Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1997-12-04
2001-01-09
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S139000, C349S151000
Reexamination Certificate
active
06172732
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a simple matrix or active matrix type liquid crystal display device and, more particularly, to a liquid crystal display device having lead-out wiring for connecting electrodes of the liquid crystal display device to driving elements.
BACKGROUND ART
For example, a liquid crystal display device comprises a liquid crystal display element (i.e., a liquid crystal display part, a liquid crystal display panel, an LCD or a liquid crystal display panel) in which two insulating substrates (hereinafter referred to as electrode substrates) made of transparent glass are superimposed on each other with a predetermined space therebetween in such a way that their surfaces on which display transparent pixel electrodes, an alignment film and so forth are formed are opposed to each other, both substrates are bonded to each other with a sealing material which is provided in a frame-like shape in a marginal portion between both substrates, a liquid crystal which is hermetically enclosed inside the sealing material between both substrates, the liquid crystal being charged inside the sealing material through a liquid crystal charging port provided in part of the sealing material, and polarizers are provided on the outside of the respective substrates; a backlight disposed below the liquid crystal display element and arranged to supply light to the liquid crystal display element; a driving circuit board for driving the liquid crystal display element, which is disposed outside the marginal portion of the liquid crystal display element; a frame-shaped body which is a molding for holding the above members; a metallic frame in which all the members are housed and a liquid crystal display window is formed; and other associated members.
The liquid crystal display element and the driving circuit board are electrically connected by, for example, a tape carrier package (hereinafter referred to as the TCP) equipped with a semiconductor integrated circuit chip for driving the liquid crystal display element. More specifically, a multiplicity of output terminals of the circuit board and a multiplicity of input terminals (input outer leads) of the TCP are connected by soldering, and a multiplicity of output terminals (output outer leads) of the TCP and a multiplicity of input terminals of the liquid crystal display element which are connected to the respective display electrodes are connected by means of an anisotropic conductive film (such input terminals are formed in an array at an end portion of a surface of one of the transparent glass substrates which constitute the liquid crystal display element, i.e., a surface of one of the electrode substrates). A multiplicity of input terminals of the semiconductor integrated circuit chip provided on the TCP are connected to a multiplicity of output inner leads of the TCP, while a multiplicity of output terminals of the semiconductor integrated circuit chip are connected to a multiplicity of inner leads of the TCP.
Such a liquid crystal display device is described in documents such as Japanese Patent Laid-Open No. 214E48/1986 and Japanese Utility Model Laid-Open No. 137E5/1990.
FIG. 24
is a schematic plan view showing essential portions of part of the wiring formed on an electrode substrate which constitutes a conventional liquid crystal display element, i.e., display electrodes, terminals for connection to electrodes of a TCP, and lead-out wiring for connecting both.
Display electrodes
46
which are made of transparent conductive film and are wired in parallel and constitute pixels are formed on a surface of an electrode substrate (
311
or
312
) which includes one of insulation substrates which are made of transparent glass and constitute a liquid crystal display element (no shown in FIG.
24
. See reference numeral
18
of FIG.
13
). Reference numerals
41
denote terminals (connecting electrodes) connected to the terminals (the output outer leads) of a TCP which is a driver element (not shown in FIG.
24
. See reference numeral
74
or
77
of FIG.
13
). Reference numerals
45
denote oblique straight wiring which are lead-out wiring which connects the display electrodes
46
and the terminals
41
, respectively. Reference numeral
40
denotes the center line of a terminal group which corresponds to a single TCP mounted on the electrode substrate
311
or
312
, and reference numeral
44
denotes a portion in which a sealing material is provided.
Conventionally, in the electrode substrate (
311
or
312
) which constitutes the liquid crystal display element, the array pitch of the electrodes of the TCP, i.e., the pitch of the terminals
41
connected to the terminals of the TCP is made narrower than the array pitch of the display electrodes
46
wired in parallel. Accordingly, the lead-out wiring which connect the display electrodes
46
and the terminals
41
are formed as the oblique straight wiring
45
. As shown in
FIG. 24
, in the case of the conventional lead-out wiring, both the angle of each conductor of the oblique straight wiring
45
(to the corresponding display electrode
46
or terminal
41
) and the width of each conductor of the oblique straight wiring
45
are adjusted so that the wiring resistances of the respective conductors of the lead-out wiring become equal. Such a pattern of lead-out wiring is called radial wiring.
Such prior art has the following problems.
One problem is that the area use efficiency (wiring efficiency) of the lead-out wiring on the electrode substrate
312
is low, their lengths are large and their wiring resistances are large. If the lead-out wiring are intended to be shortened, the width of each conductor of the lead-out wiring must be made narrow so as to provide a clearance (space) between each conductor of the lead-out wiring, so that the problem of an increase in wiring resistance occurs. Presently, the wiring resistances of lead-out wiring are, for example, 500 &OHgr; to 1 k&OHgr;, and are large compared to 500-700 &OHgr; which are the output resistances of driving semiconductor IC chips.
In addition, there is a vacant space between each group of the terminals
41
connected to the terminals (electrodes) of a plurality of TCPs which are installed in a line on an end portion of an electrode substrate, and since the terminals are made of, for example, ITO (indium-tin-oxide; Nesa) film, a difference in height between the area in which the terminals are present and the area in which the terminals are absent is produced by the film thickness of the terminals. The ITO film is as thick as 0.2-0.5 &mgr;m. This leads to the problem that during mass-production of liquid crystal display elements, such uneven shape is transferred to a rubbing roller for subjecting alignment treatment (rubbing) to an alignment film formed on the display electrodes, and if such rubbing roller is used to perform alignment treatment, uneven rubbing grooves are formed in the alignment film and the display quality is lowered.
Furthermore, since the oblique straight conductors
45
of the lead-out wiring are radially wired, the spaces between the conductors of the oblique straight wiring
45
becomes nonuniformly narrower from the display electrodes
46
toward the terminals
41
as shown in FIG.
24
. This leads to the problem that nonuniform shading occurs in a portion which originally needs to be uniformly black, within a so-called frame portion which is a non-lighting portion outside the display portion (a lighting portion) and inside a sealing material
44
(on the side where a liquid crystal is present) in a finished liquid crystal display element.
Furthermore, since the display electrodes
46
of the display portion are wired in parallel at equal intervals, the wiring density of the display electrodes
46
is uniform, whereas the oblique straight wiring conductors
45
which are radially wired as described above is not uniform in wiring density. In particular, a liquid crystal display device such as an STN-LCD (super twisted nematic LCD) which needs a high-precision gap (±0.1 &mgr;m)
Fujieda Masayoshi
Hayakawa Kouji
Hoshino Noboru
Imasaka Yoshiyuki
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Nguyen Dung
Sikes William L.
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