Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2000-02-29
2001-04-17
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S106000
Reexamination Certificate
active
06219120
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a reflective type liquid crystal display in which merging of colors caused by a parallax is not present, a high contrast can be attained, a superior displaying quality is provided and its stable driving can be realized.
2. Description of the Prior Art
In general, as a displaying form of a liquid crystal display, there are provided an opaque type display having a back-light, a transparent type display and a reflective type display. The reflective type liquid crystal display is a liquid crystal display in which only external light such as a solar light and an illumination light or the like is utilized to perform a displaying operation without applying any back-light, and the display of this type is frequently used in a thin portable type information terminal equipment in which a light weight and a low consumption power are required, for example.
FIG. 10
is a sectional view for showing a schematic configuration of the general prior art reflective type liquid crystal display, wherein this display is an example of an STN reflective type liquid crystal display of a simple matrix system, in particular.
This reflective type liquid crystal display has a schematic configuration in which a liquid crystal cell
72
for a reflective mode STN (Super-Twisted Nematic) system and a phase difference plate
73
are laminated on a lower deflector plate
70
of a reflector plate
71
with a lower deflector plate
70
, and a front deflector plate
74
is also laminated on this phase difference plate
73
.
The aforesaid liquid crystal cell
72
has a schematic configuration in which a lower glass substrate
75
, a color filter layer
76
, a lower transparent electrode layer
78
, a lower orientation film
79
, an upper orientation film
80
, an upper transparent electrode layer
81
and an upper glass substrate
82
spaced apart and oppositely arranged against the lower orientation film
79
are laminated in this order and an STN liquid crystal layer
83
is arranged between the aforesaid lower and upper orientation films
79
,
80
.
The aforesaid phase difference plate
73
is used for preventing a display from being colored in blue or yellow by accommodating a phase difference of light passing through the STN liquid crystal.
In the aforesaid prior art reflective type liquid crystal display, light incident to the front deflector plate
74
is linearly deflected by the deflector plate
74
and as the deflected light passes through the liquid crystal layer
83
, it is changed into an ellipse deflected light, wherein the deflected light is approached to a linear deflected light under application of the phase difference plate
73
and further the light is linearly deflected through the lower deflector plate
70
. The deflected light is reflected by the reflector plate
71
, passes through the liquid crystal layer
83
and is outputted from the front deflector plate
74
in the same manner as that of the incident light. A white display and a black display are changed over under an application of voltage and in the case that the white display is carried out, a direction of deflection before incident to the lower deflector plate
70
is coincided with a direction of a deflection axis of the lower deflector plate
70
, and in the case that the black display is carried out, they are crossed at a right angle.
However, in the prior art reflective type liquid crystal display shown in
FIG. 10
, although the display had some advantages that a consumption power can be reduced due to no requirement of a power supply for a back-light in addition to its thin-size and light weight features, it had a problem that its light display was slightly darkened as compared with that of the transparent type liquid crystal display having a back-light of high brightness.
In order to solve the aforesaid problems, there has been proposed that the lower deflector plate
70
arranged between the reflector plate
71
and the lower glass substrate
75
is removed and application of only one front deflector plate
74
arranged on the upper glass substrate
82
causes the light display to be bright at the time of selective application of voltage. However, in such a reflective type liquid crystal display as described above, since only one deflector plate is reduced, it may produce a problem that not only the light display is made bright, but also the dark display is made bright to cause their contrast to be decreased.
In view of the foregoing, the present applicant has shown, as a proposal in Japanese Patent Application No. Hei 9-36720, a reflective type liquid crystal display having a bright display in which a reflector, a color filter, a transparent electrode layer and an orientation film are arranged in sequence on the opposing surface of a lower glass substrate, a transparent electrode layer and an orientation film are arranged in sequence on the opposing surface of the aforesaid upper glass substrate, a first phase difference plate and a second phase difference plate are arranged in sequence on the outer surface of the upper glass substrate, a liquid crystal layer is arranged between the orientation films of the upper and lower glass substrates, and further a product &Dgr;nd of anisotropy of refractive index &Dgr;n of a liquid crystal and a layer thickness d of a liquid crystal, a relation between phase differences R
1
, R
2
of each of the first and second phase difference plates or an angle of a deflecting axis of the deflector plate or an angle of a lagging axis of the first and second phase difference plates are limited to a specified range. In addition, it is preferable to use a reflector member that, as the reflector member installed in such a reflection type liquid crystal display having the aforesaid configuration, some fine corrugated (concave or convex) portions are formed on the surface of the lower glass substrate in order to increase a visual angle, a metallic reflective film such as either an Al film or Ag film or the like is formed on the corrugated surface, thereby the surface of the metallic reflective film is provided with the corrugated surface acting as a reflective surface.
SUMMARY OF THE INVENTION
However, in the case of the liquid crystal display storing the reflector member having such corrugated surfaces, there occurred a problem that an irregular thickness is produced in a liquid crystal layer due to some corrugated states of the corrugated surface and a display quality is reduced. In addition, in the case of this liquid crystal display storing the reflector therein, an electrical insulating characteristic found between the reflector and the transparent electrode layer becomes a problem, an insufficient insulating characteristic does not enable a sufficient voltage to be applied to the liquid crystal layer when the liquid crystal display is driven, a certain influence appears in the display and a stable driving can not be attained.
The present invention has been invented in view of the aforesaid circumstances and it is an object of the present invention to provide a reflective type liquid crystal display in which an irregular thickness of the liquid crystal layer can be reduced and a sufficient insulating characteristic can be assured between the reflector and the transparent electrode layer (a display electrode).
In the present invention, the aforesaid problems are solved by applying a reflective type liquid crystal display comprised of a reflector member having corrugated surface stored therein, an overcoat layer formed on the aforesaid corrugated surface of the reflector member for making the aforesaid corrugated surface flat and a color filter layer formed on the overcoat layer characterized in that a thickness of the aforesaid overcoat layer is more than twice of a depth of the concave part in the corrugated surface of the aforesaid reflector member.
In accordance with the reflective type liquid crystal display of the present invention, the overcoat layer is formed on the corrugated surface of the stored reflector member,
Ishitaka Yoshihiko
Kano Mitsuru
Ohizumi Mitsuo
Omote Kenji
Sasaki Yorihiko
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Choudhury Tarifur R.
Sikes William L.
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