Liquid crystal cells – elements and systems – Particular structure – Particular illumination
Reexamination Certificate
2001-10-30
2004-02-17
Dudek, James (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Particular illumination
C362S035000
Reexamination Certificate
active
06693683
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photo-conductor plate and its manufacturing method, a surface emitting device and a liquid crystal display unit, and more particularly to the structure of a photo-conductor plate excelling in light transmittance when used as the front light of a liquid crystal display unit.
2. Description of the Prior Art
Usually, in a reflectance liquid crystal display unit using ambient light as the light source for displaying, its luminance is affected by the luminous energy of the ambient light, and therefore involves the problem that the visibility of the display extremely deteriorates in a dark place or any other environment where no sufficient ambient light is available.
Accordingly, in order to solve the above-noted problem, there is proposed a liquid crystal display unit of a type in which a front light (surface emitting device) is arranged on the front side of a reflectance liquid crystal display unit for use as an auxiliary light source. This front light-equipped liquid crystal display unit operates as a usual reflectance liquid crystal display unit in an environment where sufficient ambient light is available, such as outdoors in the daytime, and the front light is turned on as required to serve as a light source. A sectional structure of an example of such a liquid crystal display unit in which a front light is arranged on the front side of a liquid crystal display unit is shown in FIG.
8
. This liquid crystal display unit
200
shown in
FIG. 8
is configured of a liquid crystal display unit
220
and a front light
210
, and the front light
210
is arranged on the front face (top face in
FIG. 8
) of the liquid crystal display unit
220
so that a photo-conductor plate
212
is arranged in the display area of the liquid crystal display unit
220
.
The front light
210
is configured of a photo-conductor plate
212
formed by injection molding of transparent acrylic resin or the like and a light source
213
formed of a cold-cathode tube arranged on a side end face
212
a
of this photo-conductor plate
212
. The bottom face (the side toward the liquid crystal display unit
220
) of the photo-conductor plate
212
is used as a light emission face
212
b
from which light is emitted. The other face (the top face of the photo-conductor plate
212
) than this light emission face
212
b
is used as a reflection face
212
c
where a first slope
216
and a second slope
217
ensuing from it, formed at an inclination with respect to the light emission face
212
b,
are alternately and periodically arranged to alter the direction of light within the photo-conductor plate
212
. To the light emission face
212
b
of the photo-conductor plate
212
is stuck an anti-reflection film
215
.
The liquid crystal display unit
220
has a configuration in which a first substrate
221
and a second substrate
222
facing each other with a liquid crystal layer
223
pinched between them are integrated by joining with a sealing material
224
. On the side of the first substrate
221
toward the liquid crystal layer
223
are successively stacked a reflection layer
225
, containing a reflection film for reflecting light having come incident on the liquid crystal display unit
220
, and a display circuit
226
for driving and controlling the liquid crystal layer
223
, and a display circuit
227
is provided on the side of the second substrate
222
toward the liquid crystal layer
223
.
In the liquid crystal display unit
200
configured as described above, light emitted from the light source
213
is introduced into the photo-conductor plate
212
via the side end face
212
a
of the photo-conductor plate
212
, propagates within photo-conductor plate
212
and at the same time is reflected by the first slope
216
having a greater angle of inclination with respect to the direction of light introduction to undergo a change in its propagating direction toward the light emission face
212
b,
eventually to be emitted from the light emission face
212
b.
This light emitted from the light emission face
212
b
comes incident on the liquid crystal display unit
220
as illuminating light, passes the display circuits
226
and
227
and the liquid crystal layer
223
, is reflected by the reflection layer
225
, returns to outside the liquid crystal display unit
220
, and is transmitted by the light emission face
212
b
and the reflection face
212
c
of the photo-conductor plate
212
to reach the observer. In this way, the display on the liquid crystal display unit
220
is recognized by the observer.
However, the front light
210
of the liquid crystal display unit
200
configured as described above involves the problem that, as the anti-reflection film
215
is provided only on the light emission face
212
b
of the photo-conductor plate
212
, contrast is reduced by reflection from either the inside or the surface of the photo-conductor plate
212
. This is due to the reason explained below.
First, with the front light
210
described above, the light coming incident from outside on the reflection face
212
c
of the front light
210
is reflected by this reflection face
212
c
and directly reaches the observer to adversely affect his or her perception of the display.
Then, the light introduced from the light source
213
into the photo-conductor plate
212
via the side end face
212
a
of the photo-conductor plate
212
propagates within the photo-conductor plate
212
. At the same time, its propagating direction is turned toward the light emission face
212
b
by the first slopes
216
, steeper of the slopes
216
and
217
formed on the reflection face
212
c,
and about 96% of the light is emitted from the light emission face
212
b
to illuminate the reflectance liquid crystal display unit
220
. However, about 4% of it is reflected by the light emission face
212
b
to become reflected light directed to the reflection face
212
c
, passes the reflection face
212
c
and is emitted outside to reach the observer. Such reflected light reaches the observer without passing the liquid crystal display unit
220
, and therefore does not contribute to displaying. Therefore, this reflected light is perceived by the observer as noise, and contributes to the deterioration of contrast. Furthermore, as the reflected light is generated from the light reflected by the periodically formed first slopes
216
and passes the reflection face
212
c
on which the slopes
216
and
217
are periodically formed to reach the observer, it involves the risk of allowing moiré fringes to be generated by interference due to the periodicity of the slopes
216
and
217
.
Next, as described above, the light from the light source
213
, whose propagating direction is changed by the slopes
216
formed in succession periodically on the reflection face
212
c
of the photo-conductor plate
212
, is emitted from the light emission face
212
b
to illuminate the reflectance liquid crystal display unit
220
. The light coming incident on this liquid crystal display unit
220
is reflected by the reflection layer
225
of the liquid crystal display unit
220
toward the front light
210
, and again comes incident on the photo-conductor plate
212
. Part of the light traveling from this liquid crystal display unit
220
toward the front light
210
is reflected by the light emission face
212
b
and the reflection face
212
c
of the photo-conductor plate
212
to generate light which does not contribute to displaying but invites deterioration in contrast.
SUMMARY OF THE INVENTION
An object of the present invention, attempted in view of the above-described circumstances, is to provide a liquid crystal display unit equipped with a photo-conductor plate serving to enhance light transmittance by reducing reflection of light on its emission face and reflection face and a surface emitting device provided with this photo-conductor plate to be able to achieve efficient irradiation with light, and a liquid crystal display unit providing satisfac
Alps Electric Co. ,Ltd.
Dudek James
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