Liquid crystal cells – elements and systems – Nominal manufacturing methods or post manufacturing...
Reexamination Certificate
1997-05-13
2001-03-27
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Nominal manufacturing methods or post manufacturing...
C349S106000, C349S111000, C349S158000
Reexamination Certificate
active
06208404
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a black matrix as well as a color filter for use in a color (flat) display such as a liquid crystal display, a thin film EL display or a field emitter display device to obtain a clear color display. More particularly, the invention relates to a method of manufacturing a color (flat) display, whereby the black matrix and the color filter may be prepared with an enhanced aperture rate and they as well as a cell gap controlling spacer arrangement can be prepared without a photo lithographic process that has hitherto had to be used despite of its complicated handling procedures.
BACKGROUND ART
An explanation will first be given of a typical color liquid crystal display device with reference to
FIG. 1
of the drawings attached hereto.
In
FIG. 1
, there is shown a pair of glass substrates
1
A and
1
B which are spaced apart from each other. Of them, the one glass plate
1
A has, outside thereof, a polarization plate
2
A bonded thereto and has, inside thereof, a number of color filter elements
3
G,
3
R and
3
B arranged for the three primary colors: red (R), green (G) and blue (B) of a light. Further, between a pair of adjacent color filter elements
3
and
3
, there is disposed a black matrix element or black stripe
4
that is designed to effect a glare protection and thus to obtain a clear color display. Of them, the black stripe is used exclusively for an electroplated color filter. Hence, numeral
4
here is used hereinafter in connection with the present invention to refer to a black matrix or black matrix element. Also, inside of the color filter
3
and the black matrix
4
mentioned above, there is disposed via a protective filter
5
a transparent electrode
6
A.
On the other hand, outside of the other
1
B of the above mentioned glass substrates, there is disposed via a polarization plate
2
B a light illuminating plate
7
that functions to provide a back light. In the vicinity of an end surface of the said light illuminating plate
7
, there is disposed a fluorescent lamp
8
that is adapted to cause the said light illuminating plate
7
to emit a light from over a surface thereof. Also, inside of the above mentioned glass substrate
1
B, there are so arranged a plurality of gates
10
as are covered with an insulating layer
9
. Further, inside of the said insulating layer
9
, there are arranged hydrogenated amorphous thin film transistors
11
, which are switching elements in opposition to the above mentioned gates
10
, in a manner such that they may be surrounded with their respective protective members
12
. And, inside of the above mentioned insulating layer
9
, there are arranged transparent electrodes
6
B, each associated with a said hydrogenated amorphous thin film transistor
11
for supplying the same with an electric current, respectively. It should also be noted that a liquid crystal LC is sealed in a tightly closed space between the above mentioned transparent electrodes
6
A and
6
B.
An explanation will now be given with respect the functions of the above mentioned black matrix
4
in a liquid crystal color display device as mentioned above. If the said black matrix
4
is held in the state in which the green color filter element
3
G is turned ON and the red color filter element
3
R and the blue color filter element
3
B which are adjacent thereto are each turned OFF, it will function in a manner such that the back light which is surface emitted from the said light illuminating plate
7
may be transmitted only through the said green color filter
3
G that is in the ON state and may not reach the said red and blue color filters
3
R and
3
B which are each in the OFF state.
And, the said black light matrix
4
is required to be composed of a material that is not only capable of shielding the back light but is of a low reflectivity to the back light. This is because if the green color filter element
3
G is in the ON state and the red and blue color filter elements
3
R and
3
B which are adjacent thereto are each in the OFF state, when the black matrix
4
has a high reflectivity to the back light a said back light that is reflected at the black matrix
4
will be incident to those hydrogenated amorphous thin film transistors
11
which are each in the OFF state, corresponding to the red and blue color filter elements
3
R and
3
B, and may possibly turn those transistors
11
each into the ON state.
By the way, from the standpoint of the requirement for a lower reflectivity, a resinous black may be used as a composition for a black matrix
4
to provide a reflectivity that is as low as 0.5%, and is thus found to be much superior to a metallic chromium composition having a reflectivity of 50% and to a low reflection chromium composition having a reflectivity of 30% or less. A black matrix
4
that is composed of the resinous black has the problem, however, that its optical density (OD) which is an index that is indicative of a light shielding performance for the back light is 2.3 which is lower than 4 or more with the metallic chromium composition or the low reflection chromium. For this reason, a low reflection composition in which a chromium oxide component is mounted on a metallic chromium component is now becoming a leading composition for a black matrix
4
.
An explanation will next be given with respect to a method of preparing a black matrix
4
. In a method other than an electroplating method, a black matrix
4
is first formed on a glass substrate
1
and thereafter each of the color filter elements
3
R,
3
G and
3
B are formed. While four methods of forming a color filter
3
have been employed up to present, a brief explanation will here be given of a pigment dispersion method and an electroplating method in the interest of convenience.
First, an explanation will be given of the pigment dispersion method.
Referring to
FIG. 2
, a glass substrate
1
on which a black matrix
4
is formed as shown at (a), is coated over its entire surface with a coloring resist
13
for a said red color filter element
3
R, as shown at (b), by the spin coating method or the roll coating method. Then, as shown at (c), the above mentioned coloring resist
13
is coated with a photo resist
14
by the spin coating method or the roll coating method. Further, as shown at (d) and (e), the layers
13
and
14
through a photo mask
15
are exposed to a light and developed to form red color filter elements
3
R.
Thereafter, by repeating a procedure as mentioned above with respect to a said green color filter element
3
G and a said blue color filter element
3
B, eventually the three color filter elements
3
R,
3
G and
3
B are formed.
Next, an explanation will be given of the electroplating method.
Referring to
FIG. 3
, a glass substrate
1
has an ITO (indium tin oxide) thin film
16
for electroplating formed thereon by the evaporation method, whereafter the said ITO thin film
16
is coated with a photo resist
14
, as shown at (a). Then, as shown at (b), (c) and (d), the layers
14
and
16
are exposed through a photo mask
15
to a light and developed, and etched to form a stripe of the said ITO thin film
16
. Thereafter, as shown at (e), the glass plate
1
on which the said stripe of the ITO thin film
16
is formed is immersed in an electroplating or electro-depositing liquid in which particles of a pigment for a said red color filter element
3
R are dispersed, and a positive voltage is applied between a pair of electrodes which are opposed to each other across the said ITO thin film
16
stripe so that those particles of the red pigment which have a particle size in the order of submicrons and are charged negative may electrolytically migrate towards the said ITO thin film
16
stripe charged positive and may then be electrolytically deposited on its surfaces. Subsequently, a said green color filter element
3
G and a said blue color filter element
3
B are electrolytically deposited by using respective electrolytic depositing or plating (i.e. electro-depositing or electroplating) liquids ther
Fujishima Akira
Hashimoto Kazuhito
Tomoyori Makoto
Duong Tai V.
Schreiber Donald E.
Sikes William L.
Tryonics Corporation
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