Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2003-10-15
2004-09-07
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S149000
Reexamination Certificate
active
06788380
ABSTRACT:
BACKGROUND OF THE INVENTION
1) Field of the Invention
This invention pertains to the field of liquid crystal display (LCD) devices, such as liquid crystal on silicon (LCOS) devices, and more particularly to a structure for such a device providing for uniform spacers.
2) Description of the Related Art
Reflective LCD devices are well known. Examples of such devices, and in particular active matrix devices, are shown in U.S. Pat. Nos. 6,023,309 and 6,052,165. With reference to the following description, familiarity with conventional features of such devices will be assumed, so that only features bearing on the present invention will be described.
FIG. 1
shows a portion of a typical prior-art reflective LCD device
100
. The reflective LCD device
100
may generally be divided into a pixel region
100
a
(active region) and a peripheral region
100
b
. The pixel region
100
a
includes an array of pixel elements and the peripheral region
100
b
includes driver circuits
105
for supplying driving signals to each of the pixel elements.
The LCD device
100
comprises, in relevant part, a silicon substrate
110
, an insulating layer
112
, a liquid crystal layer
114
a transparent electrode
116
, such as indium-tin-oxide (ITO), and a transparent (e.g., glass) layer
118
. A reflective mirror (pixel) metal layer
120
is provided beneath the liquid crystal layer
114
on the insulating layer
112
. The mirror metal layer
120
includes a plurality of individual reflective pixel electrodes
120
a
in the pixel region
100
a
, and a substantially continuous peripheral portion
120
b
formed in the peripheral region
100
b
of the LCD device
200
. Light transmissive regions
122
are located between the pixel electrodes
120
a.
Also provided in the insulating layer
112
and between the mirror metal layer
120
and the substrate
110
are a light shield metal layer
124
and routing metal layers,
128
and
130
. In the pixel region
100
a
, the metal layers
128
and
130
form mutually-orthogonal row and column lines, which may be connected to gate and source electrodes of MOS transistors (not shown in
FIG. 1
) for pixel elements fabricated in the underlying substrate
110
. In the peripheral region
100
b
, the metal layers
128
and
130
form signal routing lines used for routing various signals of the driver circuits. Also, metal plugs or vias
132
are provided for connecting various portions of the light shield metal layer
124
and the third and fourth metal layers
128
,
130
with each other.
The metal layer
124
is provided to prevent light entering the device, such as through the transmissive regions
122
between the pixel electrodes
120
a
, from reaching the substrate
110
where it might induce leakage currents on otherwise interfere with proper device operation. While portions of metal layers
128
or
130
may incidentally block a small portion of light entering the device, the structure of
FIG. 1
requires a separate metal layer
124
to be dedicated to provide the required degree of light blocking in the peripheral region
100
b.
A plurality of spacers or pillars are provided for supporting the transparent layer
118
and providing a gap for the liquid crystal layer
114
. In the pixel region
100
a
, the spacers
134
a
are placed directly on the insulating layer
112
. In the peripheral region
100
b
, spacers
134
b
are provided on the peripheral portion
120
b
of the mirror metal layer
120
.
In order to maintain a uniform liquid crystal cell gap, it becomes necessary for the spacers in the peripheral region
100
b
to have a height that is the same as the spacers in the pixel region
100
a
. However, the spacers
134
b
formed on the mirror metal layer
120
in the peripheral region
100
b
are taller than the spacers
134
a
formed on the insulating layer
112
in the pixel region
100
a
because of the extra height of the metal layer
120
, thus producing a non-uniform display.
Accordingly, it would be desirable to provide a liquid crystal display device having spacers with a more uniform height in both the pixel and peripheral regions of a reflective LCD device. Other and further objects and advantages will appear hereinafter.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a liquid crystal display (LCD) device having a more uniform spacer structure.
In accordance with one aspect of the invention, an LCD device is provided having a pixel region and a peripheral region adjacent to the pixel region, comprising a silicon substrate, an insulating layer on the substrate, a first metal layer above the insulating layer including an array of pixel electrodes in the pixel region and a peripheral portion in the peripheral region having a plurality of openings therein, a plurality of spacers in the openings, a second metal layer between the first metal layer and the substrate, and a plurality of walls each corresponding to one of the plurality of openings and extending substantially between the second metal layer and the first metal layer.
REFERENCES:
patent: 4682858 (1987-07-01), Kanbe et al.
Albu Lucian R.
Hausser Stefan
Janssen Peter J.
Kraft Karl-Heinz
Melnik George A.
Koninklijke Philips Electronics , N.V.
Ton Toan
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