Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2001-09-17
2003-12-30
Kim, Robert H. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S114000
Reexamination Certificate
active
06671015
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to liquid crystal displays and, more particularly, to a technique suitable for use in a transflective liquid crystal display provided with a backlight and a reflection film.
2. Description of the Related Art
Substantially all mobile phones and mobile information terminals are now provided with liquid crystal displays, and recently, many such mobile electronic apparatuses have been provided with transflective liquid crystal displays.
In general, a transflective liquid crystal display includes a reflector provided on the interior or exterior of a pair of transparent substrates for reflecting incident light from outside and also includes a backlight at the back side thereof. The transflective liquid crystal display can be used as a reflective liquid crystal display and as a transmissive liquid crystal display by switching between a reflective mode in which solar light or an external illumination is used as a light source and a transmissive mode in which light from the backlight is used as a light source.
FIG. 5
is a partial sectional view of a conventional transflective liquid crystal display. In a conventional transflective liquid crystal display
100
shown in the drawing, a first substrate
110
and a second substrate
120
, which are composed of a transparent material, such as glass, are opposed to each other, and a liquid crystal layer
130
is enclosed therebetween.
An electrode layer
115
and an alignment film
116
are deposited in that order on a surface of the first substrate
110
facing the liquid crystal layer
130
. An electrode layer
125
and an alignment film
126
are deposited in that order on a surface of the second substrate
120
facing the liquid crystal layer
130
.
A polarizer
118
is provided on another surface of the first substrate
110
opposite to the liquid crystal layer
130
(i.e., the outer surface of the substrate
110
), and a reflector
119
having a reflection film
119
a
composed of a metal is provided on the outer surface thereof such that the reflection film
119
a
faces the polarizer
118
. A polarizer
128
is provided on the outer surface of the second substrate
120
. A backlight
105
for transmissive display is provided on the back of the liquid crystal display
100
.
The transflective liquid crystal display
100
having the structure described above is used, for example, as a display area of a mobile phone. When there is sufficient external light, the transflective liquid crystal display
100
operates in the reflective mode in which the backlight
105
is off, and in an environment where there is insufficient external light, it operates in the transmissive mode in which the backlight
105
is on.
However, in the transflective liquid crystal display
100
, since the reflector
119
is placed on the exterior of the substrate
110
, light entering the liquid crystal display
100
from outside must pass through two substrates,
110
and
120
, and two polarizers,
118
and
128
, before being reflected by the reflector
119
. Therefore, the propagation loss of light is increased, and it is not possible to obtain satisfactory brightness when the transflective liquid crystal display
100
is used as a reflective liquid crystal display.
On the other hand, in the transmissive mode in which the liquid crystal display
100
is used as a transmissive liquid crystal display, although the reflector
119
must transmit light from the backlight
105
, the thickness of the reflection film
119
a
is usually set at 1,000 to 1,500 Å in order to increase the reflectance of light. That is, pores are made in the reflection film
119
a
in order to transmit light.
However, in the method in which light from the backlight
105
is transmitted by providing the pores in the reflection film
119
a,
if the aperture ratio of the pores of the reflection film
119
a
is increased, the reflectance of the reflection film
119
a
is decreased, thereby decreasing brightness in the reflective mode. Therefore, it is not possible to sufficiently increase the aperture ratio, and satisfactorily bright display is not obtained when the backlight
105
is lit.
In order to solve the problems described above, a structure is disclosed, in which a reflector is placed between two substrates constituting a liquid crystal display so that the number of layers of substrates and polarizers through which light passes before reaching the reflector is decreased, and, by suppressing the propagation loss of light in the reflective mode, brighter reflective display can be obtained. By using such a structure, since display brightness in the reflective mode is ensured where possible, it is believed that brightness in the transmissive mode can be increased by decreasing the thickness of the reflection film for reflecting light to approximately 300 Å, but brightness in the reflective mode is slightly sacrificed.
However, even if such a structure is used, although the display brightness in the transmissive mode is improved, the brightness in the reflective mode is the same as that of the liquid crystal display
100
. If the thickness of the reflection film is increased to a certain degree by giving a high priority to the brightness in the reflective mode, the brightness in the transmissive mode becomes insufficient.
As described above, a transflective liquid crystal display in which satisfactorily bright, easily visible display is performed both in the reflective mode and in the transmissive mode has not yet been produced.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a transflective liquid crystal display in which a bright display is obtained by efficiently reflecting light in the reflective mode, and also in which bright display is obtained by satisfactorily transmitting light in the transmissive mode in which a backlight is lit. It is another object of the present invention to provide a transflector which is suitable for use in such a liquid crystal display.
In one aspect of the present invention, a liquid crystal display includes a pair of substrates which oppose each other with a liquid crystal layer therebetween, and a light source provided on the exterior of one of the substrates. At least an organic film, a metallic reflection film, an overcoat film, an electrode layer, and an alignment film are formed on the inner face of one of the substrates. Many concave portions are contiguously formed on a surface of the organic film, the inner surface of each concave portion constituting a part of a spherical surface, and the metallic reflection film has a thickness of 80 to 500 Å.
In the construction of the present invention described above, since many concave portions are contiguously formed on the surface of the organic film provided with the reflection film for reflecting light entering the liquid crystal display from outside, the inner surface of each concave portion constituting a part of a spherical surface, it is possible to greatly improve the reflection efficiency of light in comparison to the conventional transflective liquid crystal display. Therefore, it is possible to improve the transmittance of the liquid crystal display by decreasing the thickness of the metallic reflection film so that a bright display is also obtained for the transmissive liquid crystal display. Consequently, a bright display can be obtained both in the reflective mode and in the transmissive mode. Moreover, since bright display is enabled in the reflective mode, it is not necessary to turn on the backlight even when the liquid crystal display is used in a slightly dark environment. Consequently, power consumption can be reduced in an electronic apparatus provided with the liquid crystal display of the present invention.
In the liquid crystal display, preferably, the metallic reflection film has a thickness of 80 to 100 Å.
In such a construction, since the transmittance of the liquid crystal display can be improved by decreasing the thickness of the metallic reflectio
Kano Mitsuru
Ohizumi Mitsuo
Tanada Tetsushi
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Di Grazio Jeanne A.
Kim Robert H.
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