Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2002-03-19
2004-04-20
Chowdhury, Tarifur R. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S151000
Reexamination Certificate
active
06724456
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a liquid crystal display device characterized in a structure of connection between electrode driving ICs mounted on substrates and electrodes such as scanning electrodes, signal electrodes, and the like which are provided on the substrates.
2. Description of the Related Art
Super twisted nematic (STN) liquid crystal display devices are employed most widely for small display units such as cellular phones and the like. Since a decrease in size of an outer case and an increase in size of an image display portion are simultaneously demanded in a cellular phone in particular, it is necessary to devise the structure of the liquid crystal display device and the arrangement of electrode driving ICs. Recently, the number of pixels increases to perform display in colors and gradations as well, and thus a small liquid crystal panel for a cellular phone is offered, in which a scanning electrode driving IC and a signal electrode driving IC are arranged on two sides respectively similarly to the arrangement of the electrode driving ICs in a large liquid crystal panel. Such a structure, however, is not desired in terms of design because of broken symmetry of the liquid crystal panel.
Therefore, a configuration using a one-chip electrode driving IC in which a scanning electrode driving circuit, a signal electrode driving circuit, an image memory, and a display control circuit are formed in one electrode driving IC, or a configuration in which all the driving circuits are mounted on one side of one substrate, is begun to be used.
An arrangement of members and a wiring state in a conventional liquid crystal display device using a one-chip electrode driving IC are explained here using
FIG. 18
to FIG.
21
.
FIG. 18
is a plan view of the liquid crystal display device,
FIG. 19
is a side view of the same as viewed from a direction of an arrow A in
FIG. 18
,
FIG. 20
is a plan view showing an arrangement of electrodes in the liquid crystal display device, and
FIG. 21
is a view for explaining an arrangement of connecting wirings connected to scanning electrodes in the liquid crystal display device. In these drawings, the illustration of optical members such as a polarizer, a reflector and the like is omitted.
In this liquid crystal display device, an electrode driving IC
62
is mounted on an upper substrate
61
which is made of glass. A method, in which the electrode driving IC is mounted on the substrate as described above, is often employed. (It is called chip-on-board. With a glass substrate, it is called chip-on-glass and hereinafter referred to as COG.) As shown in FIG.
18
and
FIG. 19
, the electrode driving IC
62
, a lower substrate
63
which is made of glass, and a connecting film circuit (called a flexible printed circuit, and hereinafter referred to as an FPC)
64
are adhered to a back face of the upper substrate
61
. Among them, the upper substrate
61
and the lower substrate
63
are adhered to each other with a sealing portion
69
and hold a liquid crystal layer sandwiched therebetween.
On these substrates, electrodes are formed on respective faces on the liquid crystal layer sides. In
FIG. 20
, solid lines show the electrodes formed on (the back face of) the upper substrate
61
, and phantom lines show the electrodes formed on the lower substrate
63
. Broken lines represent repetition of respective components.
As shown in
FIG. 20
, scanning electrodes
65
are formed of ITO (indium tin oxide) on the lower substrate
63
. Further, signal electrodes
66
, wirings
68
for connecting them to the FPC
64
, and connecting wirings
67
for connecting the scanning electrodes
65
and electrode driving terminals of the electrode driving IC
62
are formed of ITO on the back face of the upper substrate
61
. Then portions where the scanning electrodes
65
and the signal electrodes
66
overlap (oppose) each other in a plan view become individual pixels, and a region where these pixels perform effective display based on image data becomes an image display portion
612
shown by the phantom line.
A face with terminals of the electrode driving IC
62
and the connecting wirings on the upper substrate
61
are electrically connected to each other with an anisotropic conductive film (hereinafter, referred to as an ACF) sandwiched therebetween. Similarly, not shown wirings on the FPC
64
and the wirings
68
on the upper substrate
61
are also connected to each other by an ACF within connecting regions
611
.
FIG. 21
shows only members associated with the connection between the scanning electrodes
65
and the electrode driving IC
62
. As shown in this drawing, the scanning electrodes
65
and the connecting wirings
67
are connected to each other through the sealing portion
69
at connecting regions
610
. The sealing portion
69
, in which conductive particles are mixed here, is an anisotropic conductive sealing portion which makes conduction only in a direction perpendicular to the substrates
61
and
63
.
Assuming that the place where the electrode driving IC
62
is mounted is the upper side of the image display portion
612
, the scanning electrode driving terminals on the left-hand side of the electrode driving IC
62
are connected to the scanning electrodes
65
arranged at the upper half of the image display portion
612
, and the scanning electrode driving terminals on the right-hand side are connected to the scanning electrodes
65
arranged at the lower half of the image display portion
612
.
Further, the connecting wirings
67
for the scanning electrode driving terminals extending from the lower side of the electrode driving IC
62
in
FIG. 21
are connected to the scanning electrodes
65
in the connecting regions
610
which are arranged at the upper side of the sealing portion
69
. The connecting wirings
67
extending from the upper side thereof are connected to the scanning electrodes
65
in the connecting regions
610
which are arranged at the left-hand side (or the right-hand side) of the sealing portion
69
.
In the case of a small number of display digits provided as in an early-type liquid crystal display panel for a cellular phone, the connecting wirings
67
provided only at the upper side of the image display portion
612
enabled connection between the electrode driving IC
62
and the scanning electrodes
65
. In the case of a large number of display digits, however, sufficient region for connection can not be obtained if wirings are drawn only from the upper side of the image display portion, because the pitch of the connecting regions
610
needs to be made larger than the pitch of the connecting wirings
67
. Accordingly, as shown in FIG.
19
and
FIG. 20
, the connecting wirings
67
need to be routed from the left- and right-hand sides of the image display portion
612
.
In the liquid crystal display device for a cellular phone, the demand is always to decrease the size of a glass external shape as described above. On the other hand, an increase in display information volume and an increase in the number of scanning electrodes of the liquid crystal display device require widening a region for the connecting wirings, resulting in increased glass external shape. Further, a pair of substrates are bonded together with a sealing material, in which a problem is caused from situation wherein a disregard for the positional relationship between a sealing portion where the sealing material is provided and the region for the connecting wirings might cause a decrease in productivity and display quality.
In other words, when fabricating a liquid crystal display device, a method is used which bonds a pair of large substrates together and cuts out a plurality of liquid crystal display devices therefrom, in which if the connecting wirings are provided outside the sealing portion, the cutting for cutting out the liquid crystal display devices is performed near the connecting wirings. This possibly exerts adverse effects on the connecting wirings such as break lines due
Chowdhury Tarifur R.
Chung David
Citizen Watch Co. Ltd.
Westerman Hattori Daniels & Adrian LLP
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