Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2000-09-27
2003-10-07
Parker, Kenneth (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S044000
Reexamination Certificate
active
06630972
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a transmission liquid crystal panel through which rays of light are transmitted downwardly from above, and more particularly to a transmission liquid crystal panel in which encapsulated liquid crystal is driven by thin film transistors in an active matrix mode.
2. Description of the Related Art
Conventionally, image displays for displaying images on a screen utilizing liquid crystal have been put to practical use as liquid crystal projectors and projection televisions. Such an image display generally includes a light source, a transmission liquid crystal panel and a screen, in which rays of light emitted from the light source is transmitted through the transmission liquid crystal panel and radiated on the screen.
FIG. 1
shows a liquid crystal light valve
100
which is a prior art of the transmission liquid crystal panel. Liquid crystal light valve
100
comprises as its main components, transparent substrate
101
, numerous lower light blocking films
102
, numerous TFTs (Thin Film Transistor)
103
, a plurality of gate electrodes (not shown), a plurality of drain electrodes (not shown), a plurality of data electrodes
104
, a plurality of upper metal films
105
, planarizied layer
106
, numerous separate electrodes
107
, encapsulated liquid crystal
108
, common electrodes
109
, and opposite substrate
110
.
For the sake of simplicity, in the following description “lower side, upper side” will designate the circuit side, the liquid crystal side, respectively in the laminating direction of the various types of the layers in liquid crystal light valve
100
, as shown in FIG.
1
.
Transparent substrate
101
is made of a colorless and transparent insulating glass substrate, on the surface of which, a plurality of lower light blocking films
102
are laminated. Lower light blocking films
102
are made of WSi (tungsten silicide) with high heat resistance and low light transmittance, and are formed in a layer thickness and a pattern so as to shield each of numerous TFTs
103
from stray light in an upwardly slanted direction from below.
TFT
103
is located above lower light blocking film
102
through interlayer insulating film
111
, and includes a source region and a drain region formed thereon (not shown). The source region is connected to data electrode
104
, while the drain region is connected to the drain electrode (not shown). The gate electrode (not shown) of TFT
103
comprises a metal layer with a pattern extending in a lateral direction in the drawing, and is located generally on the upper surface of TFT
103
.
Data electrode
104
comprises an aluminum layer with a pattern extending in a direction normal to the drawing, and laminated above TFT
103
through interlayer insulating film
112
. In other words, the gate electrodes and data electrodes
104
form a matrix electrode, at the intersections of which respective TFTs
103
are arranged.
Upper metal film
105
is made of a highly reflective aluminum layer laminated above data electrode
104
through interlayer insulating film
113
, and is formed in such a layer thickness and a pattern as to shield data electrode
104
. Planarizied layer
106
is made of insulating organic resin such as polyimide and laminated on upper metal film
105
with its upper surface being formed flat.
Each separate electrodes
107
is made of ITO (Indium Tin Oxide) layer formed on the upper surface of planarizied layer
106
, and is connected to the drain electrode of TFT
103
.
More specifically, as mentioned above, the gate electrodes and data electrodes
104
form the matrix electrode which is separated into numerous rectangular sections aligned in the longitudinal and transverse directions, each section corresponding to each a display pixel in a dot matrix. Each separate electrode
107
is formed for each display pixel and connected to each TFT
103
through a contact hole (not shown).
Opposite substrate
110
is also made of a colorless and transparent insulating glass substrate and is laminated above planarizied layer
106
with a predetermined gap there between through a spacer member (not shown). Common electrodes
109
are also made of an ITO layer, and are uniformly distributed on the lower surface of opposite substrate
110
. Encapsulated liquid crystal
108
is made of liquid crystal encapsulated in the gap between planarizied layer
106
and opposite substrate
110
, and an electric field is applied to encapsulated liquid crystal
108
with separate electrode
107
and common electrodes
109
.
A peripheral circuit (not shown) is formed on the periphery of liquid crystal light valve
100
having the aforementioned laminated structure. The peripheral circuit is connected to TFTs
103
with the gate electrodes and data electrodes
104
in a matrix form. In addition, lower light blocking film
102
is grounded, and upper metal film
105
is also used as the wiring for the peripheral circuit.
Liquid crystal light valve
100
of the above configuration is utilized as part of an image display (not shown) together with a light source and a screen. In such an image display, the screen is laminated in an optical path from the light source through liquid crystal light valve
100
, and rays of light emitted from the light source is irradiated on liquid crystal light valve
100
from above.
When the image display inputs image data to the peripheral circuit of liquid crystal light valve
100
at this time, the peripheral circuit outputs driving signals corresponding to the image data to TFTs
103
through the gate electrodes and data electrodes
104
. TFTs
103
arranged in a matrix are individually turned with a driving voltage being then applied only to separate electrodes
107
connected to TFTs
103
turned ON.
Thus, the presence or absence of the light transmittance of encapsulated liquid crystal
108
is controlled in accordance with a dot matrix image. Rays of light transmit through liquid crystal light valve
100
from upward to downward and is irradiated on the screen, so that the dot matrix image is displayed on the screen.
In liquid crystal light valve
100
since encapsulated liquid crystal
108
is driven with TFTs
103
in the active matrix mode, the image display using liquid crystal light valve
100
can display a dot matrix image with high definition without causing crosstalk.
In the aforementioned liquid crystal light valve
100
, upper metal film
105
since data electrode
104
is shielded by electromagnetic noise, which causes can also be prevented the malfunction of TFT
103
, from entering data electrode
104
. In addition, upper metal film
105
is also utilized as the wiring of the peripheral circuit, which need not be newly formed.
When rays of light are incident on TFT
103
, includes an LDD (Lightly Doped Drain-Source) region (not shown) made of polysilicon, then leak current is generated to inhibit operational characteristics. Since the rays of light are transmitted through liquid crystal light valve
100
from above to downward, upper metal film
105
also serves to block the rays of light incident on TFT
103
from above.
In liquid crystal light valve
100
in which various types of layers are laminated, the rays of light transmitted from upward to downward may be reflected inside, and become stray light. However, lower light blocking film
102
formed below TFT
103
can prevent stray light reflected by the lower surface of transparent substrate
101
and directed toward a slant and upward direction from being entering directly on TFT
103
.
However, since upper metal film
105
serving as the wiring of the peripheral circuit and as a shield for data electrode
104
is made of an aluminum film and fine gaps exist on the boundaries among particles although upper metal film
105
effectively reflects incident ray of light in reality, it is difficult to effectively block the transmission of the rays of light.
For this reason, as shown in
FIG. 1
, the rays of light may enter TFT
103
after they pass through upper metal
Chung David
NEC Corporation
Parker Kenneth
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