown and consists of a flat hard glass. The major part of the top surface of first substrate
110
is occupied by a display area
113
having a colored layer composed of color filters (CF) of red, green and blue (RGB) formed therein. A sealing material
130
is applied thereto along the perimeter of display area
113
of first substrate
110
. Small spacers
40
are positioned over display area
113
in order to maintain a uniform thickness of the liquid crystal cell over the whole surface. A second substrate
120
is also shown, and also consists of a hard glass. It is provided with thin-film transistors (TFTs) on its surface opposite to first substrate
110
. When second substrate
120
is stacked on first substrate
110
, the applied sealing material
130
is pressed to adhere the two substrates
110
and
120
together. When these two substrates are adhered together, both are then subjected to a baking step (a thermal treatment), such that sealing material (e.g. epoxy resin)
130
is cured, whereby first substrate
110
and second substrate
120
are finally sealed together to form the liquid crystal cell. A liquid crystal material is filled into the liquid crystal cell thus formed, through an insertion port formed within sealing material
130
, whereby an end product now results. The sealing material is then finally sealed.
In FIG.
16
(
c
), sealing material
130
is applied as illustrated by solid lines
138
. However, when the sealing material is pressed by laminating the first and second substrates, it spreads as illustrated by dotted lines
139
. Here, when sealing material
130
spreads toward the inside of first substrate
110
, it may penetrate display area
113
partially. If it does penetrate as such, it may cause display defects on the corners of display area
113
. To avoid such penetration, it is necessary to distance the corners of display area
113
from an inner edge of sealing material
130
. As such, the space between the display area
113
and the inner edge of sealing material
130
must be relatively broad. Therefore, the outermost edges of display area
113
are limited and not readily expandable if a larger area is desired.
Various modes of attempts to achieve frame narrowing by controlling the behavior of the applied sealing materials are defined in Japanese Patent Laid-Open Publication No. 2000-193989 (and its USA counterpart U.S. Pat. No. 6,317,186 B1), both assigned to the same assignee as the present invention. These modes inhibit sealing material spread at corner portions of the liquid crystal cell. According to conventional methods (prior to those taught in Japanese Patent Laid-Open Publication No. 2000-193989 and U.S. Pat. No. 6,317,186 B1), a sealing material applied at a corner portion of a liquid crystal cell tended to spread inward, i.e. toward the display area, during laminating of the two glass substrates, and thus the display area was reduced. The various modes defined in Japanese Patent Laid-Open Publication No. 2000-193989 and U.S. Pat. No. 6,317,186 B1, are intended to prevent such spread.
One such mode is illustrated in FIG.
17
. Here, protruding (upstanding or upraised) portions
140
are provided on a glass substrate cell except at the corner portions thereof. These are along the top and side (as well as the bottom and opposing side, not shown) edges, as seen. As a result, a step is formed in the vicinity of the perimeter of the second substrate (
120
in FIG.
16
(
a
)) in a manner that upper surfaces of the corner portions are lower than the upper surfaces of protruding portions
140
. Sealing material
130
applied in the vicinity of the perimeters of the second substrate show less height at the corner portion, which is lower by the height of protruding portion
140
. Sealing material
130
at the corner portion is pressed less than the sealing material at protruding portion
140
during substrate lamination, by the amount equivalent to the height of the protruding portion. On the other hand, sealing material
130
applied over portions
140
is more pressed by the amount equivalent to the volume of the respective protruding portion. In other words, this mode modifies the inside edge of sealing material
130
at the corner portion from an arc (FIG.
16
(
c
)) to an approximate right angle by using this difference of pressed sealing material at the corner portion versus that in other regions (sides).
Another mode defined in Japanese Patent Laid-Open Publication No. 2000-193989 and U.S. Pat. No. 6,317,186 B1 is illustrated in FIG.
18
. This is an example of providing a protruding (upstanding or upraised) portion
150
having rectangular planes at the corner portions of second substrate
120
, so that a pressed amount of sealing material
130
is directed outwardly (from the display area
113
) toward the substrate's corners. Portion
150
is formed at the corner portion to coincide with a diagonal through the center of the liquid crystal cell. Sealing material
130
on an upper surface of the protruding portion is more pressed by second substrate
120
. Since sealing material
130
is applied thereto in a shape as illustrated in
FIG. 18
, the inside edge of the sealing material at the corner forms an approximate right angle, due to the increase in pressure on the sealing material
130
at protruding portion
150
.
When a sealing material is applied with a dispenser, the traveling speed of the dispenser along the outer regions of the substrates needs to be slowed down at the corner portions. Assuming that an amount of sealant discharge per unit of time is maintained constant, the amount of sealing material applied in the corner portion is increased. As a consequence, although the mode shown in
FIG. 17
provides certain advantages, further improvement is required in order to sufficiently inhibit sealing material
130
at the corner portion from spreading inward. In the mode shown in
FIG. 18
, the dispenser must move along a special trajectory at the corner portions during application of sealing material. That is, the trajectory of the dispenser becomes longer and more complex than the example shown in FIG.
17
. This added complexity is, obviously, not desirable fro
Hoffman, Warnick & D'Alessandro LLC
International Business Machines - Corporation
Kim Robert H.
Steinberg William H.
Wang George Y.
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