Image display device

Computer graphics processing and selective visual display system – Plural display systems – Tiling or modular adjacent displays

Reexamination Certificate

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Reexamination Certificate

active

06177912

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to an image display device for use in AV (Audio and Visual) devices and OA (Office Automation) devices.
BACKGROUND OF THE INVENTION
Conventionally, various image display devices such as a home television set have been adopted in AV devices and OA devices. Such an image display device includes, for example, a CRT (Cathode Ray Tube), a liquid crystal display device, a plasma display device (Plasma Display Panel), an EL (electroliminescent) display device, an LED (Light Emitting Diode) display device, and other types of devices.
In recent years, there has been a demand for making these image display devices lighter, thinner, less power consuming, and finer, and making the display larger. To this date, many display devices meeting such a demand have been developed, and some of them have already been used in actual application.
Of various display devices as mentioned above, the liquid crystal display device has such advantages in that, compared with other display devices, the thickness (depth) is far thinner, the power consumption is low, and a full color can be realized with ease. For this reason, the liquid crystal display device has been used in a variety of fields in various ways, and is considered to be the best candidate for realizing a larger screen.
However, in order to realize a liquid crystal display device with a larger screen, the following problem must be overcome. That is, in the liquid crystal display device, when the screen is made larger, the fraction defective is abruptly increased due to breakage of a signal wire and a pixel failure in the manufacturing process. This inevitably raises the price of the liquid crystal display device.
In order to solve this problem and to realize a larger screen, a variety of liquid crystal display devices of the multi-panel system have been suggested. In the liquid crystal display devices of the multi-panel system, a plurality of liquid crystal panels are connected to one another so as to constitute a single liquid crystal display device.
However, in the liquid crystal display devices of the multi-panel system, the connected portion between liquid crystal panels, namely, a “seam” between liquid crystal panels becomes noticeable on the display. This is caused by the light from the backlight leaking through a gap at the connected portion between liquid crystal panels. Thus, in order to realize a liquid crystal display device capable of natural displaying on a large screen, a technique for disguising the seam is needed.
In order to realize such technique, the applicants of the present invention have suggested a liquid crystal display device adopting a new type of the multi-panel system in Japanese Unexamined Patent publication No. 122769/1996 (Tokukaihei 8-122769).
FIG. 11
is a cross sectional view which schematically shows, as such a liquid crystal display device, the arrangement of a liquid crystal display device
101
.
As shown in
FIG. 11
, the liquid crystal display device
101
is provided with a plurality of liquid crystal panels
102
of the active matrix type. In the following, for simplicity, explanations will be given through the case where the number of liquid crystal panel
102
of the liquid crystal display device is two.
A liquid crystal panel
102
has an arrangement wherein a TFT substrate
103
and a CF substrate
104
are combined with each other by a sealant
105
, and liquid crystal
106
is enclosed therebetween. The liquid crystal panels
102
are connected adjacent to each other by an adhesive
108
to a large reinforcing substrate
107
having substantially the same refractive index as that of glass from which the TFT substrate
103
and the CF substrate
104
are made.
On substantially the entire surface of the outer side of the reinforcing substrate
107
, a polarizing plate (polarizer)
109
is provided. Also, on substantially the entire surface of the outer side of the liquid crystal panels
102
, a polarizing plate (polarizer)
110
is provided. The polarization axes of the polarizing plates
109
and
110
are orthogonal to each other.
In the described arrangement, leakage of light from the gap between the liquid crystal panels
102
is prevented by the polarizing plates
109
and
110
which are in the Cross Nicole state. However, in the case of adopting, as the adhesive
108
which binds the edge surfaces of the liquid crystal panels
102
, adhesive resin, etc., having birefringence, there is a case where the transmitted light from the backlight, which is determined by the polarizing plates
109
and
110
, is modulated by the adhesive
108
. As a result, even when the polarizing plates
109
and
110
are in the Cross Nicole state, there is a case that the light from the backlight is transmitted through a connected portion
112
of the liquid crystal panels
102
, and partial leakage of light is caused.
As a countermeasure, as shown in
FIG. 11
,
FIG. 12
, and
FIG. 13
, on predetermined positions on the edge surfaces of the liquid crystal panels
102
which are connected adjacent to each other, light-shields
51
a
and
51
b
, each having a predetermined height (length in a direction perpendicular with respect to the edge surface) are provided, respectively. As shown in
FIG. 13
, when connecting the edge surfaces of the liquid crystal panels
102
, the light-shields
51
a
and
51
b
are connected to each other so as to form a light shielding film, filling the gap between the liquid crystal panels
102
. With this arrangement, light passing through the connected portion can be blocked by the light shielding film
51
, thus preventing leakage of light from the connected portion
112
.
Note that, the light-shields
51
a
and
51
b
are also known as a side-black, and are made of, for example, a black silicon rubber. The side-black may be provided, as above, on each edge surface of the liquid crystal panels
102
, or may be provided on only one of the edge surfaces. Also, the predetermined position where the side-black is to be provided is a position which does not prevent light from passing through display pixels adjacent to the connected portion
112
between the liquid crystal panels
102
, and in this case, a substantially central portion on each edge surface of the liquid crystal panels
102
in a direction of the panel thickness. Since detailed explanation of such predetermined position is discussed in the above-mentioned publication, a further explanation thereof is omitted here.
Despite the described advantage, the arrangement of the liquid crystal display device
101
presents the following problems.
For example, in the case of making a 40 inch (approximately 80 cm×60 cm) multi-panel liquid crystal display device
101
by connecting two 29 inch (approximately 40 cm×60 cm) liquid crystal panels
102
, the length in the lengthwise direction on the edge surfaces of the liquid crystal panels
102
at the connected portion
112
becomes substantially 60 cm, and a side-black having a height of substantially 30 &mgr;m is formed on each of the edge surfaces along the length of substantially 60 cm.
FIG. 14
is an explanatory drawing which shows how the glass substrate is cut by a dicing process using a diamond blade. As shown in
FIG. 14
, when a liquid crystal panel, made of the glass substrate, having a thickness of substantially 2 mm is cut along the cutting line of substantially 60 cm, the cutting edge surface takes the shape of X-Z plane in
FIG. 14
, with a profile irregularity of substantially 20 &mgr;m to 30 &mgr;m. Note that, here, the profile irregularity is the distance between the crest and the trough of the waviness on the cutting edge surface of the substrate in Y direction.
Possible reasons for the profile irregularity in the above range are {circle around (1)} reduced mechanical accuracy of a dicing device as a result of adopting a large dicing device in accordance with the work size (size of glass substrate to be cut) and {circle around (2)} wobbling blade rotating at a high speed as a result of increased processing s

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