Illumination – Revolving
Reexamination Certificate
2001-01-26
2002-09-03
O'Shea, Sandra (Department: 2875)
Illumination
Revolving
C362S551000, C362S223000, C362S561000
Reexamination Certificate
active
06443584
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spread illuminating apparatus used as an illuminating means for signboards, various kinds of reflection-type display devices and the like, and more particularly, to a spread illuminating apparatus used as an illuminating means for a reflection-type liquid crystal display device.
2. Description of the Related Art
A liquid crystal display apparatus, which is characterized by being thin, small in occupied volume and lightweight, is used for many kinds of electric appliances such as a portable telephone, a personal computer or the like. Since a liquid crystal of the liquid crystal display device does not emit light by itself, when the liquid crystal display device is used in a dark place where sunlight or room light is not sufficiently available, a separate illuminating apparatus for lighting the liquid crystal is required besides the liquid crystal display device. Accordingly, it is desirable that such an illuminating apparatus is also small in size and low in power consumption. In order to attain this, light from the illuminating apparatus must be efficiently used. A conventional spread illuminating apparatus to answer such a demand is shown in
FIG. 10
as an example.
As shown in the figure, a spread illuminating apparatus
1
′ generally comprises a transparent substrate
2
formed of a light-transmissible material and a light source
5
disposed close to an end surface
8
of the transparent substrate
2
. The spread illuminating apparatus
1
′ makes light beams emitted from the light source
5
enter the transparent substrate
2
to light a liquid crystal display device (not shown in the figure) disposed under the transparent substrate
2
.
The light source
5
comprises a long plate-like light conductive member
3
formed of a transparent material and a spot-like light source (for example, light emitting diode)
4
disposed at an end of the light conductive member
3
and mounted on a flexible printed circuit board
6
. The light conductive member
3
is formed in a so-called wedge-shape, in which its thickness gradually decreases as it gets away from the spot-like light source
4
. Further, the light conductive member
3
is provided with an optical path conversion means
12
. The optical path conversion means
12
is formed on a surface opposite to a surface
9
facing the end surface
8
of the transparent substrate
2
, and comprises grooves
10
triangular in section and plane portions
11
adjacent to the grooves
10
. Light beams emitted from the spot-like light source
4
disposed at the end of the light conductive member
3
are adapted to enter substantially uniformly the end surface
8
of the transparent substrate
2
thanks to the wedge-shaped light conductive member
3
and the optical path conversion means
12
. Note that the light conductive member
3
is disposed at a predetermined distance from the end surface
8
of the transparent substrate
2
in such a manner that the surface
9
of the light conductive member
3
is aligned to the end surface
8
of the transparent substrate
2
.
A frame
13
is provided around the light conductive member
3
so that the light beams emitted from the spot-like light source
4
can enter efficiently the transparent substrate
2
. The frame
13
is formed substantially in C-shape and covers longitudinal surfaces of the light conductive member
3
except the surface
9
facing the transparent substrate
2
. The frame
13
is disposed in such a manner that a part of an upper plate inner surface
14
and a part of a lower plate inner surface
15
of the frame
13
overlap a part of the transparent substrate
2
at the end surface
8
side (see FIG.
12
). A hard plastic to which a film evaporated with metal such as silver, a white-color film or the like is attached, or a bent metal plate such as an aluminum plate or a stainless plate is pasted on the sides of the frame
13
that face the light conductive member
3
(inner surfaces).
The transparent substrate
2
is formed in a so-called wedge-shape, in which its thickness gradually decreases as it gets away far from the end surface
8
. Further, a light reflection pattern
19
is formed on an upper surface
16
of the transparent substrate
2
. The light reflection pattern
19
comprises grooves
17
triangular in section and plane portions
18
adjacent to the grooves
17
. Then, light beams coming from the light conductive member
3
are reflected uniformly on the whole surface of the transparent substrate
2
irrespective of the distance from the light conductive member
3
and illuminate the liquid crystal display device (not shown) disposed under the transparent substrate
2
.
Moreover, a reflection preventive film
20
is attached to a lower surface of the transparent substrate
2
. Even when light from the light source
5
is not used, that is, sunlight, room light or the like is used, the light does not cause diffused reflection inside the transparent substrate
2
because of the reflection preventive film
20
, and illuminates the liquid crystal display device disposed under the transparent substrate
2
. Thus, good images can be displayed on a liquid crystal screen.
By the way, in the spread illuminating apparatus
1
′ structured as described above, it is desirable that the areas of the opposing surfaces of the transparent substrate
2
and the light conductive member
3
are set equal to each other in order that the light beams emitted from the spot-like light source
4
are most efficiently transmitted into the transparent substrate
2
. In other words, when the dimension of the end surface (incident surface)
8
of the transparent substrate
2
and the dimension of the surface (exit surface)
9
of the light conductive member
3
that faces the incident surface
8
are equal to each other, the light beams can be most efficiently transmitted from the exit surface
9
to the incident surface
8
. However, because the reflection preventive film
20
is attached to the lower surface of the transparent substrate
2
, when the dimension of the incident surface
8
and the dimension of the exit surface
9
are set equal to each other, the thickness of the transparent substrate
2
turns out to be larger than the thickness of the light conductive member
3
by the thickness t of the reflection preventive film
20
(see FIG.
11
). In this state, if the light conductive member
3
and the transparent substrate
2
are simply set in the frame
13
, the exit surface
9
shifts off (slides down) relative to the incident surface
8
by the thickness t of the reflection preventive film
20
as shown in FIG.
12
. Therefore, it does not happen that light beams emitted from the exit surface
9
enter most efficiently the incident surface
8
, and a part of the light beams emitted from the exit surface
9
enters the reflection preventive film
20
. If the light beams enter the reflection preventive film
20
, the end portion of the reflection preventive film
20
is reflected in the liquid crystal screen thereby generating an unevenness in brightness. Accordingly, in order to transmit light in the most efficient manner, the exit surface
9
and the incident surface
8
must face each other in an accurately matching position.
SUMMARY OF THE PRESENT INVENTION
The present invention has been made in view of the above, and an object of the present invention is therefore to provide a spread illuminating apparatus in which a light source (light conductive member) can be positioned accurately and easily in the thickness direction relative to a transparent substrate thereby presenting a good liquid crystal display.
In order to solve the above problem, according to a first aspect of the present invention, there is provided a spread illuminating apparatus comprising a bar-like light source disposed close to an end surface of a transparent substrate formed of a light-transmissible material, characterized in that a frame is provided in such a manner as to cover the bar-like light sourc
Suzuki Shingo
Toyoda Koichi
DelGizzi Ronald E.
Minebea Co. Ltd.
O'Shea Sandra
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