Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2001-01-02
2003-11-18
Loke, Steven (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S435000, C257S437000, C438S048000
Reexamination Certificate
active
06649952
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a color filter for use in a flat panel display and, particularly, to a structure of a color filter for a liquid crystal display device.
2. Description of the Prior Art
As a color filter for a liquid crystal display device, there are two types, in one of which a color filter is formed on the side of an opposing substrate opposing to a Thin Film Transistor (referred to as “TFT”, hereinafter) substrate and in the other of which a color filter is formed on the side of the TFT substrate.
FIG. 1
is a cross section of the first example of a color filter to be formed on the side of an opposing substrate. As shown in
FIG. 1
, the color filter has a structure including a transparent substrate
41
, a black matrix
42
formed on the transparent substrate
41
by forming a lattice pattern with using photolithography, etc., a color layer
46
printed or covered by using photolithography with color materials such as dyes, organic pigments or inorganic pigments such that the color materials fill spaces between lattices of the black matrix
42
, a resin film layer
44
covering the color layer
46
and the black matrix
42
and a pixel electrode
45
formed on the resin film layer
44
.
FIG. 2
shows a cross section of the second example of the color filter to be formed on the side of the opposing substrate, which is disclosed in Japanese Patent Application Laid-open No. H5-119306 and may belong to the same category as that of the present invention. The second example, which is called as Color filter-On-TFT (COT), includes a transparent substrate
61
, a color layer
66
formed on the transparent substrate
61
, a resin film layer
64
formed on the color layer
66
, an upper titanium dioxide (TiO
2
) layer
73
formed on the resin film layer
64
and a pixel electrode
65
formed on the upper titanium dioxide layer
73
. The upper titanium dioxide layer
73
is formed for improving adhesion between the resin film layer
64
and the pixel electrode layer
65
.
FIG. 3
shows a cross section of the third example of the so-called color filter-on-TFT where a color filter is formed on the side of the TFT substrate, which is disclosed in EURO DISPLAY '99 LATE-NEWS PAPER P77-80. The third example includes a transparent substrate
81
, a TFT formed thereon, which is composed of a gate wiring
87
, a gate insulating film
88
, a semiconductor film
91
, a drain wiring
89
and a source wiring
90
and a protective insulating film
92
covering the TFT. As shown, an upper portion of the TFT except the protective insulating film
92
has a similar structure to that shown in FIG.
1
. That is, a color layer
86
having an opening portion above the semiconductor film
91
of the TFT is formed on the protective insulating film
92
and the opening portion is filled with a black matrix
82
. Further, the color layer
86
and a black matrix
82
are covered by a resin film layer
84
and a transparent pixel electrode
85
of ITO (Indium Tin Oxide).
However, in a liquid crystal display of such as IPS (In-Plane-Switched) system, which has no pixel electrode or the COT shown in
FIG. 2
, there is a possibility that a portion of the resin film layer
84
functioning as the over coat is exposed to the liquid crystal layer depending on a layout of the pixel electrode
85
.
If the resin film layer
84
is exposed partially, oxygen contained in the liquid crystal layer diffuses through the exposed portion into the color layer
86
. Oxygen molecules reached the color layer
86
are activated by excitation energy of external ultraviolet ray, so that color materials such as organic pigments used in the color layer are decomposed, resulting in color degradation.
Therefore, when a layer, which is formed above the color layer
86
in order to shut out oxygen molecules from the color layer
86
, does not cover the color layer
86
completely, i.e., some part of the layer is opened above the color layer
86
, some problems as mentioned above occurs in the conventional color filter substrate for liquid crystal display.
The structure including the upper titanium dioxide layer
73
such as shown in
FIG. 2
, which may block external ultraviolet ray, is known. In such color filter substrate, however, there is a possibility that the color layer
66
is degraded by activated oxygen dissolved in the resin film layer
64
.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a structure of a color filter which is not degraded by ultraviolet ray or oxygen on a substrate with a color filter.
In order to achieve the above object, the color filter according to the present invention includes a basic light shielding structure which blocks ultraviolet ray incident on a color layer formed on a substrate at least at the upper side of the color layer. The basic light shielding structure includes two types of light shielding structures, wherein the first light shielding structure blocking ultraviolet ray incident on the surface of the color layer at the upper side of the color layer by directly covering the surface of the color layer only at the upper side of the color layer and the second light shielding structure covering both on and below the color layer.
The first light shielding structure includes the color layer formed on the substrate and an upper light shielding layer, which directly covers the surface of the color layer at the upper side of the color layer.
The second light shielding structure includes an upper light shielding layer formed on the color layer and a lower light shielding layer formed below the color layer, blocking ultraviolet ray by both of the upper light shielding layer and the lower light shielding layer from the color layer. Furthermore, the upper light shielding layer covers the surface of the color layer at the upper side of the color layer, and more concretely covers directly the surface of the color layer at the upper side of the color layer.
The color filter according to the second light shielding structure of the present invention includes a substrate, a color layer on the substrate, a gate electrode and a semiconductor layer which composes a channel region of a TFT between the substrate and the color layer, the color layer being formed above the TFT, an upper light shielding layer covering the color layer. The color layer includes an opening area above the channel region of the TFT. The color filter further includes a black matrix layer formed between the TFT and the upper light shielding layer. The black matrix layer covers at least the opening area of the color layer and locates above the channel region of the TFT.
The light shielding structure of the color filter includes a titanium dioxide layer.
REFERENCES:
patent: 5321250 (1994-06-01), Tajima
patent: 5835177 (1998-11-01), Dohjo et al.
patent: 6078372 (2000-06-01), Kim
patent: 6137552 (2000-10-01), Yanai
patent: A 60-247202 (1985-12-01), None
patent: A 4-110902 (1992-04-01), None
patent: 5-119306 (1993-05-01), None
patent: A 9-5733 (1997-01-01), None
patent: A 10-206888 (1998-08-01), None
M. Maruyama et al., “An Ultra High Resolution TFT LCD Having a New Color Filter Structure”, EURO Display 1999 Late-News Paper, pp 77-80.
Gebremariam Samuel
Loke Steven
NEC LCD Technologies Ltd.
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