Electrode plate with two-layer metal electrodes including...

Details Electrode plate with two-layer metal electrodes including... Electrode plate with two-layer metal electrodes including...

1999-06-09

2001-02-06

Dudek, James A. (Department: 2871)

Liquid crystal cells, elements and systems

Particular structure

Having significant detail of cell structure only

C349S148000

Reexamination Certificate

active

06184964

ABSTRACT:

FIELD OF THE INVENTION AND RELATED ART
The present invention relates to an electrode plate, particularly an electrode plate provided with a specific metal electrode and a transparent electrode formed thereon and a production process of the electrode plate. The present invention also relates to a liquid crystal device including the electrode plate and a production process thereof.
In light-transmissive substrates of twisted nematic (TN)-type or super twisted nematic (STN)-type, there have generally been conventionally used ITO (indium tin oxide) films as transparent electrodes. However such ITO films constituting the transparent electrodes have a fairly high resistivity, so that they have caused a problem of a voltage waveform deformation (or distortion) due to electrical signal delay along with increases in size and resolution of a display area in recent years. Particularly, in liquid crystal devices using a ferroelectric liquid crystal, this problem has become more noticeable since such devices have included a cell structure having a smaller cell gap (e.g., 1-3 &mgr;m).
In order to solve the problem, it may be possible to increase the thickness of the transparent electrodes, but the formation of such thick transparent electrodes requires increased time and cost and results in a lower transparency of the electrodes.
In order to solve the above-mentioned problems, it has been proposed an electrode plate having structure in which a plurality of metal electrodes showing a low resistivity are formed along a plurality of transparent electrodes of a small thickness (as disclosed in Japanese Laid-Open Patent Application (JP-A 2-63019). The electrode plate includes metal electrodes embedded with a transparent insulating material so as to expose the metal pattern and transparent electrodes of, e.g., ITO film formed on the metal electrodes.
In producing an electrode plate having a structure as described above, it has been also proposed to use a transparent resin as the insulating material filling the gaps between the metal electrodes (JP-A 6-347810) as illustrated in
FIGS. 20 and 21
.
According to the proposed process, as shown in
FIG. 20A
, on a transparent smooth (or smoothening) mold substrate (hereinafter called “smooth plate”)
101
, a prescribed amount of a liquid resin of ultraviolet (UV)-curable resin
102
is placed dropwise by using a metering device of a dispenser (not shown). Then, as shown in
FIG. 20B
, a glass substrate
104
already provided with a pattern of ca. 1 &mgr;m-thick metal electrodes
103
is placed on the smooth plate having thereon the UV-curable resin
102
. The metal electrodes
103
may be formed on the glass substrate
104
by forming a metal film of, e.g., Cu (copper) through, e.g., sputtering and then effecting patterning of the metal film through a photolithographic process.
Then, as shown in
FIG. 21A
, the above-formed integrated structure (including the smooth plate
101
, the UV-curable resin
102
, the metal electrodes
103
and the glass substrate
104
) is incorporated in a press (pressing machine)
105
, followed by pressing thereof with the press
105
so as to ensure an intimate contact over the entire area between the smooth plate
101
and the glass substrate
104
. At this time, the smooth plate
101
and the glass substrate
104
are strongly and uniformly pressed by the press
105
so as to remove at least a portion of the UV-curable resin
102
present at the surface of the metal electrodes
103
, thus ensuring an electrical connection of the metal electrodes
103
with associated transparent electrodes of, e.g., ITO film formed in a later step by the contact therebetween.
Thereafter, the integrated structure is taken out from the press
105
and irradiated with UV rays
106
falling on the smooth plate
101
to cure the UV-curable resin
102
(FIG.
21
B), and then peeled or removed from the smooth plate
101
by a peeling device or mechanism (not shown) (FIGS.
21
C and
21
D).
Further, transparent electrodes
107
of ITO film are formed over the metal electrodes
103
and the UV-cured resin
102
filling the spacings between the metal electrodes
103
so as to be electrically connected with the metal electrodes
103
, thus preparing an electrode plate
100
embedding the metal electrodes
103
with the UV-cured resin
102
(FIG.
21
E).
The thus-prepared electrode plate
100
through the above-described conventional process may preferably include metal electrodes of Cu having a considerably low resistance of 2×10
−8
-10×10
−8
ohm.m. Such Cu-made metal electrodes have the advantages of a thin film thickness and inexpensive material cost, thus resulting in a most economical metal material.
In the case of using Cu as the material for metal electrodes
103
, however, the resultant metal electrodes
103
of Cu have a low adhesive force to the glass substrate
104
, so that a portion or all of the metal electrodes
13
are liable to be peeled or detached from the glass substrate
104
(i.e., remain on the smooth plate
101
) when the smooth plate
101
is removed from the above-mentioned integrated structure (consisting of the structural members
101
-
104
) in the peeling step as shown in
FIGS. 21C and 21D
. As a result, a yield of production of the electrode plate
100
is remarkably decreased in such a case.
Further, Cu constituting the metal electrodes
103
is a metal susceptible to oxidation, so that the resultant metal electrodes
103
are liable to fail to obtain a stable electrical connection with (or electrical conduction to) the transparent electrodes formed thereon due to surface oxidation of Cu in the step as shown in FIG.
21
E.
Further, in the above-described process for producing the electrode plate
100
, the metal electrodes
103
directly contacts the UV-curable resin
102
in the steps as shown in
FIGS. 21A and 21B
, thus being exposed to various solvents within and gaseous components generated by the UV-curable resin
102
.
With respect to this problem, when metal electrodes of a metal, such as Al (aluminum), capable of forming a strong passivation layer is used, the resultant metal electrodes are little accompanied with the problem in some cases. However, in order to obviate the voltage waveform distortion, in the case of using Cu having a lower resistivity than Al as the material for the metal electrodes
103
, the resultant metal electrodes
103
of Cu are exposed to the above-mentioned solvents and gaseous components to cause corrosion due to oxidation thereof since Cu does not form a passivation layer.
SUMMARY OF THE INVENTION
In view of the above-mentioned problems, a principal object of the present invention is to provide an electrode plate capable of improving adhesive properties (adhesiveness) between metal electrodes and a substrate having thereon the metal electrodes and providing a stable electrical conduction of the metal electrodes to transparent electrodes formed thereon, and a high-quality liquid crystal device including such an electrode plate.
Another object of the present invention is to provide processes for producing an electrode plate and a liquid crystal device as described above.
According to the present invention, there is provided an electrode plate, comprising: at least a light-transmissive substrate, a plurality of metal electrodes disposed on the light-transmission substrate and with spacings therebetween, and an insulating layer disposed at the spacings; wherein
each of the metal electrodes includes a first layer comprising a metal or alloy selected from the group consisting of titanium, chronium, molybdenum, tungsten, aluminum, tantalum and nickel, and a second layer comprising copper or silver disposed on the first layer.
According to the present invention, there is also provided an electrode plate, comprising: at least a light-transmissive substrate, a plurality of metal electrodes disposed on the light-transmissive substrate and with spacings therebetween, and an insulating layer disposed at the spacings; wherein
each of the metal electrodes includes a fi

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