Liquid crystal display panels having control lines with uniforms resistance

A liquid crystal display (LCD) panel includes a substrate, a plurality of parallel control lines on the substrate, and a bonding pad area on the substrate having a plurality of bonding pads therein. A respective one of a plurality of interconnecting conductors connect a respective bonding pad of the bonding pad area to a respective one of the plurality of parallel control lines, each of the plurality of interconnecting conductors having a uniform resistance. According to embodiments of the invention, an interconnecting conductor of the plurality of interconnecting conductors may include a material selected to provide the uniform resistance. The interconnecting conductor may include a first portion including a first material having a first resistivity and a second portion including a second material having a second resistivity different from the first resistivity. The first and second portions may have respective first and second lengths selected to provide the uniform resistance. According to other embodiments, an interconnecting conductor of the plurality of interconnecting conductors may have a width selected to provide the uniform resistance. In one embodiment, the plurality of interconnecting conductors have a resistivity per unit length associated therewith and extend from the bonding pad area in a fanned configuration, with the resistivity of the interconnecting conductors increasing toward a medial portion of the fanned configuration. The width of the interconnecting conductors may decrease towards the medial portion of the fanned configuration to produce the desired resistivity. According to other embodiments, an interconnecting conductor of the plurality of interconnecting conductors has a length selected to provide the uniform resistance. In one embodiment, the interconnecting conductor has a serpentine portion to provide the desired length.

FIELD OF THE INVENTION 
The present invention relates to liquid crystal displays (LCDs), more 
particularly, to panels for LCDs. 
BACKGROUND OF THE INVENTION 
Typically, a liquid crystal display (LCD) panel includes a plurality of 
data lines and gate lines, the data lines being perpendicular to the gate 
lines. A plurality of pixel electrodes and a plurality of thin film 
transistors are formed in an active area in which the data lines and the 
gate lines typically cross each other at right angles. 
The data lines and the gate lines typically extend out of the active area 
for applying signals from an integrated circuit driver. A plurality of 
pads are formed in an out-lead bonding (OLB) pad area near the periphery 
of the active area. The OLB pad area typically includes a pad block which 
is used for mounting the integrated circuit driver. The pad block is 
typically connected to a fan-out block having a plurality of leads formed 
to connect the gate lines or data lines to the integrated circuit driver 
at a plurality of bonding sites. 
A conventional LCD panel is described in further detail with reference to 
FIGS. 1-3. As shown in FIG. 1, a conventional LCD panel includes a 
plurality of data lines 3 and gate lines 2 which cross each other at right 
angles on a display panel 1. The data 3 lines and the gate 2 lines cross 
each other in an active area B at which a plurality of pixel electrodes 
and thin film transistors are formed. 
The data lines 3 and the gate lines 2 extend outside of the active area B 
for connection to integrated circuit drivers. A plurality of pads are 
formed in pad areas 4 near the periphery of the active area B. In order to 
connect the gate lines 2 and the data lines 3 to the pads in the pad areas 
4, fan-out blocks 6 are formed in an OLB pad area C. The fan-out blocks 6 
include a plurality of leads 5 formed so that the extended gate and data 
lines 2, 3 may be gathered for connection to the pads in the pad areas 4. 
As illustrated in FIG. 2, a typical fan-out block 6 includes a plurality 
of leads 5 which run in straight lines and have equal thickness and width. 
The resistance of the lead in the conventional LCD may be calculated as 
follows: 
EQU R=.rho..times.L/S=(.rho..times.L)/(T.times.W), 
where .rho., L, S, T and W represent resistivity, length of the lead, cross 
sectional area of the lead, thickness of the lead and width of the lead, 
respectively. The resistivity .rho. typically is a constant which is 
dependent on the material from which the lead is fabricated. If the 
thickness and width of the lead are constant throughout the lead length L, 
the resistance R varies in proportion to the length L. 
According to the conventional configuration illustrated in FIGS. 1-2, the 
difference in resistance between leads 5 in the fan-out block 6 may 
generate time differences in signals being carried by the leads. 
Consequently, image quality of the display may be degraded due to time 
variation of the signals, especially in large-scale displays. For example, 
the difference of resistance between leads 5 of the fan-out block 6 
connected to a plurality of gate lines 2 may cause a time difference in 
switching on thin film transistors of the LCD elements, potentially 
degrading image quality. 
SUMMARY OF THE INVENTION 
In light of the foregoing, it is an object of the present invention to 
provide LCD panels which can provide higher image quality. 
This and other objects, features and advantages are provided according to 
the present invention by LCD panels in which conductors interconnecting 
parallel control lines of an LCD element array to bonding pads of a 
bonding pad area, e.g., lines of a fan-out block, are configured such that 
uniform resistance is provided between the bonding pads and the control 
lines, i.e., such that the interconnecting conductors provide 
approximately the same resistance between the associated bonding pads and 
control lines. In this manner, a uniform resistance may be provided 
between the bonding pad areas and LCD elements in a row of the LCD element 
array. Uniformity in resistance of the interconnecting conductors may be 
achieved by various techniques, including such measures as controlling the 
widths of the interconnecting conductors, including serpentine portions in 
the conductors to effectively increase the length of the conductors, and 
including portions of different materials having different resistivities 
in the conductors to provide the uniform resistance. Combinations of these 
resistance-controlling measures may also be employed. By providing 
uniformly resistive connections between the bonding pads and the parallel 
control lines, signal propagation speed among the control lines can be 
made more uniform. Accordingly, more uniform operation of the LCD element 
array may be achieved. 
In particular, according to the present invention, a liquid crystal display 
(LCD) panel includes a substrate, a plurality of parallel control lines on 
the substrate, and a bonding pad area on the substrate having a plurality 
of bonding pads therein. A respective one of a plurality of 
interconnecting conductors connects a respective bonding pad of the 
bonding pad area to a respective one of the plurality of parallel control 
lines, the plurality of interconnecting conductors providing a uniform 
resistance between the bonding pads and the control lines connected 
thereto. 
According to an aspect of the invention, an interconnecting conductor of 
the plurality of interconnecting conductors includes a material selected 
to provide the uniform resistance. The interconnecting conductor may 
include a first portion including a first material having a first 
resistivity and a second portion including a second material having a 
second resistivity different from the first resistivity. The first and 
second portions may have respective first and second lengths selected to 
provide the uniform resistance. At least one of the first and second 
portions may include a serpentine portion. 
According to another aspect, an interconnecting conductor of the plurality 
of interconnecting conductors has a width selected to provide the uniform 
resistance. In one embodiment, the plurality of interconnecting conductors 
have a resistivity per unit length associated therewith and extend from 
the bonding pad area in a fanned configuration, with the resistivity of 
the interconnecting conductors increasing toward a medial portion of the 
fanned configuration. The width of the interconnecting conductors may 
decrease towards the medial portion of the fanned configuration to produce 
the desired resistivity. 
According to another aspect, an interconnecting conductor of the plurality 
of interconnecting conductors has a length selected to provide the uniform 
resistance. In one embodiment, the interconnecting conductor has a 
serpentine portion to provide the desired length. The interconnecting 
conductor may have a first straight portion and a second serpentine 
portion. 
According to yet another aspect, an LCD panel includes a substrate, an 
array of LCD elements including a plurality of rows and columns, and a 
bonding pad area on the substrate having a plurality of bonding pads 
therein. A plurality of interconnecting conductors are formed on the 
substrate, a respective one of which connects a respective bonding pad to 
a respective LCD element of a row of LCD elements, each of the plurality 
of interconnecting conductors being configured to provide a uniform 
resistance between the bonding pad and the LCD element of the one row of 
LCD elements connected thereto.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
The present invention now will be described more fully hereinafter with 
reference to the accompanying drawings, in which embodiments of the 
invention are shown. This invention may, however, be embodied in many 
different forms and should not be construed as limited to the embodiments 
set forth herein; rather, these embodiments are provided so that this 
disclosure will be thorough and complete, and will fully convey the scope 
of the invention to those skilled in the art. In the drawings, the 
thickness of layers and regions are exaggerated for clarity, and like 
members refer to like elements throughout. In addition, as used herein, 
"uniform" resistance among a plurality of conductors means that the 
conductors each provide approximately the same resistance between the 
element connected thereto; conductors having a "uniform resistance" are 
not limited to conductors which have uniform resistivity along their 
length. 
As shown in FIG. 4, a liquid crystal display (LCD) panel according to an 
embodiment of the present invention includes a bonding pad area 4 
including a plurality of bonding pads connected to a plurality of parallel 
control lines 2, such as gate lines, data lines, or the like which extend 
from LCD elements in an active area B. A plurality of interconnecting 
conductors L1-Ln form a fan-out block 6' for connecting to a plurality of 
bonding pads in the bonding pad area 4, which in turn may be connected to 
an integrated circuit (IC) driver. For the illustrated embodiment, the 
interconnecting conductors 5' have equal thickness but differing widths 
such that the longest lead is the widest and the shortest lead, located a 
medial portion of the fan structure, is the narrowest. The widths and 
lengths of the leads are configured so as to give an equal ratio of length 
(L) to width (W), thus producing a uniform resistance R for all of the 
conductors L1-Ln, as graphically illustrated in FIG. 5. 
The embodiment illustrated in FIG. 6 addresses situations in which the 
difference of the length between the longest conductor and the shortest 
conductor may be excessive, such that in order to provide uniform 
resistance, the shortest conductor may become so narrow its fabrication 
may become difficult. Conductors 5' located near outer portions of the 
fan-out block 16 may have varying widths to produce an equal L/W ratio, 
while conductors 5" located nearer medial portions of the fan-out block 16 
may have a serpentine shape, e.g, a wavelike or ridged shape which 
effectively increases the length of these conductors. Those skilled in the 
art will appreciate that portions of the outer conductors 5' may also be 
shaped in a serpentine fashion. 
FIG. 7 illustrates yet another embodiment according to the present 
invention which utilizes another approach for producing uniform resistance 
in the interconnecting conductors. In the illustrated embodiment, the 
parallel control lines 2, e.g, gate lines or data lines, are connected to 
bonding pads of a bonding pad area 4 by a plurality of interconnecting 
conductors 10 in a fan-out block 26. Each of the conductors 10 includes a 
first portion formed of a first material TYPE I and a second portion 
formed of a second material TYPE II, the first and second materials having 
different resistivities. For example, the first material TYPE I may 
include chrome, while the second material TYPE II may include aluminum. 
The lengths of the first and second portions of a conductor 10 may be 
varied to control the resistance of the conductor 10. 
FIG. 8 illustrates an embodiment of the present invention in which the 
approaches for controlling conductor resistance illustrated in FIGS. 6 and 
7 are combined. An interconnecting conductor 20 of the fan-out block 36 
may include a serpentine portion of the first material TYPE I and a 
straight portion of the second material TYPE II. The lengths of the first 
and second portions and the resistance associated therewith may be related 
according to the following: 
EQU K.multidot.x+(a--x)=b 
EQU K.gtoreq.b/a1, a.gtoreq.x, 
where each of the symbols K, a, b, a1 and x represent a resistivity ratio 
of the first material TYPE I to the second material TYPE II, length of the 
conductor, length of the longest conductor, length of the shortest 
conductor and length of the first portion formed from the first material 
TYPE I. The lengths of the first and second portions of the conductors 20 
may be adjusted to achieve a uniform resistance for the conductors 20. 
In the drawings and specification, there have been disclosed typical 
embodiments of the invention and, although specific terms are employed, 
they are used in a generic and descriptive sense only and not for purposes 
of limitation, the scope of the invention being set forth in the following 
claims.