Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2000-05-16
2003-03-04
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S106000, C349S143000
Reexamination Certificate
active
06529255
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a liquid crystal display panel for a liquid crystal display device of the type used extensively in various apparatuses such as watches and hand-held calculators, particularly to a liquid crystal display panel that has color filters or a reflecting films or whose liquid crystal layer consists of a mixture of a liquid crystal and a polymer obtained by imparting a crosslinked structure to a monomer by ultraviolet light exposure.
2. Description of the Related Art
A liquid crystal display panel is constituted by disposing two glass panels or other transparent material substrates to oppose each other across a gap, providing one of the opposed substrate surfaces with multiple display electrodes and the other with multiple transparent counter electrodes to form a large number of pixel regions in matrix arrangement between the display electrodes and the counter electrodes, and filling a liquid crystal layer between the two substrates.
Images are displayed by selectively applying voltages between the display electrodes and the counter electrodes of the individual pixel regions so as to modify an optical characteristic of the intervening liquid crystal.
In the simplest structure of this type of liquid crystal display panel, the signal electrodes for inputting the display signal also serve as the display electrodes and a simple matrix of pixel regions is formed at the intersections between the signal electrodes and the counter electrodes. A multiplex drive system is adopted.
Most liquid crystal display panels in use today are of the active matrix type in which a display electrode is formed separately of the signal electrode at each picture element and a switching element is provided between each signal electrode and the associated display electrode.
Switching elements fall in two general categories, the three-terminal type using a thin film transistor (TFT) and the two-terminal type using a non-linear resistance element. A diode, varistor, thin film diode (TFD) or the like is used as the non-linear resistance element.
In addition, wide use is being made of color liquid crystal panels having color filters of three colors on one of the substrates and reflective liquid crystal display panels having a reflecting film on one of the substrates. Moreover, a liquid crystal display panel has been developed that uses a liquid crystal layer consisting of a mixture of a liquid crystal and a polymer obtained by crosslinking a monomer by exposure with ultraviolet light.
The liquid crystal display device using this type of liquid crystal display panel has the advantage of consuming much less power than other display devices.
While it is therefore used extensively as the display device of various kinds of equipment, particularly portable equipment, the display capacity of the liquid crystal display panel has increased steadily in recent years.
At the same time, demand for brighter displays has made it necessary to enhance the transmittance of the individual pixel regions and to increase the aperture ratio, i.e., the ratio of the pixel regions to the gaps between the pixel regions (non-display regions).
Although an attempt has also been made to increase display luminance by utilizing difference of refractive index in liquid crystal, this leads to change in hue depending on the positional relationship between the liquid crystal display panel and the observer and the relationship between the position of the pixel regions and the observer.
An example of the structure of a conventional color liquid crystal display panel using two-terminal type non-linear resistance elements will now be explained with reference to
FIGS. 29 and 30
.
FIG. 29
is an enlarged partial plan view of the liquid crystal display panel. For ease of illustration, some elements such as the second substrate, an insulated protection layer and an alignment film are omitted and lower members among members that overlap in the vertical direction are also indicated by solid lines in the plan views.
FIG. 30
is an enlarged sectional view taken along line A—A in FIG.
29
.
The first substrate
1
and the second substrate
6
shown in
FIG. 30
are transparent substrates such as glass panels. They are disposed opposite and parallel to each other.
A large number of signal electrodes
2
made of tantalum (Ta) film are formed on the first substrate
1
in the pattern of regularly spaced strips, as shown in FIG.
29
. Each signal electrode
2
is integrally formed at regular intervals along its longitudinal direction with laterally projecting first electrodes
2
a.
A non-linear resistance layer
3
made of tantalum oxide (Ta
2
O
5
), an anodic oxide film of the signal electrode
2
, is provided on each signal electrode
2
and its first electrodes
2
a.
Second electrodes
4
made of chromium (Cr) film are provided to overlap the non-linear resistance layer
3
, thereby constituting non-linear resistance elements
10
.
A large number of reflecting film display electrodes
15
made of aluminum (Al) are formed on the first substrate
1
in a closely spaced matrix arrangement. Portions of the second electrodes
4
make contact with the display electrodes
15
. As shown in
FIG. 29
, the first electrodes
2
a
and the display electrodes
15
are separated by a prescribed distance. Each display electrode
15
is disposed in alignment with a counter electrode
9
across an intervening liquid crystal layer
16
to constitute a pixel region
19
of the liquid crystal display panel.
On the other hand, as indicated by the oblique lines in
FIG. 29
, a two-layer black matrix
7
composed of a chromium oxide (CrO) film and a chromium (Cr) film is formed in a cross stripes pattern on the surface of the second substrate
6
opposed to the first substrate
1
. The black matrix
7
serves as a light-shielding film for preventing light leakage from the gaps between the display electrodes
15
formed on the first substrate
1
.
Color filters
11
,
12
and
13
that partially overlie the black matrix
7
are provided on the second substrate
6
at regions opposite the display electrodes
15
(regions completely covering the pixel regions
19
). These filters
11
,
12
and
13
are of three colors: blue (B), red (R) and green (G).
The counter electrodes
9
are further provided on the second substrate
6
as strips of indium-tin-oxide (ITO) film, which is transparent and conductive, running perpendicular to the signal electrodes
2
so as each to oppose one column of the display electrodes
15
. Data electrodes (not shown) are connected to the counter electrodes
9
for applying signals from an external circuit. Transparent and insulated protection layers
8
are provided between the counter electrodes
9
and the color filters
11
,
12
and
13
.
The opposed inner surfaces of the first substrate I and the second substrate
6
are provided with alignment films
21
A,
21
B as processed layers for regularly aligning the molecules of the liquid crystal.
A prescribed spacing is maintained between the first substrate
1
and the second substrate
6
by means of spacers
17
. The liquid crystal layer
16
is filled in the intervening gap. A polarization film
18
A is disposed on the outer (lower) surface of the first substrate
1
and a polarization film.
18
B is disposed on the outer (upper) surface of the second substrate
6
.
Since this liquid crystal display panel is not self-illuminating, it uses the external light
28
(natural or artificial light) from the side of the second substrate
6
for display.
Specifically, an optical characteristic of the liquid crystal in the regions between the display electrodes
15
and the counter electrodes
9
is modified via the non-linear resistance elements
10
by selectively applying driving voltages produced by an external circuit across the signal electrodes
2
and (via the data electrodes) the counter electrodes
9
. By this, display of a desired image can be effected by using the modification of the liquid crystal optical characteristic (incl
Armstrong Westerman & Hattori, LLP
Citizen Watch Co. Ltd.
Ton Toan
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