Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2001-09-13
2004-08-10
Eckert, George (Department: 2815)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S149000, C349S152000, C349S153000
Reexamination Certificate
active
06774968
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a liquid crystal device which forms text images and so on by using liquid crystal to modulate light and to an electronic apparatus which is formed using the liquid crystal device.
BACKGROUND ART
Recently, liquid crystal devices have been widely used in display units of electronic apparatuses such as portable computers, mobile telephones, video cameras, and so on. In general, these liquid crystal devices are formed such that a pair of substrates, each having electrodes formed thereon are bonded by a ring of sealing material such that the electrodes are oriented parallel to each other, and the liquid crystal is encapsulated in the region enclosed by the pair of substrates and the sealing material. In these liquid crystal devices, images such as text, numerals, graphics, and so on are displayed by controlling the orientation of the liquid crystal encapsulated between the pair of substrates at each pixel.
Among these liquid crystal devices, there are simple matrix liquid crystal devices which do not use active elements and active matrix liquid crystal devices which use active elements. TFD (Thin Film Diode) elements, which are two-terminal active devices, and TFT (Thin Film Transistor) elements, which are three-terminal active devices, are known as such active elements.
Conventionally, as shown in
FIG. 15
, for example, simple matrix liquid crystal devices which are formed such that a pair of substrates
151
a
and
151
b
made of glass or the like are bonded by a ring of sealing material
152
made of an epoxy resin or the like are known. The first one of the substrates, substrate
151
a
, has a substrate projecting part
153
a
which projects further outside than the other substrate
151
b
, and the other substrate
151
b
has a substrate projecting part
153
b
which projects further outside than the first substrate
151
a.
A plurality of strip-shaped electrodes
154
a
are formed of, for example, ITO (Indium Tin Oxide) on the inside surface of the first substrate
151
a
, and a plurality of strip-shaped electrodes
154
b
are formed of, for example, ITO on the inside surface of the other substrate
151
b
. When the pair of substrates
151
a
and
151
b
are bonded, these electrodes
154
a
and
154
b
orthogonally intersect each other, and each intersection point forms one pixel.
The electrodes
154
a
formed on the first substrate
151
a
have wiring lines
156
a
which extend onto the substrate projecting part
153
a
by passing through the sealing material
152
, and, at the same time, also have dummy patterns
157
a
which pass through the sealing material
152
at the side opposite to the substrate projecting part
153
a
. Electrodes
154
b
are also formed on the other substrate
151
b
in the same way. Liquid crystal driving ICs (Integrated Circuits; not shown in the drawing) are mounted on the substrate projecting parts
153
a
and
153
b
, and the wiring lines
156
a
of the electrodes
154
a
and the wiring lines
156
b
of the electrodes
154
b
are connected to the terminals of these liquid crystal driving ICs.
Liquid crystal is encapsulated in the region enclosed by the substrate
151
a
, the substrate
151
b
, and the sealing material
152
. This region is called a liquid crystal encapsulating region R. By controlling the voltage applied to this liquid crystal at each pixel, defined by the intersection points of the electrodes
154
a
and the electrodes
154
b
, light which is incident from outside the substrate
151
a
or the substrate
151
b
and transmitted therethrough is modulated at each pixel, and, accordingly, an image such as text is displayed on the outer side of the substrate
151
a
or the substrate
151
b.
In the conventional liquid crystal device, if a structure in which the wiring lines
156
a
pass underneath the sealing material
152
at the substrate projecting part
153
a
side while, on the other hand, the electrodes
154
a
do not pass underneath the sealing material
152
at the side opposite the substrate projecting part
153
a
is used, since the cell thickness at the end of the liquid crystal panel at the side opposite the substrate projecting part
153
a
becomes smaller by an amount equal to the part having no electrodes
154
a
, the cell thickness between the substrate projecting part
153
a
side and the side opposite thereto becomes nonuniform. When such a nonuniformity in the cell thickness occurs, the threshold voltage Vth at which the liquid crystal is turned ON/OFF becomes nonuniform between the substrate projecting part
153
a
side and the side opposite thereto, and, for that reason, a problem occurs in that the display quality of the liquid crystal device is reduced.
In the conventional liquid crystal device, the reason why the dummy patterns
157
a
, which pass underneath the sealing material
152
at part of the electrodes
154
positioned at the side opposite to the substrate projecting part
153
a
, are formed is that they prevent the height of the liquid crystal encapsulating region R, that is to say, the cell gap height, or in other words, the cell thickness, between the substrate projecting part
153
a
side and the side opposite thereto from becoming nonuniform.
However, in the conventional liquid crystal device in which the dummy patterns
157
a
are provided as described above, the configuration is such that the dummy patterns
157
a
are formed by extending the electrodes
154
a
while maintaining their width, and that is why the width of the dummy patterns
157
a
is the same as the width of the electrodes
154
a
. Accordingly, the ratio of the area underneath the sealing material
152
occupied by the wiring lines
156
a
, which pass through the sealing material
152
at the substrate projecting part
153
a
side, is different from the ratio of the area underneath the sealing material
152
occupied by the dummy patterns
157
a
, which pass through the sealing material
152
at the side opposite the substrate projecting part
153
a
. In particular, the ratio of the area occupied by the dummy patterns
157
a
at the side opposite the substrate projecting part
153
a
is larger.
Generally, in order to maintain the cell thickness at the sealing material, spherical or cylindrical spacers
158
are dispersed therein. However, when the ratio of the area occupied by the wiring lines
156
a
and the ratio of the area occupied by the dummy patterns
157
a
differ from each other, the number of spacers
158
sitting on top of the wiring lines
156
a
is not the same as the number of spacers
158
sitting on top of the dummy patterns
157
a
. In particular, the number at the substrate projecting part
153
a
side, where the area occupation ratio is small, is smaller than the number at the dummy pattern
157
a
side, where the area occupation ratio is large.
There is a tendency for the spacers
158
in the sealing material
152
to be compressed and crushed by the pair of substrates
151
a
and
151
b
; however, compared to the large number of spacers sitting on the dummy pattern
157
a
, where the area occupation ratio is large, the small number of spacers
158
sitting on the wiring lines
156
a
, where the area occupation ratio is small, are crushed to a greater extent. Accordingly, when the extent to which the spacers
158
are crushed at the two sides of the liquid crystal panel is different, a nonuniformity in the cell thickness occurs between one side of the liquid crystal panel and the other side, even when the dummy patterns
157
a
are formed. As a result, there is a problem in that the display quality deteriorates due to nonuniformity in the threshold voltage Vth.
Among liquid crystal devices, those having a structure in which liquid crystal driving ICs are directly mounted on the substrate projecting parts by the so-called COG (Chip On Glass) method are known. In these COG-method liquid crystal devices, since the plurality of electrodes which form the liquid crystal display region must be made to converge towards the terminals of the liquid crystal driving ICs o
Eckert George
Harness & Dickey & Pierce P.L.C.
Lee Eugene
LandOfFree
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