Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2001-06-11
2003-06-10
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S068000
Reexamination Certificate
active
06577361
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a liquid crystal display device having a liquid crystal display panel composed of a liquid crystal cell which seals a liquid crystal layer between a pair of transparent substrates giving optical change to incident light by applying voltage to the liquid crystal layer and polarizers provided in a visible side of the liquid crystal cell and the opposite side thereof respectively, and an auxiliary light source provided in an opposite side with respect to the visible side. Namely, it relates to a transmissive liquid crystal display device and a transflective liquid crystal display device.
BACKGROUND TECHNOLOGY
Currently, among the liquid crystal display devices, there exist a transmissive liquid crystal display device which performs a display by lighting at an auxiliary light source provided therein all times, a reflective liquid crystal display device which performs a display utilizing light from an external light source (sunlight or illumination light source), and a transflective liquid crystal display device which performs a display utilizing reflecting light obtained from the external light source when the external light is bright, and performs the display utilizing transmission light obtained from a lighted inner auxiliary light source when the external light is dark.
The reflective liquid crystal display device is most effective to make the best use of the merit of low power consumption and thinness of a liquid crystal display device. However, since it can not perform display when external surroundings are dark, a transflective liquid crystal display device is widely used, which can perform display even if the external surroundings are dark by providing an auxiliary light source inside thereof.
An example of structure and function of a conventional transflective liquid crystal display device will be explained with FIG.
17
and FIG.
18
.
FIG. 17
is a plan view of a conventional transflective liquid crystal display device, and
FIG. 18
is a schematic enlarged sectional view taken along the line
18
—
18
in FIG.
17
. In
FIG. 17
, since most constituting members are transparent and a lower side member among members overlapping vertically, each other can be seen through, such a lower side member is also shown with solid lines. In the following explanation, a visible side which can be recognized by observers is taken as an upper side
In the above transflective liquid crystal display device, a liquid crystal cell (optical adjuster)
1
is composed such that a first substrate
2
and a second substrate
5
both made of a transparent material such as glass are opposedly disposed with a predetermined space and coupled to each other with a sealing member
16
to seal a liquid crystal layer
15
in-between thereof so that an optical change can be given to incident light by applying voltage on the liquid crystal layer
15
.
The transflective liquid crystal display device comprises a first polarizer (polarized light separator)
21
provided on the outside (the upper side in
FIG. 18
) of the first substrate
2
which is in the visible side of the liquid crystal cell
1
, and a second polarizer (polarized light separator)
22
provided on the outside (the lower side in
FIG. 18
) of the second substrate
5
which is on the opposite side with respect to the visible side, respectively, and an auxiliary light source
31
is provided on the opposite side of the second polarizer
22
with respect to the liquid crystal cell
1
.
Further explaining the liquid crystal cell
1
in detail, as shown in
FIG. 17
, on the inner surface of the first substrate
2
, stripe-shaped signal electrodes
3
made of an indium tin oxide (ITO) film which is a transparent conductive film are formed in a lateral direction with a predetermined space.
On the inner surface of the second substrate
5
, a color filter
9
composed of red (R) color filters
6
, green (G) color filters
7
and blue (B) color filters (not shown) is provided first, and a protective insulating film
10
is disposed thereon, then stripe-shaped scanning electrodes
11
made of ITO film are formed in a longitudinal direction with a predetermined space on the protective insulating film
10
, as shown in FIG.
17
.
The color filter
9
is formed in a state that the adjacent color filters having a color different from each other are overlapped slightly or abutted on each other. The protective insulating film
10
is provided to flatten the difference in level of the color filter
9
and to prevent deterioration of the signal electrodes
3
caused during the pattern forming process.
As shown in
FIG. 17
, an intersection point of the signal electrode
3
and the scanning electrode
11
intersecting to each other at right angles serves as a pixel portion
14
, and a display region is formed with a number of the pixel portions
14
provided in a matrix.
Alignment layers (not shown) as treatment layers to align the liquid crystal layer
15
in a predetermined direction are provided respectively on the opposing surfaces of the first substrate
2
and the second substrate
5
.
The first substrate
2
and the second substrate
5
are coupled with a fixed space therebetween with the sealing member
16
in a manner that the signal electrodes
3
on the first substrate
2
face the scanning electrodes
11
on the second substrate
5
, and the liquid crystal layer
15
is filled through the opening provided in the sealing member
16
, and then hermetically closed with a sealant
17
shown in FIG.
17
.
Though a twisted nematic (TN) liquid crystal, a super twisted nematic (STN) liquid crystal, or a homeotropic liquid crystal are used for the liquid crystal layer
15
, a twisted nematic (TN) liquid crystal having a twist angle of 90° is assumed to be used in this explanation.
A first polarizer
21
provided on the upper side of the first substrate
2
in the liquid crystal cell
1
is an absorption-type polarizer (absorptive polarized light separator) in which one polarization axis is a transmission axis and another polarization axis intersecting with the transmission axis at nearly right angles is an absorption axis, and a second polarizer
22
provided on the bottom side of the second substrate
5
is a reflection-type polarizer (reflective polarized light separator) in which one polarization axis is a transmission axis and another polarization axis intersecting with the transmission axis at nearly right angles is a reflection axis. The first polarizer
21
and the second polarizer
22
are disposed in such a manner that both transmission axes intersect with each other at right angles.
A scattering layer
4
made of a mixture of transparent resin and polyvinyl resin beads having different refractive indices is provided between the second polarizer
22
and the second substrate
5
, and a printed layer
23
made of translucent ink is further provided on the bottom surface of the second polarizer
22
.
According to a ratio of absorption to transmission of the printed layer
23
, brightness in a dark display state at the time of reflective display and in a bright display state at the time of transmissive display is determined.
The auxiliary light source
31
is disposed in further lower side of the second polarizer
22
, which is composed of a fluorescent tube
32
, a reflector
34
, a diffuser
33
and a prism sheet (not shown) in this example.
In the transflective liquid crystal display device thus structured, as shown in
FIG. 18
, when an external light from a main light source, for instance sunlight, passes through the first polarizer
21
and the first substrate
2
of the liquid crystal cell
1
, as a first incident light L
1
, and when made incident on a portion of the liquid crystal layer
15
in which no voltage is applied (background portion), the first incident light L
1
is made incident on a color filter
9
while being optically rotated or being given a phase difference by the liquid crystal layer
15
, passes through the second substrate
5
and the scattering layer
4
and comes to the se
Akiyama Takashi
Sekiguchi Kanetaka
Armstrong Westerman & Hattori, LLP.
Citizen Watch Co. Ltd.
Nguyen Hoan
Ton Toan
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