Liquid crystal cells – elements and systems – Particular structure – Particular illumination
Reexamination Certificate
1999-01-08
2001-03-20
Dudek, James A. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Particular illumination
C349S058000, C349S065000
Reexamination Certificate
active
06204898
ABSTRACT:
1. Technical Field
The present invention relates to a liquid crystal display device which displays visible information, such as numbers or characters, using liquid crystal filled between a pair of substrates. The present invention also relates to an electronic device employing such a liquid crystal display device as a visible image display portion.
2. Discussion
In recent years, liquid crystal display devices have been widely used as a visible image display portion of various electronic devices, such as portable telephones and portable information terminals. A known type of conventional liquid crystal device comprises a liquid crystal structure consisting of a pair of substrates with liquid crystal filled therebetween, and an illuminator for illuminating the liquid crystal structure with light. Another known type of conventional liquid crystal device is the so-called transreflective liquid crystal display device which is capable of reflecting and transmitting light.
The transreflective liquid crystal display device comprises a semitransmissive type light reflecting plate at the back side of the aforementioned liquid crystal structure and an illuminator, which are disposed successively. When the transreflector liquid crystal display device is used in places which get a lot of outside light, such as outdoors, it is used as a reflective liquid crystal display device, since the illuminator is not used. When the transreflective liquid crystal display device is used in places which get only a small amount of outside light, it is used as a transmissive liquid crystal display device, since the illuminator device is used and turned on. Such a transreflector liquid crystal display device is disclosed in, for example, Japanese Unexamined Patent Publication No. 57-049271.
Compared to the so-called reflective liquid crystal display device which displays information by disposing only a light reflecting plate at the back side of the liquid crystal structure and using only outside light, the transreflective liquid crystal display device has the problem that the display becomes dark when information is displayed by reflection. This is because in such a transflective liquid crystal display device light transmission is achieved by making the reflective layer, such as an Al (aluminum) layer, of the light reflecting plate thin, or forming an opening, for allowing light transmission, in the reflecting layer, so that the brightness of the display obtained by reflection is sacrificed.
In addition, since in the conventional transreflector liquid crystal display device the illuminator that is disposed at the back side of the liquid crystal structure illuminates the liquid crystal structure through a semitransmissive reflecting plate, a very bright light source is required to illuminate the liquid crystal structure brightly, resulting in large electrical power consumption.
To overcome this problem, the applicant, in Japanese Unexamined Patent Publication No. 6-324331, has disclosed a so-called front light type liquid crystal display device that has an illuminator disposed at the observer side of the liquid crystal structure. For example, as shown in
FIG. 14
, the front light type liquid crystal display device includes an illuminator
7
disposed at the observer side (the top side in
FIG. 14
) of the liquid crystal structure
6
consisting of a pair of substrates with liquid crystal filled therebetween; and a light reflecting plate
8
that is disposed at the side opposite to the observer side of the liquid crystal structure
6
. The illuminator
7
includes, for example, a light source
2
, a transmissive light-guiding member
3
with protrusions
4
a
, and a side face reflecting plate
10
. As shown in
FIG. 13
, the protrusions
4
a
are disposed in a regular or irregular dot arrangement on a surface of the light-guiding member
3
.
This liquid crystal display device is used as a reflective liquid crystal display device when it is used in places which get a lot of outside light, such as outdoors, and as a transmissive liquid crystal display device when it is used in places which get only a small amount of outside light. In the former case, information is displayed by transmission of outside light through the transmissive light-guiding member
3
, and in the latter case, information is displayed by using illuminating light of the light source
2
. When the liquid crystal display device is used as a reflective liquid crystal display device, light beams from the light source
2
take the paths indicated by S
1
and S
2
of
FIG. 14
, so that they propagate through the light-guiding member
3
as they undergo total reflection, and arrive at side faces of corresponding protrusions
4
a
, after which they leave the light-guiding member
3
and illuminate the liquid crystal structure
6
. When such a front light type illuminator
7
is used, a semitransmissive light reflecting plate is not required, thereby allowing a bright display to be provided by light reflection.
However, the conventional liquid crystal display device of
FIG. 14
allows dust to easily enter between the liquid crystal structure
6
and the light-guiding member
7
. When dust enters between them, light from the light source
2
that has been turned on is scattered around the dust, causing the dust to become visible to the observer.
In the conventional liquid crystal display device, the surfaces of the liquid crystal structure
6
and the light-guiding member
3
are in direct contact with each other. In this case, there are particularly no problems if the distances between portions of the liquid crystal structure
6
and portions of the light-guiding member
3
are equal throughout the entire region of surface contact. However, when distances vary, interference patterns or the so-called newton rings are produced, making the visible image displayed on the liquid crystal display device difficult to see.
In view of the above-described problems, it is an object of the present invention to make it possible to prevent the quality of a visible image to be displayed from being reduced as a result of entry of dust into the liquid crystal display device and as a result of non-uniform close contact between the light-guiding member and another member of the liquid crystal display device.
SUMMARY OF THE INVENTION
To these ends, according to the present invention, the liquid crystal device may have the following structures.
(1) A first liquid crystal display device of the present invention comprises a liquid crystal structure having liquid crystal filled between a pair of substrates, a light source which emits light, and a light-guiding member, disposed at the observer side of the liquid crystal structure, for guiding the light from the light source to the liquid crystal structure, wherein a spacer member is disposed between the light-guiding member and the liquid crystal structure at the peripheral portions of the light-guiding member and the liquid crystal structure so as to be in close contact with the light-guiding member and the liquid crystal structure.
In the liquid crystal display device having the above-described structure, light from the light source strikes a light-guiding member and propagates therethrough, after which it leaves the light-guiding member and illuminates a liquid crystal structure. By controlling the voltage applied to a pair of electrodes in the liquid crystal structure, the light transmission state of the light is varied, so that a visible image, such as a number or a character, is displayed as a result of contrast, resulting from varying the light transmission state.
In addition, in the liquid crystal display device, a spacer member is disposed between the light-guiding member and the liquid crystal structure at the peripheral portions thereof so as to be in close contact therewith, so that dust no longer enters between the light-guiding member and the liquid crystal structure, as a result of which the quality of a visible image to be displayed on the liquid crystal display device can be maintained at a high level over
Dudek James A.
Harness & Dickey & Pierce P.L.C.
Seiko Epson Corportion
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