Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2002-07-23
2004-09-07
Chowdhury, Tarifur R. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S117000, C349S118000, C349S096000, C349S113000
Reexamination Certificate
active
06788371
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display device of external type in which a reflector is placed on the outer surface side of a liquid crystal panel.
2. Description of the Related Art
Regarding cellular phones and portable data terminals at present, liquid crystal display devices are mounted on almost all products. Recently, semitransparent reflective liquid crystal display devices have been mounted on most of these portable electronic devices.
The semitransparent reflective liquid crystal display device is provided with a reflection plate for reflecting light incident from an outside on the internal side or external side of a pair of transparent substrates constituting the liquid crystal display device, is further provided with a backlight on the back side thereof and, therefore, can be used while a reflective mode as a reflective liquid crystal display device using sunlight or an external illumination as a light source and a transmissive mode as a transmissive liquid crystal display device using light from the backlight as a light source are switched.
FIG. 19
is a diagram showing an example of the partial sectional structure of a conventional semitransparent reflective liquid crystal display device. This semitransparent reflective liquid crystal display device
50
includes a liquid crystal panel
50
a
having a configuration in which transparent electrode layers
53
and
54
are placed on respective counter-surface sides of a pair of glass substrates
51
and
52
, liquid crystal orientation films
55
and
56
are further placed on these transparent electrode layers
53
and
54
, respectively, and a liquid crystal layer
57
are placed between these orientation films
55
and
56
.
A first phase difference plate
66
and a first polarizing plate
68
are laminated on the external side of one glass substrate
51
in that order from the substrate
51
side. A second phase difference plate
67
and a second polarizing plate
69
are placed sequentially on the external side of the other glass substrate
52
, and a reflection plate
70
is attached on the external side of the second polarizing plate
69
with a transparent adhesive layer
70
a
therebetween.
In
FIG. 19
, reference numeral
65
denotes a sealing member for encapsulating the liquid crystal layer
57
between the glass substrates
51
and
52
, and reference numeral
75
denotes a backlight placed on the underside of the reflection plate.
As shown in FIG.
19
and
FIG. 20
, for example, a concave and convex surface is formed on the surface of a resin film
71
, a semitransparent reflection film
72
made of aluminum, etc., is further formed on this concave and convex surface using an evaporation method, etc., and, therefore, the reflection plate
70
is configured. The film thickness of this semitransparent reflection film
72
is specified to be within the range of 5 to 50 nm, and a part of light from the backlight
75
can be transmitted. This reflection plate
70
is attached while the surface on the semitransparent reflection film
72
side is faced toward the second polarizing plate
59
side.
The semitransparent reflective liquid crystal display device
50
having the aforementioned configuration is used as, for example, a display portion of a cellular phone. This semitransparent reflective liquid crystal display device
50
is operated in the reflective mode without lighting up of the backlight
75
when adequate external light is available and is operated in the transmissive mode with the backlight
75
being operated under circumstances where the external light is not available.
In the reflective mode, the light incident upon the first polarizing plate
68
is linearly polarized by this polarizing plate
68
, and the polarized light is elliptically polarized by passing through the first phase difference plate
66
, the liquid crystal layer
57
, and the second phase difference plate
67
. This elliptically polarized light is linearly polarized by passing through the second polarizing plate
69
. This linearly polarized light is reflected at the reflection plate
70
, is passed again through the second polarizing plate
69
, the second phase difference plate
67
, the liquid crystal layer
57
, and the first phase difference plate
66
, and is emitted from the first polarizing plate
68
.
In the transmissive mode, the light emitted from the backlight
75
and passed through the semitransparent reflection film
72
is linearly polarized by the second polarizing plate
69
, the polarized light is elliptically polarized by passing through the second phase difference plate
67
, the liquid crystal layer
57
, and the first phase difference plate
66
. This elliptically polarized light is linearly polarized by passing through the first polarizing plate
68
, and is emitted from the first polarizing plate
68
.
Meanwhile, as display performances of liquid crystal display devices, in general, it is required that (1) resolution, (2) contrast, (3) luminance of screen, (4) visibility, for example, viewing angle of wide range, and the like are excellent.
However, regarding the conventional semitransparent reflective liquid crystal display device
50
, since the second polarizing plate
69
has been placed between the reflection plate
70
and the liquid crystal panel
50
a
, in the reflective mode, problems arise as the incident light passes through the second polarizing plate
69
twice. These problems include the whole screen of the semitransparent reflective liquid crystal display device
50
becomes light green due to degradation of the spectral characteristic, contrast of the screen degrades and visibility is reduced.
Regarding the conventional semitransparent reflective liquid crystal display device
50
, since the reflection efficiency of the reflection plate
70
, on which the concave and convex surface has been formed, is reduced, the reflectance is reduced as a whole and, therefore, the need of the reflection plate for reflecting the incident light at a reflection angle of wider range is not adequately met. Consequently, regarding the semitransparent reflective liquid crystal display device
50
provided with the reflection plate
70
of this sort, problems arise in that the viewing angle is within the relatively narrow range of about 25 to 35 degrees and the luminance of the screen is not adequate.
Regarding the conventional semitransparent reflective liquid crystal display device
50
, since the phase difference plates and the polarizing plates is provided by two plates, respectively, the number of parameters of various optical characteristics is increased and, therefore, optimization of each parameter is complicated. Especially, in the transmissive mode, the increase in luminance and the improvement in contrast of the screen is difficult to achieve.
Consequently, it is considered that the second phase difference plate
67
and the second polarizing plate
69
are removed, the first phase difference plate
68
is made of a laminated plate of two layers exhibiting two different optical characteristics as the phase difference plate, only one plate of the first polarizing plate
68
placed on the first phase difference plate
66
is used as the polarizing plate and, therefore, the white display is lightened when the selection voltage is applied. However, in such a semitransparent reflective liquid crystal display device, since the change merely consists of reducing both of the phase difference plate and the polarizing plate by one plate, the reflection efficiency of the reflection plate
70
remains poor. This means that both the light display and the dark display (black display) are lightened and, therefore, the contrast is reduced.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the aforementioned circumstances. Accordingly, it is an object of the present invention to provide a liquid crystal display device in which no phase difference plate and no polarizing plate are placed between a liquid crysta
Kano Mitsuru
Ohizumi Mitsuo
Tanada Tetsushi
ALPS Electric Co. Ltd.
Brinks Hofer Gilson & Lione
Chowdhury Tarifur R.
LandOfFree
SEMITRANSPARENT REFLECTIVE LIQUID CRYSTAL DISPLAY DEVICE... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with SEMITRANSPARENT REFLECTIVE LIQUID CRYSTAL DISPLAY DEVICE..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and SEMITRANSPARENT REFLECTIVE LIQUID CRYSTAL DISPLAY DEVICE... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3221660