Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Reexamination Certificate
2000-11-13
2003-02-25
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
C349S058000, C349S141000, C349S149000
Reexamination Certificate
active
06525786
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a transverse electric liquid crystal display device, and more particularly to a transverse electric liquid crystal display device free from unevenness of display due to static electricity.
2. Description of the Related Art
In general, a liquid crystal panel is designed to have a liquid crystal material sealed in the gap between two glass substrates. A liquid crystal panel is composed of a rear-side glass substrate that has a thin-film transistor (TFT) formed on its liquid-crystal-side surface (hereafter referred to as the TFT-side glass substrate) and a glass substrate that has a color filter disposed between its surface and the liquid crystal material (hereafter referred to as the color-filter-side glass substrate).
FIG. 1
is a top view and side views illustrating the structure of a conventional liquid crystal panel. As shown in
FIG. 1
, a conventional liquid crystal panel is composed of two glass substrates of different sizes bonded together. On the liquid-crystal-side surface of a rear-side glass substrate
30
, a TFT for controlling turning ON/OFF of a liquid crystal picture element
33
is formed. By composing the liquid crystal panel of two glass substrates of different sizes, it is possible to prevent an input terminal
32
for feeding a signal to a picture element
33
from being covered by a display-surface-side glass substrate
31
. Accordingly, the rear-side glass substrate
30
is made larger in size than the display-surface-side glass substrate
31
in which a color filter is disposed. In this way, the two glass substrates are bonded together so that they have a projection
34
a
and a projection
34
b,
the projections
34
a
and
34
b
being so formed as to protrude horizontally and vertically, respectively, from the TFT-side glass substrate
30
over the color-filter-side glass substrate
31
. In order to feed a signal from outside to the liquid crystal panel, generally, as shown in
FIG. 1
, the glass substrate
30
needs to be so constructed that its two, longitudinal and lateral side edges, along which the input terminals
32
are formed, are left uncovered by the display-surface-side glass substrate
31
. Even though the liquid crystal panel is specially designed, at least one side edge of the glass substrate
30
needs to be left uncovered. In the liquid crystal panel as indicated as an area
35
, the two glass substrates are superimposed together at their side edges excluding those having the projections
34
a
or
34
b.
In the liquid crystal display device, the two substrates are each provided with an electrode in order to generate an electric field therebetween. This makes it possible to control orientation of liquid crystal molecules in the liquid crystal material sealed in the gap between the two glass substrates. As a result, a display image is formed. When the direction of the electric field is assumed to be the lengthwise direction, the transverse electric liquid crystal panel has electrodes arranged in a row only along the surface of the TFT-side glass substrate. In this construction, orientation of the liquid crystal molecules is controlled by applying to the liquid crystal molecules an electric field in the transverse direction. Accordingly, in a case where static electricity is applied to the surface of the TFT-side glass substrate or the color-filter-side glass substrate and then the electrostatic charge remains on the glass surface of the substrate, an electric field is generated in the lengthwise direction. This causes the liquid crystal molecules to be oriented in a fixed direction. As a result, it is not possible to control orientation of the liquid crystal molecules properly, and this leads to unevenness of display. As will be understood from the foregoing, a transverse electric liquid crystal panel tends to suffer from degradation of display quality due to static electricity, and therefore it necessitates a means for eliminating the undesirable effects of static electricity.
Conventionally, a construction is known in which, to absorb static electricity, a transparent conductive film is formed on the surface of the display-surface-side liquid crystal panel, and this transparent conductive film is connected to the casing with a conductive spacer or the like. For example, Japanese Patent Laid-open Publication No. Hei 9-258203 proposes a liquid crystal panel of this type (a conventional example 1).
FIG. 2
is a sectional view illustrating the structure of the transverse electric liquid crystal display device of the conventional example 1. As shown in
FIG. 2
, the transverse electric liquid crystal display device of the conventional example 1 is provided with a liquid crystal panel
101
and a circuit board
107
. The liquid crystal panel
101
is located above a backlight illumination device
113
and is sandwiched between polarizing plates
105
a
and
105
b.
The circuit board
107
is arranged adjacent to the liquid crystal panel
101
. The liquid crystal panel
101
is composed of a TFT-side glass substrate
102
and a color-filter-side glass substrate
103
. The TFT-side glass substrate
102
is disposed on the backlight-illumination-device
113
side of the display device and has an area larger than the color-filter-side glass substrate
103
. These two glass substrates are superimposed on each other so as to have a projection. The color-filter-side glass substrate
103
has a transparent conductive film
104
formed between its surface and the polarizing plate
105
b
that is located thereabove.
The projection provided in the liquid crystal panel
101
is built as a pressure-contacting portion
110
that acts as the connection between the TFT and a TCP (tape carrier package)
106
for driving the TFT. The TCP
106
has its one end connected to the pressure-contacting portion
110
and the other end connected to the circuit board
107
. The polarizing plate
105
a
and the polarizing plate
105
b,
which are formed on the bottom surface of the TFT-side glass substrate
102
and the top surface of the color-filter-side glass substrate
103
, respectively, are used to polarize the light coming from the backlight illumination device
113
that illuminates the liquid crystal panel
101
from the rear. Moreover, the display-surface-side polarizing plate
105
b
has an area smaller than the color-filter-side glass substrate
103
. This allows the transparent conductive film
104
, which is provided underneath the polarizing plate
105
b,
to be exposed so as to be connected to a casing
109
via a conductive spacer
112
. In this way, even if the display surface is brought into contact, for example, with a user, and then the static electricity therefrom is applied to the transverse electric liquid crystal panel
101
, it is possible to discharge the remaining static electricity into the casing
109
.
Moreover, Japanese Laid-open Publication No. Hei 11-185991 proposes a technique to protect electronic equipment against static electricity by making use of a ground of a circuit board mounted in a liquid crystal display device (a conventional example 2). According to the conventional example 2, electronic equipment provided with a panel, for example, a liquid crystal display panel, has a transparent conductive member formed on its panel surface. In this example, by connecting this transparent conductive member to the ground of the circuit board incorporated in the electronic equipment by the use of an electric conduction means, it is possible to discharge the static electricity applied to the panel surface through the transparent conductive member via the electric conduction means into the ground of the circuit board.
FIG. 3
is a sectional view illustrating the structure of the liquid crystal display device of the conventional example 2.
As shown in
FIG. 3
, inside a lower case
201
and an upper case
202
are arranged a main-circuit board
203
, a sub-circuit board
204
, and a liquid crystal panel
205
. The sub-circuit board
204
and the liquid
Duong Thoi V
Scully Scott Murphy & Presser
Sikes William L.
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