Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2000-12-14
2002-10-22
Dudek, James (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S140000, C349S111000
Reexamination Certificate
active
06469758
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a color filter for a liquid crystal display (LCD), and more particularly to a color filter that is adapted to be changeably used for a twisted nematic (TN) mode LCD and in a plane switching (IPS) mode LCD by forming a light-shielding layer at the rear side of a transparent substrate to improve surface morphology.
2. Description of the Related Art
Generally, a liquid crystal display (LCD) includes switching devices constituted by thin film transistors, each of which consists of a gate electrode, a gate insulating film, an active layer, an ohmic contact layer, source and drain electrodes, and a liquid crystal injected between a lower plate provided with pixel electrodes and an upper plate provided with color filters. The color filter includes red(R), green(G) and blue(B) unit filters on a transparent substrate, and a light-shielding layer for preventing deterioration of brightness and color purity among these unit filters. The color filter has a different configuration depending on the mode of the LCD. In the color filter used for the TN mode, a common electrode is formed on the unit filters. On the other hand, in the color filter used for the IPS mode, a protective film, instead of the common electrode, is formed on the unit filters and the light-shielding layer is made from only a resin so as to prevent an undesired affect to a horizontal electric field of the lower plate. Also, in the color filter used for the IPS mode, a transparent ground electrode for eliminating static electricity at the screen is formed at the rear surface of the transparent substrate, that is, at the surface in which the unit filters are not formed.
FIG. 1
is a sectional view showing a structural example of a conventional color filter for a TN mode LCD. Referring to
FIG. 1
, in the conventional color filter, a first light-shielding layer
13
formed of a metal oxide film and a second light-shielding layer
15
formed of a metal film are disposed in a lattice shape on a transparent substrate
11
. The first light-shielding layer
13
may be formed of a twofold film consisting of a metal oxide film and a metal nitride film. First, second and third filters
17
a,
17
b
and
17
c
for transmitting R, G and B color lights, respectively are formed at a portion in which the first and second light-shielding layers
13
and
15
on the transparent substrate
11
are not formed. The first, second and third filters
17
a,
17
b
and
17
c
are made from an acrylic resin or polyimide group resin dispersed with pigments, and is separately formed on the first and second light-shielding layers
13
and
15
to prevent color mixture.
A common electrode
19
made from a transparent conductive material such as an indium tin oxide (ITO), a tin oxide (TO) or an indium zinc oxide (IZO), etc. is formed on the first to third filters
17
a,
17
b
and
17
c.
The common electrode
19
allows the first to third filters
17
a,
17
b
and
17
c
to not contact a liquid crystal so as to prevent its damage.
FIG. 2
is a sectional view showing a structural example of a conventional color filter for an IPS mode LCD. Referring to
FIG. 2
, in the conventional color filter, a light-shielding layer
23
in which a resin dispersed with an electrically insulated black pigment has a lattice shape is formed on transparent substrate
21
. First, second and third filters
27
a,
27
b
and
27
c
for transmitting R, G and B color lights, respectively are formed at a portion in which the light-shielding layer
23
are not formed. The first, second and third filters
27
a,
27
b
and
27
c
are made from an acrylic resin or polyimide group resin dispersed with pigments, and is separately formed on the light-shielding layer
23
so as to prevent color mixture. In the case of forming the light-shielding layer
23
from a conductive material, a horizontal electric field generated from the lower plate causes drive problems due to noise generated upon drive control due to a derivative electric field generated by the conductive material.
A protective layer
25
is formed on the first to third filters
27
a,
27
b
and
27
c.
The protective layer
25
plays a role isolating the first to third filters
27
a,
27
b
and
27
c
from contact with a liquid crystal (to cause damage thereto), and is made from a transparent material having an insulating characteristic, such as polyimide. A ground electrode
29
is formed on the rear surface of the transparent substrate
21
, that is, on the surface in which the first to third filters
27
a,
27
b
and
27
c
are formed. The ground electrode
29
eliminates static electricity on a screen to prevent generation of domain stains, and is made from a transparent conductive material such as ITO, TO or IZO, etc.
However, the conventional color filter has a problem in that a step difference is generated at a portion where each of the filters overlaps by a thickness of the light-shielding layer, to cause deterioration in surface morphology. The TN mode color filter has a problem in that, when a stacked structure of a metal oxide film and a metal film is formed, pinholes are generated during the cleaning after generation of stripped particles in a continuous film formation process to thereby cause a light leakage phenomenon. The IPS mode color filter has a problem in that, since the light-shielding layer is made from only a resin and formed after formation of the ground electrode, a stain is generated due to its contact with a conveyer machine (e.g., a roller and a robot hand, etc.) upon formation of the ground electrode at the rear side of the transparent substrate, or an adhesion between the light-shielding layer and the transparent substrate is weakened to cause stain formation.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a color filter wherein a light-shielding layer is formed at the rear side of a transparent substrate to prevent deterioration of surface morphology.
A further object of the present invention is to provide a color filter that is capable of preventing light leakage caused by pinholes generated at a light-shielding layer.
A yet further object of the present invention is to provide a color filter that is capable of preventing stain formation caused by adhesion weakness between a light-shielding layer and a transparent substrate.
In order to achieve these and other objects of the invention, a color filter according to an embodiment of the present invention includes a light-shielding layer having a lattice shape formed from a metal material on a second surface of a transparent substrate having first and second surfaces; and first, second and third filters, being formed at a portion which does not correspond to the light-shielding layer on the first surface of the transparent substrate in such a manner so as to have a desired portion overlapped with the light-shielding layer, to transmit red, green and blue color lights, respectively.
REFERENCES:
patent: 4793691 (1988-12-01), Enomoto et al.
patent: 5568292 (1996-10-01), Kim
patent: 5-72559 (1993-03-01), None
Dudek James
L.G. Philips LCD Co., Ltd.
LandOfFree
Color filter does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Color filter, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Color filter will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2952670