U.S. patent application number 11/907200 was filed with the patent office on 2008-06-19 for display drive circuit.
This patent application is currently assigned to Oki Electric Industry Co., Ltd.. Invention is credited to Atsushi Hirama.
Application Number | 20080143699 11/907200 |
Document ID | / |
Family ID | 39526556 |
Filed Date | 2008-06-19 |
United States Patent
Application |
20080143699 |
Kind Code |
A1 |
Hirama; Atsushi |
June 19, 2008 |
Display drive circuit
Abstract
A display drive circuit formed in a chip manufactured by a chip
on glass implementation, which is connected to lead lines formed on
a glass substrate, includes a rectangularly-shaped substrate, a
power supply line formed on the substrate, the line being elongated
along the longer side of the rectangular shaped substrate, a
plurality of output terminals formed on the rectangular shaped
substrate, the output terminal being disposed along the power
supply line, a plurality of bump electrodes, each of which connects
one of the output terminal to one of the lead lines, switches
disposed along the power supply line, each of which is connected
between the one of the output terminals and the power supply line,
a single power supply terminal, which is disposed near the middle
of the power supply line, being connected to the power supply
line.
Inventors: |
Hirama; Atsushi; (Chiba,
JP) |
Correspondence
Address: |
JUNICHI MIMURA;OKI AMERICA INC.
1101 14TH STREET, N.W., SUITE 555
WASHINGTON
DC
20005
US
|
Assignee: |
Oki Electric Industry Co.,
Ltd.
|
Family ID: |
39526556 |
Appl. No.: |
11/907200 |
Filed: |
October 10, 2007 |
Current U.S.
Class: |
345/206 |
Current CPC
Class: |
H01L 2224/17154
20130101; G09G 3/3266 20130101; G09G 3/3275 20130101; G09G
2300/0426 20130101; G09G 3/3208 20130101; H01L 2224/16 20130101;
G09G 3/3225 20130101; H01L 2924/01079 20130101; G09G 2320/0223
20130101; H01L 2924/12044 20130101; H01L 2924/19043 20130101; G09G
2330/021 20130101; H01L 27/3279 20130101; H01L 2924/12044 20130101;
G09G 2300/0408 20130101; H01L 2924/3011 20130101; H01L 21/76897
20130101; H01L 2224/05571 20130101; H01L 2924/00014 20130101; H01L
2224/05573 20130101; H01L 2224/0557 20130101; H01L 2924/00014
20130101; H01L 2224/0554 20130101; H01L 2924/00014 20130101; H01L
2224/05599 20130101; H01L 2924/00014 20130101; H01L 2224/0555
20130101; H01L 2924/00 20130101; H01L 2224/0556 20130101; G09G
2320/0233 20130101; G09G 3/3216 20130101 |
Class at
Publication: |
345/206 |
International
Class: |
G09G 5/00 20060101
G09G005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 15, 2006 |
JP |
2006-337902 |
Claims
1. A display drive circuit formed in a chip manufactured by a chip
on glass implementation, which is connected to lead lines formed on
a glass substrate, comprising: a rectangularly shaped substrate; a
power supply line formed on the substrate, the line being elongated
along the longer side of the rectangularly-shaped substrate; a
plurality of output terminals formed on the rectangularly-shaped
substrate, the output terminal being disposed along the power
supply line; a plurality of bump electrodes, each of which connects
one of the output terminal to one of the lead lines; switches
disposed along the power supply line, each of which is connected
between the one of the output terminals and the power supply line;
and a single power supply terminal, which is disposed near the
middle of the power supply line, being connected to the power
supply line.
2. A display drive circuit as claimed in claim 1, wherein the
single power supply terminal is disposed between the power supply
line and the longer side of the rectangularly-shaped substrate.
3. A display drive circuit as claimed in claim 1, wherein the power
supply line is a ground line supplying the ground electric
potential, and wherein the single power supply terminal is a ground
terminal supplying the ground electric potential.
4. A display drive circuit as claimed in claim 3, wherein the bump
electrodes are the first bump electrodes, further comprising a
second bump electrode, which is connected to the ground terminal,
wherein a drive current being reached to the ground terminal flows
to the ground.
5. display drive circuit formed in a chip manufactured by a chip on
glass implementation, which is connected to lead lines formed on a
glass substrate, comprising: a rectangularly-shaped substrate; a
power supply line formed on the substrate, the line being elongated
along the longer side of the rectangularly-shaped substrate; a
plurality of output terminals formed on the rectangularly-shaped
substrate, the output terminal being disposed along the power
supply line; a plurality of bump electrodes, each of which connects
one of the output terminal to one of the lead lines; switches
disposed along the power supply line, each of which is connected
between the one of the output terminals and the power supply line;
a first power supply terminal, which is disposed near the middle of
the power supply line, being connected to the power supply line a
second power supply terminal, which is connected to one end of the
power supply line; and a third power supply terminal, which is
connected to the other end of the power supply line, wherein a
contact resistance of the first power supply terminal is smaller
than that of both the second power supply terminal and the third
power supply terminal.
6. A display drive circuit as claimed in claim 5, wherein each of
the second and the third power supply terminals includes a
respective plurality of the power supply terminals.
7. A display drive circuit as claimed in claim 6, wherein the first
power supply terminals includes a plurality of the power supply
terminals.
8. A display drive circuit as claimed in claim 7, wherein a size of
each power supply terminal in the first power supply terminal is
the same as that of each power supply terminal in the first and
second power supply terminals, and wherein a number of the power
supply terminal in the first power supply terminal is greater than
that in both the second and the third power supply terminal.
9. A display drive circuit as claimed in claim 6, wherein a number
of the power supply terminal in the second power supply terminal is
different from that in the third power supply terminal.
10. A display drive circuit as claimed in claim 7, wherein each
pitch between the power supply terminals in the first power supply
terminal is greater than that in both the second and third power
supply terminals.
11. A display drive circuit as claimed in claim 5, wherein the
power supply line is a ground line supplying the ground electric
potential, and wherein each of the first, the second and the third
power supply terminal is a ground terminal supplying the ground
electric potential.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority benefit of Japanese
Patent Application No. 2006-337902, filed Dec. 15, 2006, the entire
disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to a display drive circuit for
operating a display device, which uses an organic
electroluminescent device (hereinafter called "an organic EL
device") or a light emitting diode (hereinafter called "an LED"),
and specifically, relates to a display drive circuit formed in a
chip manufactured by a Chip On Glass (hereinafter called "a COG")
implementation technology, which connects lead lines for a display
formed on a glass substrate by bonding.
[0004] 2. Description of the Related Art
[0005] FIG. 2A is a diagram showing the entire skeleton framework
of a display panel having an organic EL drive circuit formed on a
COG, and FIG. 2B is a sectional view taken on line 11-12 of FIG.
2A.
[0006] The display panel includes a nearly square-shaped glass
substrate 2, and a display area 10 displaying the images is located
in the center of the substrate 2. In the display area 10, a
plurality of data lines SEG and a plurality of scanning lines COM,
which are perpendicular to the data lines SEG, are formed. An
organic EL device 11 is formed at each intersection of the data
lines SEG and the scanning lines COM so that the organic EL devices
11 are arranged in a lattice-like manner. Both of the data lines
SEG and the scanning lines COM extend from the display area 10 to
an edge of the glass substrate 2 as lead lines. Each of the data
lines SEG and the scanning lines COM are formed of a transparent
conductive layer using ITO (indium Tin Oxide) for instance. The
transparent conductive layer using ITO has a large wiring
resistance, compared to that in a wiring layer made of cupper.
[0007] A display drive circuit according to the related art
includes a plurality of data line drive circuits 20-1 . . . 20-n
and a plurality of scanning line drive circuit 30-1 . . . 30-n.
Each of the data line drive circuits 20-1 . . . 20-n is formed on
one of the lead lines of the data lines SEG extending from the
display area 10, and is formed in an individual chip, which is
implemented by the COG method. Each data line drive circuit 20
includes switching elements such as transistors, which are operated
in response to image data for displaying the images, and which have
a function to supply a predetermined electric current to each of
the data lines SEG. Also provided on each of the lead lines of the
scanning lines COM extending from the display area 10 is a
respective one of the scanning line drive circuits 30-1 . . . 30-n,
each formed in an individual chip, which is implemented by the COG
method. Each scanning line drive circuit 30 includes switching
elements such as transistors, which are operated in response to
image data for displaying the images, and which have a function for
supplying ground electric potential (ex. 0 volt) to the scanning
lines SEG.
[0008] The glass substrate is equipped with unillustrated
electrical components, such as a control circuit, in an area around
the display area 10.
[0009] FIG. 3 is a skeletal circuit diagram in an area X of the
FIG. 2A, which is adjacent to one of the organic EL devices 11, and
in an area Y of the FIG. 2A, which is a part of one of the scanning
line drive circuit 30. FIG. 4A is a diagram showing a skeleton
framework of one of the scanning line drive circuit 30 shown in
FIG. 2A, and FIG. 4B is a sectional view taken on line 121-122 of
FIG. 4A.
[0010] As shown in FIG. 2A, the organic EL device is connected in a
forward direction between a data line SEG and a scanning line COM
that is perpendicular to the data line in the area X.
[0011] As shown in FIGS. 2A and 2B and FIGS. 4A and 4B, each of the
scanning line drive circuit 30 includes a rectangularly-shaped
substrate 31. An elongated ground line 32 having a width W and
length L is formed on the substrate 31 along the longer side of the
substrate 31. A plurality of output terminals 33-1 . . . 33-n are
disposed on the substrate 31 along one of the longer side of the
substrate 31, and a plurality of a switches 34-1 . . . 34-n, each
of which includes a transistor, are formed on the substrate 31
wherein each of the switches 34 is disposed between one of the
output terminals 33-1 . . . 33-n and the ground line 32. The
switches 34 are operated by the control circuit.
[0012] At both ends of the ground line 32, two ground terminals
35-1 and 35-2 are formed near the opposite longer side of the
substrate 31. Each output terminal 33 is connected to one of the
scanning lines through a bump electrode 36 formed thereon, and each
of the two ground terminals is grounded through another bump
electrode 36 formed thereon.
[0013] One of the organic EL devices 11 (for example the organic EL
device 11 illustrated in FIG. 2A) emits light in the following way.
Initially, the scanning line drive circuit 30-1, which connects the
organic EL device 11 to be eliminated, is connected to the ground
line 32 through the output terminal 33-1 and the switch 34-1 so
that the ground electric potential (0 volt) is supplied to the
scanning line COM connected to the organic EL devices 11. Then, the
drive current from the data line drive circuit 20-1 is supplied to
the data line SEG, which is connected to the organic EL devices 11.
Then, the drive current flows in the flowing order; the data line
SEG the organic EL device 11.fwdarw.the scanning line
COM.fwdarw.the output terminal 33-1.fwdarw.switch 34-1.fwdarw.the
ground line 32.fwdarw.the ground terminals 34-1 and 34-2. As a
result of the flow of the drive current as described above, the
organic EL device 11 emits light. The light intensity of the
organic EL device 11 depends on the value of the drive current.
[0014] Some technologies relating to the display panel having a
configuration similar to that described above are disclosed in the
following publications.
[0015] Reference 1: Japanese laid open patent 2002-151276
[0016] Reference 2: Japanese laid open patent 2003-131617
[0017] Reference 3: Japanese laid open patent 2004-206056
[0018] Reference 4: Japanese laid open patent 2005-144685
[0019] According to the reference 1, an EL display device with a
good balance between colors of EL elements and with a good balance
in emission intensity, which is capable of displaying brightly hued
images, is disclosed. According to the reference 2, EL drive
circuits, which are similar to the drive circuits of FIGS. 2A, 2B
and 3, are disclosed. According to the reference 3, EL drive
circuits, which suppress luminance unevenness and retain display
quality without enlarging a frame part, are disclosed. Further, the
reference 4 discloses line heads of the configuration without any
difference in the quantity of light emitted from a plurality of
light emitting elements, and an image forming apparatus using the
same.
[0020] The following problems are recognized in the display drive
circuit, for example, the scanning line drive circuits 30, in the
related art.
[0021] In such a scanning line drive circuits 30, as described
above, two ground terminals 34-1 and 34-2 are connected
respectively to the opposite ends of the ground line 32, and each
ground terminal 34-1 or 34-2, which are implemented by the COG
method, is grounded through a respective one of the bump electrodes
36.
[0022] Under the COG implementation, not only is high contact
resistance created, but also its deterioration is severe. With
consideration of the deterioration, the value of the contact
resistance varies greatly, such as from few .OMEGA. to few tens
.OMEGA.. The resistance value of the ground line 32 in the scanning
line drive circuits 30 is determined by the amount of an
electromigration. Thus, in the case that an active matrix organic
EL display panel as shown in FIGS. 4A and 4B is driven, it is
assumed that the maximum allowable current is required to be 1.0 A
of direct current. Here, the electromigration is the phenomenon
that occurs when some of the momentum of moving electrons is
transferred to nearby-activated ions. This causes the ions to move
from their original position.
[0023] In the case of the assumption described above, since the
maximum allowable current is generally set at 1 mA, the width W of
the ground line 32 is required to be a 1000 .mu.m when the length L
of the ground line 32 is set to be a 10,000 .mu.m. Since a sheet
resistance is 0.05.OMEGA./.quadrature., the resistance value of the
ground line 32 having the length L is calculated to be 0.5.OMEGA..
As a result, as shown as an arrow in FIG. 4A, the output electric
current, which is supplied from the left-end output terminal 33-1
to the ground line 32 through the switch 34-1, may flow to ground
through the right-end ground terminal 35-2 in the case that the
contact resistance at the ground terminal 35-1 is to be greater
than the sum of the resistance value of the ground line 32 and the
contact resistance at the ground terminal 35-2.
[0024] Further, the dispersion of the contact resistance can be
reduced by the size of the ground terminal 35-1 or 35-2. However,
if the sizes of the both ground terminals 35-1 and 35-2 are
reduced, it would be required to form a hundred ground terminals
near each ground terminal 35-1 and 35-2 to obtain the capacity to
pass the electric current to ground. As a result, the size of the
substrate 31 becomes larger because its longer side is further
elongated. This is a distant idea in view of the difficulty of its
implementation. Further, the width W of the ground line 32 may need
to be a 1000 .mu.m so that the shorter side of the substrate 31 is
also elongated. As a result, the total side of the scanning line
drive circuit becomes larger. This is a specific problem with
implementation using the COG method.
[0025] This problem cannot be solved by the technology disclosed in
the above-described references. For example, according to FIG. 1 of
the reference 1, the width of the wiring (107), which connects the
two terminals (105) acting as the supply terminals to the current
supply lines (104), is set to be a best value wherein two terminals
(105) correspond to the ground terminals 35-1 and 35-2 and the
current supply lines (104) correspond to the dale lines SEG and the
wirings (107) correspond to the ground line 32. If the width W of
the ground line 32 is set at the best value by using the technology
disclosed in the reference 1, the ground line 32 having a 1000
.mu.m width is required as described above. Thus, the shorter side
of the substrate 31 is elongated so that the problem is not
solved.
[0026] According to the reference 3, the width of the power supply
line supplying the power supply to the EL display panel is reduced
to half so that the area of the flame part can be reduced wherein
the area of the flame part corresponds to the area around the
display area 10 shown in FIG. 2A. The reason that the width of the
power supply line is reduced to half be that the power supply line
extends from the mounting terminal area (102) at both of its sides,
as shown in FIG. 4 of the reference 3. The technology disclosed in
the reference 3 corresponds to the description above in that the
width W of the ground line 32 is reduced to half by using two
ground terminals 35-1 and 35-2 connected at the both ends of the
ground line 32, as shown in FIG. 4A. Thus, the problem is not
solved.
[0027] The reference 4 does not consider any width of the wiring,
and the COG technology is not used. Thus, the teachings of
reference 4 cannot be combined with the related arts to solve the
problem.
[0028] As described above, the problem particularly occurring in
the COG technology cannot be solved by the technology disclosed in
the above-described references.
SUMMARY OF THE INVENTION
[0029] An objective of the invention is to solve the
above-described problem and to provide a display drive circuit,
whose operation does not depend on the variety of the contact
resistance value without making its substrate larger.
[0030] The objective is achieved by a display drive circuit formed
in a chip manufactured by a chip on glass implementation, which is
connected to lead lines formed on a glass substrate, comprising, a
rectangularly-shaped substrate, a power supply line formed on the
substrate, the line being elongated along the longer side of the
rectangularly-shaped substrate, a plurality of output terminals
formed on the rectangularly-shaped substrate, the output terminal
being disposed along the power supply line, a plurality of bump
electrodes, each of which connects one of the output terminal to
one of the lead lines, switches disposed along the power supply
line, each of which is connected between the one of the output
terminals and the power supply line, a single power supply
terminal, which is disposed near the middle of the power supply
line, being connected to the power supply line.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] The invention will be more particularly described with
reference to the accompanying drawings, in which:
[0032] FIG. 1A is a plan view showing a skeleton framework of a
display drive circuit, such as a scanning line drive circuit, used
in a display panel, according to a first embodiment;
[0033] FIG. 1B is a sectional view taken on line 121-122 of FIG.
1A;
[0034] FIG. 2A is an entire plan view of a configuration diagram
showing a skeleton framework of a display panel having an organic
EL drive circuit formed on a COG;
[0035] FIG. 2B is a sectional view taken on line 11-12 of FIG.
2A;
[0036] FIG. 3 is a skeletal circuit diagram in an area X of the
FIG. 2, which is adjacent to one of the organic EL devices 11 and
in an area Y of the FIG. 2, which is a part of one of the scanning
line drive circuit 30;
[0037] FIG. 4A is a plan view of a configuration diagram showing a
skeleton framework of one of the scanning line drive circuit 30
shown in FIG. 2;
[0038] FIG. 4B is a sectional view taken on line 121-122 of FIG.
4A;
[0039] FIG. 5A is a plan view showing a skeleton framework of a
display drive circuit, such as a scanning line drive circuit, used
in a display panel, according to a second embodiment;
[0040] FIG. 5B is a sectional view taken on line 131-132 of FIG.
5A;
[0041] FIG. 6 is an enlarged view showing a layout of the scanning
line drive circuit of FIG. 5A.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0042] The preferred embodiment of the invention is explained with
reference to drawings as follows. In each drawing, the same
reference numbers designate the same or similar components.
First Embodiment
[0043] FIG. 1A is a plan view showing a skeleton framework of a
display drive circuit, such as a scanning line drive circuit, used
in a display panel, according to a first embodiment and FIG. 1B is
a sectional view taken on line 121-122 of FIG. 1A.
[0044] As well as the display panel shown in FIGS. 2A and 2B, the
display panel 40 includes a nearly square-shaped glass substrate
41, and a display area 50 displaying the images is formed in the
center of the substrate 41. In the display area 50, a plurality of
data lines SEG and a plurality of scanning lines COM, which are
perpendicular to the data lines SEG, are formed. An organic EL
device 51 is formed at each intersection of the data lines SEG and
the scanning lines COM so that the organic EL devices 51 are
arranged in a lattice-like manner. Both of the data lines SEG and
the scanning lines COM extend from the display area 50 to an edge
of the glass substrate 41 as lead lines. Each of the data lines SEG
and the scanning lines COM are formed of a transparent conductive
layer using ITO (indium Tin Oxide) for instance. The transparent
conductive layer using ITO has large wiring resistance.
[0045] A display drive circuit includes a plurality of data line
drive circuit s 70 and a plurality of scanning line drive circuits
60. Each of the data line drive circuits 70 is formed on one of the
lead lines of the data lines SEG extending from the display area
50, and is formed in an individual chip, which is implemented by
the COG method. Each data line drive circuit 70 includes switching
elements such as transistors, which are operated in response to
image data for displaying the images, and which have a function to
supply a predetermined electric current to each of the data lines
SEG. Also provided on each of the lead lines of the scanning lines
COM extending from the display area 50 is a respective one the
scanning line drive circuits 60 formed in an individual chip, which
is implemented by the COG method. Each scanning line drive circuit
60 includes switching elements such as transistors, which are
operated in response to image data for displaying the images, and
which have a function for supplying ground electric potential (ex.
0 volt) to the scanning lines SEG.
[0046] Each of the scanning line drive circuit 30 includes a
rectangularly-shaped substrate 61. An elongated ground line 62
having a predetermined width W and a predetermined length L (ex.
10000 .mu.m), and having a resistance value R (ex. 0.5.OMEGA.) is
extended from one of the shorter side of the substrate 61 to the
opposite side on the substrate 61 along one of the longer side of
the substrate 61. A plurality of output terminals 63-1 . . . 63-n
are disposed regularly on the substrate 31 along another longer
side of the substrate 31, and a plurality of a switches 64-1 . . .
64-n, each of which includes a transistor, are formed on the
substrate 61 wherein each of the switches 34 is disposed between
one of the output terminals 63-1 . . . 33-n and the ground line 62.
The switches 34 are operated by an unillustrated control circuit
disposed in an area around the display area 50.
[0047] A single ground terminals 65 is disposed near the middle
location of the another longer side of the substrate 61 between
another longer side of the substrate 61 and the ground line 62, and
is connected to the ground line near its middle location. Thus, the
resistance value of the ground line 62 between the ground terminals
65 and the left end of the ground line 62 is R/2 (about
0.25.OMEGA.), and the resistance value of the ground line 62
between the ground terminals 65 and the right end of the ground
line 62 is also R/2 (about 0.25.OMEGA.). Each output terminal 63
are connected to one of the scanning lines COM through an AU bump
electrode 66 formed thereon, and the ground terminals 65 are
grounded through another AU bump electrode 66 formed thereon.
[0048] The operation of the display drive circuit of the first
embodiment is explained below. One of the organic EL devices 51
(for example the organic EL devices 51 illustrated in FIG. 1A)
emits light in the following way. Initially, the scanning line
drive circuit 60, which connects the organic EL device 51 to be
eliminated, is connected to the ground line 62 through the output
terminal 63-1 and the switch 64-1 so that the ground electric
potential (0 volt) is supplied to the scanning line COM connected
to the organic EL devices 51. Then, the drive current from the data
line drive circuit 70 is supplied to the data line SEG, which is
connected to the organic EL devices 51. Then, the drive current
flows in the flowing order; the data line SEG.fwdarw.the organic EL
device 51.fwdarw.the scanning line COM.fwdarw.the output terminal
63-1.fwdarw.switch 64-1.fwdarw.the ground line 64.fwdarw.the single
ground terminals 65. As a result of the flow of the drive current
described above, the organic EL device 51 emits light. The light
intensity of the organic EL device 51 depends on the value of the
drive current.
[0049] In the case that the switches 64-1 . . . 64-n are turned on
by the control circuit in series from the left (64-1) to the right
(64-n) illustrated in the FIG. 1A, the drive current from the
output terminals 63-1 . . . 63-n/2, which are located in the left
side, are flowed to the ground line 62 through the switches 64-1 .
. . 64-n/2. Then the drive current flows on the ground line 62 from
the left to the center, and then flows to the ground through the
single ground terminal 65. On the other hand, the drive current
output from the output terminals 63-(n/2+1) . . . 62-n at the right
side, flows to the ground line 62 through the switches 64-(n/2+1) .
. . 64-n respectively. Then the drive current flows on the ground
line 62 from the right to the center, and then flows to the ground
through the single ground terminal 65.
[0050] As described in the Background of the invention, as well as
the scanning line drive circuit 30 shown in FIG. 4, since large
contact resistance is formed on the COG implementation, when it is
assumed that the maximum allowable current is required to be 1.0 A
of direct current, the maximum allowable current is generally at 1
mA. Thus, under this assumption, when the width W of the ground
line 62 is set to be a 1000 .mu.m and the length L of the ground
line 62 is set to be a 10,000 .mu.m, the resistance value of the
ground line 32 having the length L is calculated 0.5.OMEGA. since a
sheet resistance is to be 0.05.OMEGA./.quadrature..
[0051] However, according to the first embodiment of the invention,
since the ground terminal 65 is located near the middle of the
ground line 62, and is connected to the ground line 62, the drive
current, which flows through the switches 64-1 . . . 64-n/2 located
in the left side, flows on the ground line 62 from its left to its
center, and then flows to the ground through the single ground
terminal 65 while the drive current, which flows through the
switches 64-(n/2+1) . . . 64-n/2 located in the right side, flows
on the ground line 62 from its right to its center, and then flows
to the ground through the single ground terminal 65. In other
words, the route of the drive current flowing on the ground line 62
does not depend on the dispersion of the contact resistance, and is
always the same. Again, in the scanning line drive circuit in the
related art shown in FIGS. 4A and 4B, the route of the drive
current flowing on the ground line 62 through the switch 34-1
depends on the contact resistances of the ground terminal, which
are determined accidentally in the COG process. In other words, in
a certain occasion (if the contact resistance of the ground
terminal 35-1 is smaller than the sum of the resistance values of
the ground line 32 and the ground terminal 35-2), the drive current
reached on the ground line 32 through the switch 34-1 flows to the
ground through the ground terminal 35-1. To the contrary, in
another certain occasion (if the contact resistance of the ground
terminal 35-1 is greater than the sum of the resistance values of
the ground line 32 and the ground terminal 35-2), the drive current
reached on the ground line 32 through the switch 34-1 flows to the
ground through the ground terminal 35-2. However, according to the
first embodiment of the invention, the drive current reached on the
ground line 62 through the switch 64-1 always flows to the ground
through the single ground terminal 65 so that the route of the
drive current from a certain switch is always the same. In the
first embodiment of the invention, the longest route on the ground
line 62 of the drive current is the half of the length of the
ground line 62 (L/2). Since the sheet resistance is to be
0.05.OMEGA./.quadrature., the resistance value R of the ground line
32 having the length L/2 is calculated 0.25.OMEGA.. As a result,
even if the width W of the ground line 62 can be reduced to half,
such as at a 500 mm, the electromigration may not occurs.
Accordingly, the length of the substrate 61 can be shorter at its
shorter side, and the total size of the scanning line drive circuit
60 can be miniaturized.
[0052] According to the first embodiment of the invention, at least
the following benefit can be expected. Since the single ground
terminal 65 is located near the middle of the ground line 62, and
is connected to the ground line 62, the length L of the ground line
62 is not changed while the width W of the ground line 62 is
reduced to half. As a result, the length of the substrate 61 can be
shorter at its shorter side, and the total size of the scanning
line drive circuit 60 can be miniaturized.
Second Embodiments
[0053] While a single ground terminal 65 is formed in the scanning
line drive circuit as shown in FIG. 1A in the first embodiment, a
first group of ground terminals are formed near the middle of a
ground line in a scanning line drive circuit, a second group of
ground terminals are formed at one end of the ground line, and a
third group of ground terminals are formed at the other end of the
ground line. The second embodiment is explained with reference to
FIGS. 5A, 5B and 6.
[0054] When the scanning line drive circuits 60 are arranged near
the display area 50, as well as the arrangement of the scanning
line drive circuits 30-1 . . . 30-n shown in FIG. 2, uniformity of
displaying the images may occur because of a differences of the
power supply impedance, which may be occur between the scanning
lines COM, each of which is connected to one adjacent scanning line
drive circuits. For example, a differences of the power supply
impedance may be occur between the scanning line COM disposed at
the most right in the most right side of the scanning line drive
circuit in the left and the scanning line COM disposed at the most
left in the most left side of the scanning line drive circuit,
which is next right to aforementioned scanning line drive circuit,
in the right. To eliminate the uniformity of displaying the images
occurred at the scanning lines having a difference of the power
supply impedance, the scanning line drive circuit according to the
second embodiment is composed as follows
[0055] FIG. 5A is a plan view showing a skeleton framework of a
display drive circuit, such as a scanning line drive circuit, used
in a display panel, and FIG. 5B is a sectional view taken on line
131-132 of FIG. 5A. FIG. 6 is an enlarged view showing a layout of
the scanning line drive circuit of FIG. 5A. In each drawing and in
the FIGS. 1A and 1B, the same reference numbers designate the same
or similar components.
[0056] As shown in FIG. 5A, a first group of an even number (l) of
ground terminals 65-1 is disposed near the middle of a ground line
62 in a scanning line drive circuit 60A, and each of the ground
terminals 65-1 of the first group is connected to the ground line
62. A second group of a number (m) of ground terminals 65-2 is
disposed at one end of the ground line 62 in the scanning line
drive circuit 60A, and each of the ground terminals 65-2 of the
second group is connected to the ground line 62. A third group of a
number (n) of ground terminals 65-3 is disposed at the other end of
the ground line 62 in the scanning line drive circuit 60A, and each
of the ground terminals 65-2 of the second group is connected to
the ground line 62. The numbers (m) and (n) could be the same, or
could be the different. Each of the ground terminals 65-1, 65-2 and
65-2 in the first through third group is grounded through an AU
bump electrode 66 formed thereon. Generally, the planar dimension
of each ground terminals 65-1, 65-2 and 65-3 is the same.
[0057] The number (l) of the ground terminals 65-1 is set to be
greater than that (m) of the ground terminals 65-2 or that (n) of
the ground terminals 65-2. For this reason, a total of planar
dimension of the ground terminals 65-1 of the first group is set to
be larger than a total of planar dimension of the ground terminals
65-2 of the second group or a total of planar dimension of the
ground terminals 65-3 of the third group. Thus, a sum of the
contact resistance of the ground terminals 65-1 of the first group,
each of which is connected in parallel, is smaller than that of the
ground terminals 65-2, each of which also is connected in parallel
or that of the ground terminals 65-3, each of which also is
connected in parallel.
[0058] Furthermore, as shown in FIG. 6, each of pitches p1 between
the ground terminals 65-1 of the first group is set to be greater
than each of pitches p2 between the ground terminals 65-2 of the
second group or each of the pitches p3 between the ground terminals
65-3 of the third group. The distances of the pitches (p2) and (p3)
could be the same, or could be the different.
[0059] The operation of the display drive circuit 60A of the second
embodiment is explained below. In the case that the switches 64-1 .
. . 64-n are turned on by the control circuit in series from the
left (64-1) to the right (64-n) illustrated in the FIG. 5A, the
drive current from the output terminals 63-1 . . . 63-n/2, which
are located in the left side, are flowed to the ground line 62
through the switches 64-1 . . . 64-n/2. Then a little part of the
drive current flows to the ground through the ground terminals 65-2
in the second group, and a large part of the drive current flows on
the ground line 62 from the left to the center, and then flows to
the ground through the ground terminals 65-1 of the first group, as
illustrated by an arrow in FIG. 5A. On the other hand, the drive
current output from the output terminals 63-(n/2+1) . . . 63-n at
the right side, flows to the ground line 62 through the switches
64-(n/2+1) . . . 64-n, respectively. Then a little part of the
drive current flows to the ground through the ground terminals 65-3
in the third group, and a large part of the drive current flows on
the ground line 62 from the left to the center, and then flows to
the ground through the ground terminals 65-1 of the first group, as
illustrated by an arrow in FIG. 5A
[0060] When a contact resistance value of each of the ground
terminals 65-1, 65-2 and 65-3 is the same, and is set at the range
between 1.OMEGA. (min) and 10.OMEGA. (max), and when the number (m)
of the ground terminals 65-2 is set at twenty (20), the number (n)
of the ground terminals 65-3 is also set at twenty (20), and the
number (l) of the ground terminals 65-1 is set at forty (40), each
sum of the contact resistance of the ground terminals 65-2 and 65-3
of the second and the third groups would be at the range between
0.1.OMEGA. (min) and 0.5.OMEGA. (max) and the sum of the contact
resistance of the ground terminals 65-1 of the first group would be
at the range between 0.05.OMEGA. (min) and 0.25.OMEGA. (max). Thus,
seventy percent (70%) of the drive current flows to the ground
through the ground terminals 65-1, and the rest (30%) of the drive
current flows to the ground through either of the ground terminals
65-2 or 65-3.
[0061] According to the second embodiment of the invention, since a
plurality of the ground terminals 65-2 and 65-3 are formed at the
both ends of the ground line 62 in addition to a plurality of the
ground terminals 65-1 near the middle of the ground line 62, it
could be reduce the differences of the power supply impedance,
which may occur between the scanning lines COM, each of which is
connected to one adjacent scanning line drive circuits. Accordingly
the uniformity of displaying the images at the scanning lines
having a difference of the power supply impedance can be
eliminated.
[0062] Furthermore, since a sum of the contact resistance of the
ground terminals 65-1 of the first group is smaller than that of
both the ground terminals 65-2 and the ground terminals 65-3, it
could cause a large part of the drive current to flow to the ground
through the ground terminals 65-1 located near the middle of the
ground line 62 so that almost the same benefit performed in the
first embodiment can be expected.
[0063] Moreover, since each of the pitches p1 between the ground
terminals 65-1 of the first group is set to be greater than each of
the pitches p2 between the ground terminals 65-2 of the second
group or each of the pitches p3 between the ground terminals 65-3
of the third group, degree of density of the ground terminals 65-1
is higher than that of the ground terminals 65-2 or that of the
ground terminals 65-3. Thus, the length of the scanning line drive
circuit 60A at its longer side can be suppressed to become further
longer. Furthermore, in the second embodiment of the invention,
since the size of the ground terminals 65-1, 65-2 and 65-3 are the
same, a plurality of the ground terminals 65-1 in the first group
is formed in order to excess the number (m) or (n) of the ground
terminals 65-2 and 65-3. However, a single ground terminal having a
planar dimension, which is larger than the total planar dimension
of either the ground terminals 65-2 or 65-3, may be disposed near
the middle of the ground line, and connects thereto.
[0064] While the invention has been described with reference to
illustrative embodiments, this description is not intended to be
construed in a limiting sense. Thus, shapes, size and physical
relationship of each component are roughly illustrated so the scope
of the invention should not be construed to be limited to them.
Further, to clarify the components of the invention, hatching is
partially omitted in the cross-sectional views. Moreover, the
numerical description in the embodiment described above is one of
the preferred examples in the preferred embodiment so that the
scope of the invention should not be construed to limit to them.
For example, in the display area 50 of the display panel 40 in the
FIG. 50, another circuit consignation can be employed. In the
embodiments, although the organic EL devices are used, other
display devices, such as a light emitting diode (LED) can be
employed to both embodiments. Further, the number (l) of the ground
terminals 65-1 and the numbers (m) and (n) of the ground terminals
65-2 and 65-3 may be set as a desired ratio. Moreover, in the
embodiments, although the scanning line drive circuits 60 and 60A
are explained for the sake of brevity, both embodiments can be
applied to another display drive circuit, such as the data line
drive circuit 70. For example, the ground line 62 can be replaced
with the power supply line, the switches 64 can be replace with
other switches, each having a different configuration, and the
ground terminal 65 can be replaced with an power supply
terminal.
[0065] Various other modifications of the illustrated embodiment
will be apparent to those skilled in the art on reference to this
description. Therefore, the appended claims are intended to cover
any such modifications or embodiments as fall within the true scope
of the invention.
* * * * *