Illumination – Revolving
Reexamination Certificate
2001-08-31
2003-10-14
Quach-Lee, Y. My (Department: 2875)
Illumination
Revolving
C362S026000
Reexamination Certificate
active
06631998
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spread illuminating apparatus, and more particularly to a spread illuminating apparatus used as an illuminating means for a liquid crystal display device.
2. Description of the Related Art
A liquid crystal display device, which is low in profile, small in occupied volume, and lightweight, has been extensively used in electric products including portable telephones and notebook computers. However, since the liquid crystal display device does not emit light by itself, it is necessary to provide a separate illuminating apparatus besides the liquid crystal display device when used in dark places where the brightness of the sunlight and the illumination in room is not fully available. Thus, the illuminating apparatus to irradiate liquid crystals is desired to be compact in size and small in power consumption, and in recent years, a low profile spread illuminating apparatus of side light system (the light conductive plate system) is often used. The inventors of the present invention proposed a conventional spread illuminating apparatus disclosed in the Japanese Unexamined Patent Application Publication No. 2000-11723.
FIG. 7
shows an embodiment of the conventional spread illuminating apparatus.
As shown in the figure, a spread illuminating apparatus
1
′ generally comprises a transparent substrate
2
made of a light-transmissible material, and a light source
5
provided close to an end surface
8
of the transparent substrate
2
. Light emitted from the light source
5
is guided into the transparent substrate
2
to irradiate a liquid crystal display device (not shown in the figure) disposed on a lower side of the transparent substrate
2
.
The light source
5
comprises a light conductive member
3
made of a transparent material and shaped bar-like, and a spot-like light source (for example, a light-emitting diode)
4
disposed on one end of the light conductive member
3
. The light conductive member
3
is provided with an optical path conversion means
12
. This optical path conversion means
12
is formed with grooves, for example triangular in section, provided on a surface of the light conductive member
3
opposite to a surface
9
facing an end surface
8
of the transparent substrate
2
and thereby has a function to allow light emitted from the spot-like light source
4
to be made incident substantially uniformly on the end surface
8
of the transparent substrate
2
. The light conductive member
3
is disposed at a prescribed distance from the end surface
8
of the transparent substrate
2
with the surface
9
running parallel to the end surface
8
.
In order to efficiently introduce the light emitted from the spot-like light source
4
into the transparent substrate
2
, a light reflection member (frame)
13
is provided around the light conductive member
3
. The light reflection member
13
is substantially U-shaped and covers the longitudinal periphery of the light conductive member
3
except the surface
9
facing the transparent substrate
2
(refer to FIG.
8
). The light reflection member
13
may have a film on which a metal such as silver is vapor-deposited on its inner surface facing the light conductive member
3
, or may be formed of a hard resin with a white film adhered to its inner surface, or a bent metal sheet such as an aluminum sheet, a stainless sheet and the like.
FIG. 8
is a schematic side view showing a light reflection pattern
19
formed on an upper surface
16
of the transparent substrate
2
.
The light reflection pattern
19
comprises grooves
17
triangular in section and flat portions
18
adjacent thereto, which are formed at prescribed intervals therebetween in parallel to the light conductive member
3
. The grooves
17
are formed to vary in depth from each other so that light coming from the light conductive member
3
and entering the transparent substrate
2
may be reflected in a substantially uniform manner at the whole surface of the transparent substrate
2
irrespective of the distance from the light conductive member
3
(the light source
5
) to irradiate the liquid crystal display device (not shown in the figure) provided on the lower side of the transparent substrate
2
. In other words, the depth of the grooves
17
increases gradually in proportion to the increase in distance from the light conductive member
3
.
FIG. 9
shows another embodiment of a conventional spread illuminating apparatus.
As shown in the figure, a spread illuminating apparatus
1
″ comprises a plurality of light sources (
5
a
and
5
b
) to cope with a larger display screen or to improve the brightness of the screen. The light source
5
a
is disposed along one end surface
8
a
of the transparent substrate
2
, and the light source
5
b
is disposed along another end surface
8
b
opposite to the end surface
8
a
. Respective lights emitted from spot-like light sources
4
a
and
4
b
and entering light conductive members
3
a
and
3
b
are uniformly guided to the end surface
8
a
and the end surface
8
b
of the transparent substrate
2
by optical path conversion means
12
a
and
12
b
formed on one surface of the respective light conductive members
3
a
and
3
b
. In order to efficiently introduce the lights emitted from the spot-like light sources
4
a
and
4
b
into the transparent substrate
2
, light reflection members (frames)
13
a
and
13
b
are provided around the light conductive members
3
a
and
3
b
, respectively. The light reflection members
13
a
and
13
b
are substantially U-shaped and cover the longitudinal peripheries of the light conductive members
3
a
and
3
b
except surfaces
9
a
and
9
b
facing the transparent substrate
2
(refer to FIG.
10
).
FIG. 10
is a schematic side view showing a light reflection pattern
19
formed on an upper surface
16
of the transparent substrate
2
.
The light reflection pattern
19
comprises grooves
17
triangular in section and flat portions
18
adjacent thereto, which are formed at prescribed intervals therebetween in parallel to the light conductive members
3
a
and
3
b
. The grooves
17
are formed to vary in depth from each other so that lights coming from the light conductive members
3
a
and
3
b
and entering the transparent substrate
2
may be reflected in a substantially uniform manner at the whole surface of the transparent substrate
2
irrespective of the distance from the light conductive members
3
a
and
3
b
(the light sources
5
a
and
5
b
) to irradiate the liquid crystal display device (not shown in the figure) provided on the lower side of the transparent substrate
2
. In other words, the depth of the grooves
17
increases gradually in proportion to the increase in distance from the light conductive members
3
a
and
3
b
, and is largest at the center of the transparent substrate
2
.
Since, in the spread illuminating apparatus of the above-described construction, the grooves (prisms) formed on the surface of the transparent substrate have a triangular shape in section, there is the disadvantage of the undermentioned restrictions in ensuring the visibility of the liquid crystal display image and the workability of the light reflection pattern.
FIG. 3B
shows a path of light which is guided into the transparent substrate
2
and is reflected at the grooves
17
of the light reflection pattern
19
to irradiate the liquid crystal display device. When the groove interval L′ between two adjacent grooves
17
of the light reflection pattern
19
is large, the difference in brightness between a light area irradiated with light reflected at the grooves and a dark area not irradiated with the light reflected at the grooves becomes conspicuous, whereby a liquid crystal display device
10
cannot be irradiated uniformly. And when the groove interval L′ is set to be more than 0.3 mm, both the depth and width of the grooves
17
also increase to a certain degree, which causes the problem that the grooves
17
become visually recognizab
Egawa Motoji
Shimura Takahiro
Suzuki Shingo
Minebea Co. Ltd.
Quach-Lee Y. My
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