U.S. patent application number 10/351388 was filed with the patent office on 2003-06-26 for display panel.
This patent application is currently assigned to Sharp Kabushiki Kaisha. Invention is credited to Nakajima, Kazuko, Nakajima, Mutsumi.
Application Number | 20030117537 10/351388 |
Document ID | / |
Family ID | 13533250 |
Filed Date | 2003-06-26 |
United States Patent
Application |
20030117537 |
Kind Code |
A1 |
Nakajima, Mutsumi ; et
al. |
June 26, 2003 |
Display panel
Abstract
A display panel of the present invention includes: a first
substrate and a second substrate opposing each other with a display
medium interposed therebetween; a plurality of signal lines and a
plurality of scanning lines provided on the first substrate to
cross each other and be insulated from each other; and a plurality
of pixel electrodes each provided in a vicinity of an intersection
between one of the plurality of signal lines and one of the
plurality of scanning lines so as to be connected to the one of the
plurality of signal lines and the one of the plurality of scanning
lines via a switching element, while the plurality of pixel
electrodes define a display region of the display panel. At least
one of each of the plurality of signal lines and each of the
plurality of scanning lines has a high resistance portion proximate
an end thereof outside the display region. The high resistance
portion is interposed at least partially between the first
substrate and the second substrate.
Inventors: |
Nakajima, Mutsumi;
(Nara-shi, JP) ; Nakajima, Kazuko; (Tenri-shi,
JP) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
1100 N GLEBE ROAD
8TH FLOOR
ARLINGTON
VA
22201-4714
US
|
Assignee: |
Sharp Kabushiki Kaisha
|
Family ID: |
13533250 |
Appl. No.: |
10/351388 |
Filed: |
January 27, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10351388 |
Jan 27, 2003 |
|
|
|
09047509 |
Mar 25, 1998 |
|
|
|
Current U.S.
Class: |
349/40 |
Current CPC
Class: |
G02F 1/136204
20130101 |
Class at
Publication: |
349/40 |
International
Class: |
G02F 001/1333 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 26, 1997 |
JP |
9-073963 |
Claims
What is claimed is:
1. A display panel, comprising: a first substrate and a second
substrate opposing each other with a display medium interposed
therebetween; a plurality of signal lines and a plurality of
scanning lines provided on the first substrate to cross each other
and be insulated from each other; and a plurality of pixel
electrodes each provided in a vicinity of an intersection between
one of the plurality of signal lines and one of the plurality of
scanning lines so as to be connected to the one of the plurality of
signal lines and the one of the plurality of scanning lines via a
switching element, while the plurality of pixel electrodes define a
display region of the display panel, wherein: at least one of each
of the plurality of signal lines and each of the plurality of
scanning lines has a high resistance portion proximate an end
thereof outside the display region; and the high resistance portion
is interposed at least partially between the first substrate and
the second substrate.
2. A display panel according to claim 1, wherein the high
resistance portion is formed of a material including semiconductor,
a metal, and a metal oxide.
3. A display panel according to claim 1, wherein the high
resistance portion is formed of a film having a specific resistance
higher than a specific resistance of a film which forms portions of
the plurality of signal lines and the plurality of the scanning
lines in the display region.
4. A display panel, comprising: a first substrate and a second
substrate opposing each other with a display medium interposed
therebetween; a plurality of signal lines and a plurality of
scanning lines provided on the first substrate to cross each other
and be insulated from each other; and a plurality of pixel
electrodes each provided in a vicinity of an intersection between
one of the plurality of signal lines and one of the plurality of
scanning lines so as to be connected to the one of the plurality of
signal lines and the one of the plurality of scanning lines via a
switching element, while the pixel electrodes define a display
region of the display panel, wherein: a first electrode, for
inducing an electrostatic charge applied to the display panel to
the first electrode, is provided outside the display region in a
vicinity of an end of at least one of each of the plurality of
signal lines and each of the plurality of scanning lines, the first
electrode being insulated from the plurality of signal lines and
the plurality of scanning lines.
5. A display panel according to claim 4, wherein the first
electrode is electrically connected to a counter electrode on the
second substrate.
6. A display panel according to claim 4, wherein the first
electrode is superimposed on, and insulated from, the plurality of
signal lines and the plurality of scanning lines.
7. A display panel according to claim 4, wherein the first
electrode is interposed between, and insulated from, two adjacent
ones of the plurality of signal lines and the plurality of scanning
lines.
8. A display panel according to claim 4, wherein the first
electrode is wider or larger in area than the portion of the
plurality of signal lines and the plurality of scanning lines near
an edge of the first substrate.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a display panel such as a
liquid crystal display panel used in television sets, personal
computers, word processors, OA (Office Automation) apparatuses, or
the like.
[0003] 2. Description of the Related Art
[0004] Such a liquid crystal display panel has a structure where a
pair of substrates are provided so as to oppose each other with a
liquid crystal layer being interposed therebetween as a display
medium. One of the pair of substrates is an active matrix
substrate, in which a plurality of signal lines and a plurality of
scanning lines are provided so as to cross each other via an
insulation film. A pixel electrode is provided in the vicinity of
an intersection between the signal line and the scanning line and
is connected to the signal lines and the scanning lines via a TFT
(Thin Film Transistor) as a switching element. Each of the pixel
electrodes is provided with a signal from the corresponding signal
line via the TFT, which is switched by a signal from the
corresponding scanning line. Thus, a voltage is applied to the
liquid crystal layer between the pixel electrode and an opposing
counter electrode, thereby changing the optical characteristics of
the corresponding portion of the liquid crystal layer between the
electrodes. This change in the optical characteristics is visually
perceived as a display pattern.
[0005] When a voltage of, for example, about 100 V or more
generated by an electrostatic charge, or the like, is applied to
the signal line or the scanning line, the characteristics of the
TFT may deteriorate, or the insulation film between the signal line
and the scanning line may be broken. In such a case, a linear
defect or a display non-uniformity may appear in a displayed image,
thus lowering the display quality. Since an electrostatic charge of
such a magnitude often occurs during a step of producing the active
matrix substrate or a step of rubbing an alignment film for
aligning the liquid crystal layer, it is impossible to completely
avoid such problems as described above.
[0006] In view of this, an active matrix substrate provided with a
short-circuiting line, as shown in FIGS. 7 and 8, has been
conventionally used.
[0007] FIG. 7 shows an equivalent circuit of such a conventional
active matrix substrate 101. The active matrix substrate 101
includes a transmissive substrate 1 made of a glass plate, or the
like, as well as a plurality of signal lines 2 and a plurality of
scanning lines 3 provided to cross each other via an insulation
film. The active matrix substrate 101 further includes TFTs 4 in
the vicinity of the intersection between the signal lines 2 and the
scanning lines 3 as switching elements, and pixel electrodes 5. A
display region is defined by the plurality of pixel electrodes 5
arranged in a matrix. Each of the pixel electrodes 5 is connected
to a corresponding TFT 4. The signal lines 2 and the scanning lines
3 extend beyond the display region. A signal input terminal 6 is
provided at one end of each signal line 2 while a signal input
terminal 7 is provided at one end of each scanning line 3.
Furthermore, a short-circuiting line 8 is formed around the display
region. Until a certain point in the production process, the
short-circuiting line 8 is connected to both ends of the signal
lines 2 and the scanning lines 3.
[0008] FIG. 8 is a plan view illustrating another conventional
active matrix substrate 111. Elements in FIG. 8 which are
functionally the same as those in FIG. 7 are denoted by the same
reference numerals and will not be further described. In FIG. 8,
for simplicity, elements provided inside a display region 20 and
some of the lines and terminals provided around the display region
20 are not shown. In this active matrix substrate, the
short-circuiting line 8 is connected to one end of each signal line
2 at which the signal input terminal 6 is not provided and to one
end of each scanning line 3 at which the signal input terminal 7 is
not provided.
[0009] Such an active matrix substrate is attached to a counter
substrate having a transmissive substrate and counter electrodes
provided thereon. Then, a liquid crystal material is injected
between the substrates, thereby completing the liquid crystal
display panel. Herein, the panel cannot be driven with the signal
lines 2 and the scanning lines 3 being short-circuited by the
short-circuiting line 8. Therefore, the short circuit is removed
before the liquid crystal panel is completed by severing the
substrate 111 along a severance line 10.
[0010] As described above, the short-circuiting line 8 is provided
to connect the signal lines 2 and the scanning lines 3 to one
another, whereby the signal lines 2 and the scanning lines 3 are
always kept at the same potential. Thus, it is possible to prevent
the deterioration of the TFT characteristics and the insulation
breakdown between the signal lines 2 and the scanning lines 3, even
if an electrostatic charge is applied during a step of producing
the liquid crystal display panel.
[0011] However, in the structures illustrated in FIGS. 7 and 8, the
signal lines 2 and the scanning lines 3 are electrically isolated
from one another after the active matrix substrate is severed.
Thus, it is not possible to prevent the deterioration of the TFT
characteristics and the insulation breakdown between the signal
lines 2 and the scanning lines 3 due to an electrostatic charge
generated during steps after the severance step. Moreover, even
after the liquid crystal display panel is completed, the TFT, whose
characteristics can deteriorate even by an applied voltage of about
100 V, is always subject to an influence of an electrostatic charge
until it is incorporated in a shield case. For example, the TFT is
subject to the influence of an electrostatic charge during steps of
connecting drivers to the panel, attaching a polarizer thereto, and
incorporating the panel into a shield case. Thus, it is very
difficult in practice to completely prevent an electrostatic charge
of such a magnitude from being generated and influencing the
TFTs.
[0012] Furthermore, in the structure illustrated in FIG. 7, after
the severance, each edge of the substrate 101 includes severed
sections of the signal lines 2 or the scanning lines 3. In the
structure illustrated in FIG. 8, two edges of the counter substrate
(e.g., the upper and left edges, as in FIG. 8), along which the
signal input terminals 6 or 7 are not provided, will have severed
sections of either the signal lines 2 or the signal lines 3 after
the severance. An electrostatic charge entering the panel through
these severed sections often causes a problem, thereby
significantly lowering the product yield.
[0013] Moreover, in the structures illustrated in FIGS. 7 and 8,
until the active matrix substrate is severed and the short circuit
by the short-circuiting line 8 is removed, all the signal lines 2
and the scanning lines 3 are short-circuited, whereby it is not
possible to conduct a test for detecting a short circuit between
the signal lines 2 and the scanning lines 3 or for detecting a
disconnection of the lines.
[0014] In view of this, another type of conventional active matrix
substrate 121 is known, which includes elements 12 and inner
short-circuiting line 13, as shown in FIG. 9.
[0015] FIG. 9 shows an equivalent circuit of such a conventional
active matrix substrate 121. Elements in FIG. 9 which are
functionally the same as those in FIG. 7 are denoted by the same
reference numerals and will not be further described. In this
active matrix substrate 121, the inner short-circuiting line 13 is
separately provided inside the short-circuiting line 8, where the
signal lines 2 and the scanning lines 3 are connected to the inner
short-circuiting line 13 via the elements 12. As the element 12, a
high resistance element made of a semiconductor thin film, or the
like, or a non-linear element which exhibits non-linear resistance
values for different applied voltages may be used.
[0016] In this structure, even after the active matrix substrate
121 is severed along the severance line 10 so as to disconnect the
signal lines 2 and the scanning lines 3 from the short-circuiting
line 8, there still remain connections of the signal lines 2 and
the scanning lines 3 with the inner short-circuiting line 13. Thus,
even when an electrostatic charge is applied during steps after the
substrate is severed, the electric charge is dispersed to all of
the signal lines 2 and the scanning lines 3 via the elements 12 and
the inner short-circuiting line 13. Thus, it is possible to prevent
the deterioration of the TFT characteristics and the insulation
breakdown between the signal lines 2 and the scanning lines 3.
Herein, the connection resistance between the signal lines 2 and
the inner short-circuiting line 13, and between the scanning lines
3 and the inner short-circuiting line 13, is set to a value which
is sufficiently high to eliminate problems in conducting a test for
detecting a short circuit between the signal lines 2 and the
scanning lines 3, for detecting a disconnection of the lines during
the production process of the liquid crystal display panel, or in
actually driving the completed liquid crystal display panel.
[0017] In the conventional examples illustrated in FIGS. 7 and 8,
after the active matrix substrate is severed and the short circuit
between the signal and scanning lines 2 and 3 and the
short-circuiting line 8 is removed, each of the signal lines 2 and
the scanning lines 3 is electrically isolated from one another.
Therefore, when an electrostatic charge is applied after the
substrate is severed, it is not possible to prevent the
deterioration of the switching element characteristics and the
insulation breakdown between the signal lines 2 and the scanning
lines 3. Moreover, as the substrate edges have severed sections of
the signal lines 2 or the scanning lines 3, an electrostatic charge
entering the panel through these severed sections often causes a
problem. Furthermore, until the active matrix substrate is severed
and the short circuit by the short-circuiting line 8 is removed,
all the signal lines 2 and the scanning lines 3 are electrically
connected to each other, whereby it is not possible to conduct a
test for detecting a short circuit between the signal lines 2 and
the scanning lines 3 nor detect a disconnection of the lines.
[0018] In the conventional example illustrated in FIG. 9, the
elements 12 may be broken or the characteristics thereof may
deteriorate due to an applied electrostatic charge, so that leakage
might occur between the signal lines 2 and the scanning lines 3, or
non-uniformity may occur in the connection resistance between the
lines and the inner short-circuiting line 13, thus lowering the
display quality. Moreover, the resistance of the elements 12 is set
to a value which is sufficiently high to eliminate problems in
actually driving the display panel. Normally, the resistance value
of the elements 12 is set to be higher than the resistance value of
the signal lines 2 and the scanning lines 3 by an order of
magnitude or more. Therefore, when an electrostatic charge is
applied through the severed edge (such as C in FIG. 9), most of the
electric charge flows to the signal lines 2 or the scanning lines 3
due to the resistance difference. Thus, substantially no electric
charge is dispersed to the inner short-circuiting line 13 via the
elements 12, whereby the characteristics of the TFTs 4 connected to
the signal lines 2 or the scanning lines 3 may deteriorate, or the
insulation between the lines may be broken.
SUMMARY OF THE INVENTION
[0019] According to one aspect of this invention, a display panel
includes: a first substrate and a second substrate opposing each
other with a display medium interposed therebetween; a plurality of
signal lines and a plurality of scanning lines provided on the
first substrate to cross each other and be insulated from each
other; and a plurality of pixel electrodes each provided in a
vicinity of an intersection between one of the plurality of signal
lines and one of the plurality of scanning lines so as to be
connected to the one of the plurality of signal lines and the one
of the plurality of scanning lines via a switching element, while
the plurality of pixel electrodes define a display region of the
display panel. At least one of each of the plurality of signal
lines and each of the plurality of scanning lines has a high
resistance portion proximate an end thereof outside the display
region. The high resistance portion is interposed at least
partially between the first substrate and the second substrate.
[0020] In one embodiment of the invention, the high resistance
portion is formed of a material including semiconductor, a metal,
and a metal oxide.
[0021] In another embodiment of the invention, the high resistance
portion is formed of a film having a specific resistance higher
than a specific resistance of a film which forms portions of the
plurality of signal lines and the plurality of the scanning lines
in the display region.
[0022] According to another aspect of this invention, a display
panel includes: a first substrate and a second substrate opposing
each other with a display medium interposed therebetween; a
plurality of signal lines and a plurality of scanning lines
provided on the first substrate to cross each other and be
insulated from each other; and a plurality of pixel electrodes each
provided in a vicinity of an intersection between one of the
plurality of signal lines and one of the plurality of scanning
lines so as to be connected to the one of the plurality of signal
lines and the one of the plurality of scanning lines via a
switching element, while the pixel electrodes define a display
region of the display panel. A first electrode, for inducing an
electrostatic charge applied to the display panel to the first
electrode, is provided outside the display region in a vicinity of
an end of at least one of each of the plurality of signal lines and
each of the plurality of scanning lines, the first electrode being
insulated from the plurality of signal lines and the plurality of
scanning lines.
[0023] In one embodiment of the invention, the first electrode is
electrically connected to a counter electrode on the second
substrate.
[0024] In another embodiment of the invention, the first electrode
is superimposed on, and insulated from, the plurality of signal
lines and the plurality of scanning lines.
[0025] In still another embodiment of the invention, the first
electrode is interposed between, and insulated from, two adjacent
ones of the plurality of signal lines and the plurality of scanning
lines.
[0026] In still another embodiment of the invention, the first
electrode is wider or larger in area than the portion of the
plurality of signal lines and the plurality of scanning lines near
an edge of the first substrate.
[0027] Hereinafter, the effect of the present invention will be
described.
[0028] In the present invention, the signal line and/or the
scanning line has a high resistance portion proximate the end
thereof outside the display region. Since the signal lines and the
scanning lines are connected to the short-circuiting line via the
high resistance portions, even if an electrostatic charge is
applied before the substrate is severed, the electrostatic charge
can be dispersed to the other lines via the high resistance portion
and the short-circuiting line, whereby the deterioration of the
switching element characteristics and the insulation breakdown
between the lines will not occur due to an electrostatic charge.
Moreover, since the resistance value of the high resistance portion
is sufficiently higher than the resistance value of the signal line
or the scanning line, it is possible to conduct a test for
detecting a disconnection of the signal lines and the scanning
lines or for detecting a leakage between these lines, with the
connection of these lines to the short-circuiting line still
intact.
[0029] Moreover, the high resistance portion is protruding from, or
interior to, an edge of the counter substrate, whereby when the
substrate is severed, part or all of the high resistance portion
remains between the severed edge of the substrate and the display
region. Thus, even when a static electric charge is applied during
steps after the substrate is severed, the voltage of the applied
electrostatic charge is lowered by the high resistance portion
before it reaches the display region, whereby the deterioration of
the switching element characteristics and the insulation breakdown
between the lines will not occur. Furthermore, since the high
resistance portion is located closer to the substrate edge than the
signal input terminals, the high resistance portion does not
influence a signal applied to the signal input terminals for
actually driving the display panel, even with the high resistance
portion remaining on the substrate after the display panel is
completed.
[0030] It is preferable that the high resistance portion is made of
a film having a specific resistance higher than a specific
resistance of a film which forms portions of the signal lines and
the scanning lines excluding the high resistance portion. Any film
such as a semiconductor film, a metal film or a metal oxide film
may be used for this purpose. Particularly, it is preferable that
the high resistance portion is formed of a material which forms the
active matrix substrate, whereby no additional production step is
required.
[0031] According to an alternative example of the present
invention, a discharge-inducing electrode is provided outside the
display region in the vicinity of the end of either or both of the
signal line and the scanning line so as to be insulated from these
lines. Therefore, even when an electrostatic charge is generated
around the display panel during a step of producing the display
panel or after the display panel is completed, the electrostatic
charge is discharged to the discharge-inducing electrode, whereby
the application of the electrostatic charge to the signal lines and
the scanning lines is suppressed. Thus, the deterioration of the
switching element characteristics and the insulation breakdown
between the lines will not occur.
[0032] When the discharge-inducing electrode is connected to the
counter electrode, the applied electrostatic charge is dispersed to
the entire display panel, whereby it is possible to avoid the
influence of the electrostatic charge.
[0033] The discharge-inducing electrode may be superimposed on, and
insulated from, the scanning lines and the signal lines, or it may
be interposed between, and insulated from, two adjacent signal
lines or two adjacent scanning lines. The discharge-inducing
electrode may further be provided outside the outermost lines so as
to be insulated from the outermost lines. In any case, since the
discharge-inducing electrode is electrically insulated from the
lines, the electrostatic charge applied to the discharge-inducing
electrode will not be applied to the scanning lines or the signal
lines.
[0034] The discharge-inducing electrode is preferably wider or
larger in area than the scanning lines or the signal lines at the
edge of the substrate, so that the electrostatic charge applied
around the display panel is more easily induced to the
discharge-inducing electrode.
[0035] Thus, the invention described herein has the advantage of
providing a display panel in which it is possible to prevent the
deterioration of the switching element characteristics and the
insulation breakdown between the lines due to an electrostatic
charge even after the substrate is severed.
[0036] This and other advantages of the present invention will
become apparent to those skilled in the art upon reading and
understanding the following detailed description with reference to
the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] FIG. 1 is a diagram illustrating an equivalent circuit of an
active matrix substrate in a display panel according to Example 1
of the present invention.
[0038] FIG. 2 is a partial enlarged view illustrating a display
panel according to Example 1 of the present invention.
[0039] FIG. 3 is a partial enlarged view illustrating a display
panel according to Example 2 of the present invention.
[0040] FIG. 4 is a partial enlarged view illustrating a display
panel according to Example 3 of the present invention.
[0041] FIG. 5 is a plan view illustrating an active matrix
substrate in a display panel according to Example 4 of the present
invention.
[0042] FIG. 6 is a plan view illustrating an active matrix
substrate in a display panel according to Example 5 of the present
invention.
[0043] FIG. 7 is a diagram illustrating an equivalent circuit of a
conventional active matrix substrate.
[0044] FIG. 8 is a diagram illustrating an equivalent circuit of
another conventional active matrix substrate.
[0045] FIG. 9 is a diagram illustrating an equivalent circuit of
still another conventional active matrix substrate.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0046] Hereinafter, the present invention will be described by way
of illustrative examples with reference to the accompanying
figures. In the figures for illustrating the examples of the
present invention, elements which are functionally the same as
those in the conventional examples are denoted by the same
reference numerals.
EXAMPLE 1
[0047] FIG. 1 shows an equivalent circuit of an active matrix
substrate 11 in a display panel according to Example 1 of the
present invention.
[0048] The active matrix substratell includes a transmissive
substrate 1 made of a glass plate, or the like, as well as a
plurality of signal lines 2 and a plurality of scanning lines 3
provided to cross each other via an insulation film (not shown).
The active matrix substrate 11 further includes TFTs 4 in the
vicinity of the intersection between the signal lines 2 and the
scanning lines 3 as switching elements, and pixel electrodes 5. A
display region 20 is defined by the plurality of pixel electrodes 5
provided in a matrix arrangement. Each of the pixel electrodes 5 is
connected to a corresponding TFT 4. The signal lines 2 and the
scanning lines 3 extend beyond the display region 20. A signal
input terminal 6 is provided at one end of the signal line 2 while
a signal input terminal 7 is provided at one end of the scanning
line 3. Each of the pixel electrodes 5 is provided with a signal
from the corresponding signal line 2 via the TFT 4, which is
switched by a signal from the corresponding scanning line 3.
[0049] Furthermore, a short-circuiting line 8 is formed around the
display region 20. The short-circuiting line 8 is connected to high
resistance portions 9 provided at both ends of the signal lines 2
and the scanning lines 3. The high resistance portions 9 can be
formed simultaneously with the TFTs 4 using, for example, an
n.sup.+ a-Si semiconductor film, which forms the TFTs 4. The
specific resistance of n.sup.+ a-Si is usually about several tens
.OMEGA.cm, and the thickness thereof is about several hundred
angstroms. When the specific resistance of n.sup.+ a-Si is about
100 M.OMEGA./.quadrature., the width of the high resistance
portions 9 about 100 .mu.m, and the length thereof about 10 .mu.m,
then, the connection resistance between the signal lines 2 or the
scanning lines 3 and the short-circuiting line 8 is about 10
M.OMEGA..
[0050] To complete a display panel, the active matrix substrate 11
is attached to a counter substrate (not shown) having a
transmissive substrate and planar counter electrodes provided
thereon. FIG. 2 is an enlarged view showing a portion of the
display panel corresponding to the upper portion of the active
matrix substrate 11 of FIG. 2, before the active matrix substrate
is severed. After the attachment of the active matrix substrate 11
and the counter substrate, the substrate 11 is severed along a
severance line 10, as shown in FIGS. 1 and 2, so as to remove the
portion on which the short-circuiting line 8 is provided. A part of
the high resistance portion 9 remains at both ends of the signal
lines 2 (and the scanning lines 3). In FIGS. 2, 3 and 4, reference
numeral 31 denotes an edge of the substrate 11 before it is
severed, and reference numeral 32 denotes an edge of the counter
substrate.
[0051] As shown in FIG. 2, the edge 32 of the counter substrate is
preferably positioned so that the counter substrate completely
covers the signal line portions 2a (and the scanning line
portions), while it does not completely cover the high resistance
portions 9. Then, the gap between the active matrix substrate and
the counter substrate is filled with a liquid crystal material,
thereby completing the liquid crystal display panel.
[0052] In the display panel, all the signal lines 2 and the
scanning lines 3 are connected to the short-circuiting line 8 via
the high resistance portions 9, until the active matrix substrate
11 is severed. Therefore, even when an electrostatic charge is
generated during steps before the substrate 11 is severed, the
applied electric charge is dispersed to all the lines via the high
resistance portions 9 and the short-circuiting line 8, whereby the
deterioration of the switching element characteristics and the
insulation breakdown between the lines will not occur. Moreover,
the line resistance value of the signal line portion 2a (and the
scanning line portion) is normally about 1 to several tens
k.OMEGA., and sufficiently lower than the resistance value of the
high resistance portion 9. Therefore, it is possible to conduct a
substrate test for detecting a disconnection of the lines or for
detecting a leakage between the lines.
[0053] During steps after the active matrix substrate 11 is
severed, the surface of the active matrix substrate 11 is covered
with the counter substrate except for the portion where the signal
input terminals 6 and 7 are formed. Therefore, a generated
electrostatic charge mostly enters the signal lines 2 and the
scanning lines 3 through the severed substrate edges (such as A in
FIGS. 1 and 2). However, since the high resistance portion 9 exists
between the signal line 2 and the severed edge and between the
scanning line 3 and the severed edge, the voltage of the applied
electrostatic charge is lowered by the high resistance portion 9
before it reaches the display region 20, whereby the deterioration
of the switching element characteristics and the insulation
breakdown between the lines will not occur.
[0054] Moreover, since the high resistance portions 9 are located
closer to the substrate edge than the signal input terminals 6 and
7, the high resistance portions 9 do not influence signals applied
to the signal input terminals 6 and 7 for actually driving the
display panel. Furthermore, since the signal lines 2 and the
scanning lines 3 are not connected to each other, unlike the
conventional example illustrated in FIG. 9, leakage between lines
due to an electrostatic charge applied to the elements 12 (see FIG.
9) which connects the lines to each other will not occur, and
accordingly a display non-uniformity due to a slight leakage will
not occur.
[0055] In the present example, the severance line 10 of the active
matrix substrate 11 is positioned so as to remove the portion of
the substrate 11 on which the high resistance portions 9 are
provided. However, the severance line 10 may be at any other
position so long as part or all of each of the high resistance
portions 9 remains between the severed edge of the substrate 11 and
the display region 20. In other words, the high resistance portions
9 may be completely interposed between the active matrix substrate
11 and the counter substrate, or interposed only partially between
the active matrix substrate 11 and the counter substrate.
EXAMPLE 2
[0056] FIG. 3 is a partial enlarged view illustrating a display
panel according to Example 2 of the present invention. The view of
FIG. 3 corresponds to that of FIG. 2.
[0057] In the display panel of this example, the severance line 210
is positioned so as to cut off a portion of the short-circuiting
line 8 which is connected to the high resistance portions 9 of the
signal lines 2 and the scanning lines (not shown). After the
substrate is severed, a portion 8a of the short-circuiting line 8
is left in the peripheral region of the active matrix
substrate.
[0058] In the display panel, as in that of Example 1, all the
signal lines 2 and the scanning lines 3 are connected to the
short-circuiting line 8 via the high resistance portions 9 before
the active matrix substrate is severed. Therefore, even when an
electrostatic charge is generated, the applied electric charge is
dispersed to all the lines via the high resistance portions 9 and
the short-circuiting line 8, whereby the deterioration of the
switching element characteristics and the insulation breakdown
between the lines will not occur.
[0059] Moreover, during steps after the substrate is severed, the
applied electrostatic charge is dispersed to the signal lines 2 and
the scanning lines 3 via the portion of the short-circuiting line 8
remaining in the peripheral region of the active matrix substrate.
Therefore, the voltage of the applied electrostatic charge is
lowered by the high resistance portions 9 before it reaches the
display region.
[0060] Thus, the present example is further effective in preventing
the deterioration of the switching element characteristics and the
insulation breakdown between the lines due to an electrostatic
charge. In this case, however, the lines will be still connected
together via the high resistance portions 9 and the portion 8a of
the short-circuiting line 8 after the display panel is completed.
Therefore, it is necessary to set the connection resistance between
the adjacent signal lines (and the adjacent scanning lines) to a
predetermined value so as not to influence a driving signal for
actually driving the display panel.
EXAMPLE 3
[0061] FIG. 4 is a partial enlarged view illustrating a display
panel according to Example 3 of the present invention. The view of
FIG. 4 corresponds to that of FIG. 2.
[0062] After the substrate is severed, a portion 38a of the
short-circuiting line 38 is left in the peripheral region of the
active matrix substrate. The portion 38a of the short-circuiting
line 38 is connected to the end portions 2a of the signal lines 2
(or the end portions of the scanning lines 3) via the high
resistance portions 9.
[0063] In this display panel, a neck 38b is provided in the
short-circuiting line 38, and the severance line 10 is positioned
so that the active matrix substrate is severed in the neck 38b of
the short-circuiting line 38. After the substrate is severed, a
portion of the neck 38b of the short-circuiting line 38 is left in
the peripheral region of the active matrix substrate. The remaining
portion of the neck 38b is electrically connected to a plurality of
end portions 2a (three end portions 2a, in FIG. 4) of the signal
lines 2 (and the end portions of the scanning lines 3) via the high
resistance portions 9. In this case, the edge 32 of the counter
substrate is preferably positioned to cover at least a portion of
the neck 38b of the short-circuiting line 38.
[0064] In the display panel of Example 3, as in that of Example 1,
all the signal lines 2 and the scanning lines 3 are connected to
the short-circuiting line 38 via the high resistance portions 9
before the active matrix substrate is severed. Therefore, even when
an electrostatic charge is generated, the electric charge is
dispersed to all the lines via the high resistance portions 9 and
the short-circuiting line 38, whereby the deterioration of the
switching element characteristics and the insulation breakdown
between the lines will not occur.
[0065] Moreover, during steps after the substrate is severed, the
counter substrate covers at least a portion of the neck 38b of the
short-circuiting line 38, whereby an electrostatic charge is
applied only to the neck 38b (indicated at B in FIG. 4) after the
substrate is severed. Therefore, it is possible to considerably
reduce the problem caused by an electrostatic charge, as compared
to Examples 1 and 2. In Examples 2 and 3, the influence of an
electrostatic charge can be further reduced by connecting the
portion 38a of the short-circuiting line 38 that is left on the
panel after the severance to the counter electrode (not shown).
[0066] In Examples 1 to 3, a semiconductor film is used as the high
resistance portions 9. However, any film, such as a metal film or a
metal oxide film, can be used for this purpose as long as the film
has a specific resistance higher than that of the signal line
portion 2a or the scanning lines 3 in the display region 20 (see
FIG. 1). When a metal film is used as the high resistance portions
9, it is preferable, for example, to reduce the thickness of the
film or to increase the length to width ratio of the metal film so
as to increase the resistance value of the high resistance portions
9. Furthermore, a metal oxide film may be used as the high
resistance portions 9. When a semiconductor film, a metal film or a
metal oxide film which forms the active matrix substrate is used
for the high resistance portions 9, no additional production step
is required, thereby reducing the production cost.
[0067] Moreover, in Examples 1 to 3, the short-circuiting line 8
and 38 is formed around the display region so as to connect to the
high resistance portions 9 (provided at both ends of the signal
lines 2 and the scanning lines 3). However, it is also possible to
arrange the short-circuiting lines 8 and 38 in an L shape so as to
connect to the high resistance portions 9 (provided at one end of
the signal lines 2 and one end of the scanning lines 3). In such a
case, the edge 32 of the counter substrate is preferably positioned
so that the counter substrate completely covers the ends of the
lines which are not connected to the short-circuiting lines 8 and
38, so that no electrostatic charge is applied to the signal lines
2 and the scanning lines 3 by physical contact, or the like, after
the substrate is severed.
EXAMPLE 4
[0068] FIG. 5 is a plan view illustrating an active matrix
substrate 41 in a display panel according to Example 4 of the
present invention. In FIG. 5, for simplicity, elements provided
inside a display region 20 and some of the lines and terminals
provided around the display region 20 are not shown.
[0069] In this active matrix substrate 41, the short-circuiting
line 8 is connected to one end of each signal line 2 at which the
signal input terminal 6 is not provided, and to one end of each
scanning line 3 at which the signal input terminal 7 is not
provided. Moreover, as shown in FIG. 5, a discharge-inducing
electrode 15 is superimposed on the signal lines 2 and the scanning
lines 3 via an insulation film (not shown) along two sides (e.g.,
the upper and the left sides, as in FIG. 5) of the substrate 41
along which the signal input terminals 6 or 7 are not provided.
[0070] After the active matrix substrate 41 is attached to a
counter substrate (not shown) having counter electrodes provided
thereon, the gap between the substrates is filled with a liquid
crystal material, thereby completing the display panel. Before the
display panel is completed, the substrate 41 is severed along the
severance line 10 so as to remove the portion on which the
short-circuiting line 8 is provided. Thus, after the severance, the
ends of the signal lines 2 and the scanning lines 3 are covered
with the discharge-inducing electrode 15 along the two sides of the
substrate along which the signal input terminals 6 or 7 are not
provided.
[0071] Since the discharge-inducing electrode 15 covers the ends of
the signal lines 2 and the scanning lines 3, as described above,
most of the electrostatic charge discharged around the display
panel is induced to the discharge-inducing electrode 15. The
discharge-inducing electrode 15 is electrically insulated from the
signal lines 2 and the scanning lines 3. Therefore, no voltage is
applied to the TFT 4 formed at a location where the signal line 2
and the scanning line 3 cross each other, whereby the deterioration
of the TFT characteristics and the insulation breakdown between the
lines due to an electrostatic charge will not occur.
EXAMPLE 5
[0072] FIG. 6 is a plan view illustrating an active matrix
substrate 51 in a display panel according to Example 5 of the
present invention. In FIG. 6, for simplicity, elements provided
inside a display region 20 and some of the lines and terminals
provided around the display region 20 are not shown.
[0073] In this active matrix substrate 51, the short-circuiting
line 8 is connected to one end of each signal line 2 at which the
signal input terminal 6 is not provided and to one end of each
scanning line 3 at which the signal input terminal 7 is not
provided. Moreover, discharge-inducing electrodes 55 are provided
on both sides of, and spaced apart (thus insulated) from, each of
the signal lines 2 and the scanning lines 3, along two sides (e.g.,
the upper and the left sides, as in FIG. 6) of the substrate 51
along which the signal input terminals 6 or 7 are not provided.
[0074] After the active matrix substrate 51 is attached to a
counter substrate (not shown) having counter electrodes provided
thereon, the gap between the substrates is filled with a liquid
crystal material, thereby completing the display panel. Before the
display panel is completed, the substrate 51 is severed along the
severance line 10 so as to cut off the short-circuiting line 8.
Thus, after severance, the ends of the signal lines 2 and the
scanning lines 3 are each interposed by the discharge-inducing
electrodes 55 along the two sides of the substrate 51 along which
the signal input terminals 6 or 7 are not provided. The
discharge-inducing electrodes 55 may be omitted on the outer side
of the outermost signal lines 2 and scanning lines 3.
[0075] Since the discharge-inducing electrodes 55 interpose the
ends of the signal lines 2 and the scanning lines 3 while the width
of the discharge-inducing electrode 55 is wider than the width of
the signal line 2 or the width of the scanning line 3, as described
above, most of the electrostatic charge discharged around the
display panel is induced to the discharge-inducing electrodes 55.
The discharge-inducing electrodes 55 are electrically insulated
from the signal lines 2 and the scanning lines 3. Therefore, no
voltage is applied to the TFT 4 formed at a location where the
signal line 2 and the scanning line 3 cross each other, whereby the
deterioration of the TFT characteristics and the insulation
breakdown between the lines due to an electrostatic charge will not
occur.
[0076] Furthermore, in this display panel, the discharge-inducing
electrodes 55 are connected to counter electrodes (not shown) via a
common line 25, whereby a static electric charge can be dispersed
to the entire liquid crystal display panel through the counter
electrodes. Thus, the influence of an electrostatic charge can be
further reduced.
[0077] The shape of the discharge-inducing electrode 15 and 55 is
not limited to those illustrated in Examples 4 and 5. As long as
the discharge-inducing electrode 15 and 55 is formed in the
vicinity of the signal lines 2 and the scanning lines 3 using a
conductive material, the discharge-inducing electrodes 15 and 55
may have any shape corresponding to the connection pattern between
the signal lines 2 and the short-circuiting line 8 or the
connection pattern between the scanning lines 3 and the
short-circuiting line 8. Particularly, when the width or area of
the discharge-inducing electrode 15 and 55 at the substrate edge is
larger than the width or area of the lines 2 and 3 at the substrate
edge, an electrostatic charge can be effectively induced to the
discharge-inducing electrode 15 and 55. Moreover, when the
discharge-inducing electrode 15 and 55 is formed by using the same
material as the signal lines 2, the scanning lines 3 or the common
line 25 (in the case of Example 5), no additional production step
is required, thereby reducing the production cost.
[0078] As described in detail above, according to the present
invention, the scanning line and/or the signal line has a high
resistance portion proximate an end thereof outside the display
region. The active matrix substrate is severed so that the high
resistance portions may be completely interposed between the active
matrix substrate and the counter substrate, or interposed only
partially between the active matrix substrate and the counter
substrate. Therefore, it is possible to prevent the deterioration
of the switching element characteristics and the breakdown of the
insulation film between the lines. As a result, it is possible to
improve the production yield in all of the production steps before
and after the substrate is severed, and to produce a reliable
display panel.
[0079] Moreover, the resistance value of the high resistance
portions is sufficiently higher than that of the signal lines and
the scanning lines in the display region. Therefore, it is possible
to conduct a test for detecting a disconnection of the lines, or
for detecting a leakage between the lines, with the
short-circuiting line still being connected to the signal lines and
the scanning lines before the substrate is severed, thereby further
improving the production yield.
[0080] Furthermore, the high resistance portions are located closer
to the substrate edge than the signal input terminals. Thus, the
high resistance portions do not influence a signal applied to the
signal input terminals for actually driving the display panel, even
with the high resistance portions remaining on the substrate after
the display panel is completed. As a result, an image with a high
display quality is obtained.
[0081] Since the high resistance portions can be formed by using
the same material as that forming the active matrix substrate
(e.g., a semiconductor film, a metal film or an oxide film), no
additional production step is required, thereby reducing the
production cost.
[0082] Moreover, according to an alternative example of the present
invention, a discharge-inducing electrode is provided outside the
display region in the vicinity of the end of either or both of the
signal line and the scanning line. Therefore, even when an
electrostatic charge is generated around the display panel after
the display panel is completed, the electrostatic charge can be
induced to the discharge-inducing electrode, whereby it is possible
to prevent the electrostatic charge from being applied to the
signal lines or the scanning lines. Thus, it is possible to prevent
the deterioration of the switching element characteristics and the
insulation breakdown between the lines due to the electrostatic
charge.
[0083] Since the discharge-inducing electrode can be formed during
the step of forming the signal line or the scanning line, no
additional production step is required, thereby reducing the
production cost.
[0084] Various other modifications will be apparent to and can be
readily made by those skilled in the art without departing from the
scope and spirit of this invention. Accordingly, it is not intended
that the scope of the claims appended hereto be limited to the
description as set forth herein, but rather that the claims be
broadly construed.
* * * * *