Liquid crystal cells – elements and systems – Particular structure – Particular illumination
Reexamination Certificate
1999-03-25
2001-06-05
Dudek, James A. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Particular illumination
C349S012000
Reexamination Certificate
active
06243150
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a reflective liquid crystal display device having a tablet.
2. Description of the Related Art
FIGS. 7
,
8
, and
9
are a cross-sectional view, a principal-part sectional view, and an explanatory view, respectively, of a conventional liquid crystal display device. The conventional liquid crystal display device has a box-shaped casing
21
molded from synthetic resin which is open at the top thereof. The casing
21
is composed of a bottom plate
21
a
, and four side walls
21
b
formed on all sides of the bottom plate
21
a.
A reflective liquid crystal display element
22
includes a display portion
22
a
in which liquid crystal is sealed between two transparent glass substrates, and a back reflecting plate
22
b
disposed outside one of the substrates in the display portion
22
a
and having a light diffusing ability.
A control member
23
is electrically connected, in which electric parts, such as an IC, are mounted on the side of the liquid crystal display element
22
.
A tablet
24
is an input device for converting the coordinates of the position in the plane into electric signals, and comprises a lower substrate
24
a
made of a transparent glass or the like; a transparent lower electrode portion
24
b
disposed on the upper surface of the lower substrate
24
a
and made of indium oxide or the like; a plurality of dot spacers
24
c
arranged at intervals on the upper surface of the lower electrode portion
24
b
, which are formed by being printed in a transparent ink of acrylic resin or the like; a film
24
d
made of a transparent flexible synthetic resin and disposed above the dot spacers
24
c
; and a transparent upper electrode portion
24
e
made of indium oxide or the like, which is disposed on the lower surface of the film
24
d
to oppose the lower electrode portion
24
b.
The thickness of the lower substrate
24
a
is approximately 0.7 mm to 1.8 mm. The dot spacers
24
c
are formed in a substantially fixed size so that they are 5 &mgr;m to 20 &mgr;m in height and 50 &mgr;m to 100 &mgr;m in diameter. The dot spacers
24
c
are arranged at intervals of 1.5 mm to 2 mm, and serve to space the lower electrode portion
24
b
and the upper electrode portion
24
e
. The entire thickness of the tablet
24
is approximately 1 mm to 2 mm.
A light guide
25
is made of a transparent material of acrylic resin or the like, and includes a light guide member
25
a
having a thickness of approximately 2 mm, and a plurality of semicircular dot patterns
25
b
formed on one side of the light guide member
25
a
by being printed in a transparent ink of acrylic resin or the like. These dot patterns
25
b
are equally sized so that they are approximately 20 &mgr;m in height and 50 &mgr;m to 100 &mgr;m in diameter, and are spaced at equal intervals.
Inside the casing
21
, the liquid crystal display element
22
, to which the control member
23
is attached, is held with the side of the back reflecting plate
22
b
down. The light guide
25
is located at a distance of approximately 0.5 mm above the liquid crystal display element
22
with the side of the dot patterns
25
b
up. The tablet
24
is located at a distance of approximately 0.5 mm above the light guide
25
with the side of the film
24
d
up. A lamp
26
having a diameter of approximately 1.5 mm and shaped like an elongated rod is placed inside the casing
21
in an appropriate manner so that it is positioned at the end face of the light guide member
25
a.
A mounting member
27
formed of a metal plate is composed of a top plate
27
a
, an opening portion
27
b
formed in the top plate
27
a
, and four side plates
27
c
formed by bending all sides of the top plate
27
a
. The opening portion
27
b
is larger than that of an effective display region of the liquid crystal display element
22
. The mounting member
27
is fixed the casing
21
in an appropriate manner so that the plate
27
a
covers the control member
23
and the lamp
26
is held inside the casing
21
. Furthermore, the mounting member
27
is mounted so that the effective display region of the liquid crystal display element
22
can be visually recognized from the opening portion
27
b
via the tablet
24
. In this way, the conventional liquid crystal display device is constructed.
In the conventional liquid crystal display device thus constructed, for example, a user presses an input pen (not shown) or the like against the film
24
d
in the tablet
24
disposed above the liquid crystal display element
22
, in response to the contents displayed on the liquid crystal display element
22
, so as to deform the film
24
d
, thereby bringing the upper electrode portion
24
e
into contact with the lower electrode portion
24
b
and inputting desired coordinates as electric signals. The display on the liquid crystal display element
22
is appropriately changed according to the input electric signals.
When the conventional liquid crystal display device is used in a dark environment, light from the lamp
26
enters the inside of the light guide member
25
a
from the end face thereof. In this case, a part of the incident light that travels upward is irregularly reflected by the dot patterns
25
b
formed on the upper surface of the light guide member
25
a
to change the angle, and then travels downward, as shown by the arrow X in FIG.
9
. Since the light that is incident from the lamp
26
and travels toward the bottom of the light guide member
25
a
is incident on the lower surface of the light guide member
25
a
at a small angle, most components thereof are specularly reflected between the lower surface of the light guide member
25
a
and the atmosphere to travel upward, and are irregularly reflected by the dot patterns
25
b
to travel downward, as shown by the arrow Y in FIG.
9
. Of the light that is thus directed downward, light, which is incident on the lower surface of the light guide member
25
a
at a nearly perpendicular angle, is transmitted through the light guide member
25
a
, and is radiated onto the display portion
22
a
, and the back reflecting plate
22
b
disposed thereunder in the liquid crystal display element
22
. Therefore, the liquid crystal display device can be used in a dark environment. When the conventional liquid crystal display device is used in a light environment, since external light impinges on the back reflecting plate
22
b
, visibility of the liquid crystal display element
22
can be maintained without using the lamp
26
.
In the conventional liquid crystal display device, however, when the lamp
26
is provided, it is necessary to interpose the light guide
25
between the tablet
24
and the liquid crystal display element
22
. This increases the thickness and cost of the liquid crystal display device.
Furthermore, it is difficult for the lamp
26
to sufficiently illuminate the entire effective display region of the liquid crystal display element
22
. In particular, it is difficult for the light to reach the vicinity of an end face W of the light guide
25
opposite from the side of the lamp
26
. Moreover, since some light travels outside from the end face W, as shown by the arrow Z in
FIG. 9
, it is impossible to sufficiently illuminate the liquid crystal display element
22
.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a liquid crystal display device in which the entire effective display region of a liquid crystal display element can be sufficiently illuminated by a lamp, and to reduce the thickness of the liquid crystal display device.
In order to achieve the above object, according to an aspect of the present invention, there is provided a liquid crystal display device including a tablet having a transparent lower substrate and a transparent dot spacer, a liquid crystal display element disposed below the tablet, and a lamp positioned at an end face of the lower substrate, wherein a reflecting member is prov
Sasagawa Hideto
Watanabe Takeshi
Alps Electric Co. Ltd
Brinks Hofer Gilson & Lione
Dudek James A.
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