Liquid crystal cells – elements and systems – Particular structure – Particular illumination
Reexamination Certificate
2001-09-12
2004-06-08
Flynn, Nathan J. (Department: 2826)
Liquid crystal cells, elements and systems
Particular structure
Particular illumination
C349S061000, C349S062000, C349S063000, C349S067000, C349S070000, C349S113000, C349S117000, C349S114000, C349S119000
Reexamination Certificate
active
06747714
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a liquid crystal display, and more specifically, it relates to a transflective liquid crystal display which can achieve reflective mode display and the transmissive mode display in a switching manner, and an electronic apparatus incorporating the liquid crystal display.
2. Description of Related Art
Reflective liquid crystal displays that achieve display by making use of the external light cannot be viewed in a dark location. Thus, such a reflective liquid crystal display has been typically used as a transflective display having an auxiliary light source. Most reflective color liquid crystal displays which have quickly become popular in recent years are also used as transflective color liquid crystal displays as disclosed, for example, in the following published international application (International Application Number: WO99/40480).
A configuration of a conventional transflective liquid crystal display is described below with reference to FIG.
8
.
FIG. 8
shows a first polarizer
801
, a first retardation film
802
, a second retardation film
803
, a liquid crystal cell
804
, a third retardation film
805
, a second polarizer
806
, and a backlight
807
. The liquid crystal cell
804
includes a first substrate
811
and a second substrate
812
, a liquid crystal
813
, a scanning electrode
814
disposed on an inner surface of the first substrate
811
, and a transflector
815
which is also used as a signal electrode disposed on an inner surface of the second substrate
812
. The backlight
807
includes a light guide plate
821
and a reflector
822
, and a light source
823
.
Next, the operating principle of a conventional transflective liquid crystal display is described below with reference to FIG.
9
.
FIG. 9
shows a first polarizer
901
, a first retardation film
902
, a second retardation film
903
, a liquid crystal
904
, a transflector
905
, a third retardation film
906
, a second polarizer
907
, a light guide plate
908
, and a reflector
909
.
FIG. 9
also shows an ON area
911
of the liquid crystal
904
, and an OFF area
912
of the liquid crystal
904
. In the ON area
911
, the selective voltage is applied to the liquid crystal
904
, and the tilt angle, i.e., the angle formed between the liquid crystal molecule and the substrate surface, is increased. On the other hand, in the OFF area
912
, the non-selective voltage is applied to the liquid crystal
904
, and the tilt angle is decreased.
Firstly, the reflective mode display is described below. An external light
921
is converted into a linearly polarized wave by the first polarizer
901
, transmitted through the first retardation film
902
, the second retardation film
903
and the liquid crystal
904
, and then converted into the circularly polarized wave in the ON area
911
, or the linearly polarized wave in the OFF area
912
. Thereafter, the light is reflected by the transflector
905
, transmitted through the liquid crystal
904
, the second retardation film
903
, and the first retardation film
902
, and converted into the linearly polarized wave orthogonal to the incident polarized wave in the ON area
911
, absorbed by the polarizer
901
to form a black display
931
, or converted into the linearly polarized wave parallel to the incident polarized wave in the OFF area
912
, and transmitted through the polarizer
901
to form a white display
932
.
Next, the transmissive mode display is described below. The light emitted from a backlight light source
922
is diffused by frosting or the like (not shown in the figure) cut in the light guide plate
908
while repeating the total reflection in the light guide plate
908
, and emitted to the liquid crystal cell side. This light is converted into the linearly polarized wave by the second polarizer
907
, and further converted into the circularly polarized wave by the third retardation film
906
. Black can be displayed in the ON area
911
, and slightly dark white can be displayed in the OFF area
912
by setting this circularly polarized wave so that it is circularly polarized in the same rotational direction as the circularly polarized wave when the external light incident in the ON area
911
of the liquid crystal in the reflective mode display is reflected by the transflector
905
, for example, a clockwise circularly polarized wave. On the other hand, the circularly polarized wave reflected downward by the transflector
905
becomes counterclockwise circularly polarized, returned to the linearly polarized wave by the third retardation film
906
, and then, absorbed by the second polarizer
907
.
However, such a conventional transflective color liquid crystal display has a problem in that the transmissivity is low. As described above, this is attributable to the fact that the light of the backlight reflected by the transflector
905
is absorbed by the second polarizer
907
due to the conversion of the polarized wave by the third retardation film
906
. The transmissivity of the transflector
905
is only about 5 to 15%, and thus, 85 to 95% of the light is actually wasted.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a transflective liquid crystal display of high transmissivity by recycling the light reflected by the transflector to enhance the efficiency of utilization of the light by making use of a backlight having a diffusing polarizer.
A structure in accordance with the present invention to address the above problem is described below.
The liquid crystal display in accordance with the present invention includes a liquid crystal cell having a liquid crystal held between a pair of substrates, a transflector disposed inside the liquid crystal cell, a backlight disposed outside of the liquid crystal cell, and a retardation film disposed between the liquid crystal cell and the backlight. The backlight includes a light guide plate and a light source. A diffusing polarizer is disposed on one side of the light guide plate, and a reflector is disposed on the other side of the light guide plate. The diffusing polarizer is a polarizer having the function of diffusing a predetermined component of the linearly polarized wave, and allowing the other component of the polarized wave to be transmitted. The retardation film has the function of converting the linearly polarized wave incident therein into the substantially circularly polarized wave, and preferably includes at least one ¼ wavelength plate. The diffusing polarizer is preferably adhered to the light guide plate. In the above configuration, the linearly polarized wave is removed from the light guide plate by the diffusing polarizer, and converted into the circularly polarized wave by the retardation film and incident in the transflector. The light reflected by the transflector is also reflected by the reflector of the backlight, and recycled. Since no member that absorbs the light is present therebetween, most of the light of the backlight is transmitted through the transflector, which achieves a transmissive display that is brighter than a conventional transmissive display.
The liquid crystal display in accordance with the present invention further includes a retardation film that is disposed between the light guide plate of the backlight and the reflector. This retardation film also has the function of converting the linearly polarized wave incident therein into a substantially circularly polarized wave, and preferably includes at least one ¼ wavelength plate. In particular, in the above liquid crystal display, the reflector of the backlight preferably has a reflecting surface that is close to a mirror surface, and disturbs no polarized wave. In the above configuration, the light reflected by the transflector is returned to the same polarized state, and recycled, and thus a bright transmissive display with high contrast can be obtained.
An electronic apparatus in accordance with the present invention includes the liquid crystal display acc
Erdem Fazli
Flynn Nathan J.
Oliff & Berridg,e PLC
Seiko Epson Corporation
LandOfFree
Liquid crystal display device and electronic apparatus... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Liquid crystal display device and electronic apparatus..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Liquid crystal display device and electronic apparatus... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3360179