Illumination – Illuminated scale or dial – Edge illuminated modifier or light rod/pipe
Reexamination Certificate
2002-08-29
2004-05-11
O'Shea, Sandra (Department: 2875)
Illumination
Illuminated scale or dial
Edge illuminated modifier or light rod/pipe
C362S035000, C362S327000
Reexamination Certificate
active
06733148
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 (hereinafter referred to as “LCD”) which is low in profile, small in occupied volume, and lightweight has been extensively used in electric products including personal computers and cellular phones, and the demand therefor has been increasing. However, since a liquid crystal used for the LCD does not emit light by itself, it is necessary to provide a separate illuminating apparatus besides the LCD in order to irradiate a liquid crystal when the LCD is used in dark places where sunlight or room light is not fully available. Thus, the illuminating apparatus for irradiating the liquid crystal is desired to be compact and small in power consumption, and a low profile spread illuminating apparatus of side light type (light conductive plate type) is often used recently.
FIG. 4
is an exploded perspective view showing a conventional spread illuminating apparatus
1
′ of side light type in which a spot-like light source is mounted on a flexible printed circuit (hereinafter, referred to as “FPC”).
As shown in the figure, the spread illuminating apparatus
1
′ generally comprises a light conducive plate
2
made of a light-transmissible material, lamps
5
a
and
5
b
comprising light conductive bars
3
a
and
3
b
and spot-like light sources
4
a
and
4
b,
respectively, and arranged respectively along end surfaces
8
and
18
of the light conductive plate
2
, an FPC
6
on which the spot-like light sources
4
a
and
4
b
are mounted, and light reflection members (lamp frames)
13
a
and
13
b
covering the lamps
5
a
and
5
b.
Light rays emitted from the lamps
5
a
and
5
b
and introduced into the light conductive plate
2
are reflected therein so as to irradiate an LCD (not shown) disposed under the light conductive plate
2
.
The light conductive plate
2
has a light reflection pattern
29
on a top surface (observation-side surface)
25
thereof so as to uniformly spread the light rays introduced thereinto through the end surfaces
8
and
18
toward the LCD entirely through a bottom surface
26
. The light reflection pattern
29
comprises a plurality of grooves
27
and a plurality of flat portions
28
each present between adjacent grooves, and is oriented parallel to the length direction of the light conductive bars
3
a
and
3
b.
Alternatively, the light reflection pattern
29
may comprise only grooves continuously arrayed, and the grooves do not have to be parallel with the length direction of the light conductive bars
3
a
and
3
b
but may be oriented to have a predetermined angle thereto. With the light reflection pattern thus constructed, the light rays having entered the light conductive plate
2
are substantially uniformly reflected at the whole top surface of the light conductive plate
2
thereby uniformly irradiating the LCD disposed under the light conductive plate
2
.
As above described, the lamps
5
a
and
5
b
are composed of the light conductive bars
3
a
and
3
b
and the spot-like light sources
4
a
and
4
b
(for example, light-emitting diodes), respectively. The light conductive bars
3
a
and
3
b
have optical path conversion means
12
a
and
12
b,
respectively, formed on one side surface thereof opposite to a side surface facing the light conductive plate, and have the spot-like light sources
4
a
and
4
b,
respectively, disposed close to an end surface thereof. The spot-like light sources
4
a
and
4
b
are mounted by soldering at land portions formed on the FPC
6
. The land portions are electrically connected to a power source pattern (not shown) formed on the FPC
6
, and power is supplied to the land portions from a connect section
6
a
of the FPC
6
via the power source pattern.
The lamp frames
13
a
and
13
b
are provided so as to cover the lamps
5
a
and
5
b,
respectively, thereby allowing light rays emitted from the spot-like light sources
4
a
and
4
b
to efficiently enter the light conductive plate
2
, preventing the light conductive bars
3
a
and
3
b
from being damaged by contact with any other members, and making the light conductive bars
3
a
and
3
b
further dustproof. The lamp frames
13
a
and
13
b
are shaped substantially like U-letter, and cover respective longitudinal surfaces of the light conductive bars
3
a
and
3
b
except respective surfaces facing the light conductive plate
2
, and cover also both end portions of the light conductive plate
2
. The lamp frames
13
a
and
13
b
are each formed of a hard resin member, on inner surface of which a film with a metal such as silver vapor-deposited or a white film is adhered or formed of a bent metal sheet such as an aluminum sheet, a stainless steel sheet, or the like.
FIG. 5
is a schematic view showing how light rays emitted from a spot-like light source are guided into a light conductive plate.
The light rays radially emitted from the spot-like light source
4
are reflected and refracted at four side surfaces of the light conductive bar
3
substantially rectangular in section or by the lamp frame
13
covering the longitudinal surfaces of the light conductive bar
3
, and most of the light rays are guided to the light conductive plate. More specifically, as shown in the figure, some light elements
7
a
and
7
b
enter the light conductive bar
3
through the end surface thereof, and are confined therein due to a difference in the refractive index between the light conductive bar
3
and the atmosphere. Then, the light elements
7
a
and
7
b
are guided into the light conductive plate
2
after being reflected and refracted at grooves
14
of an optical path conversion means. But, some light elements such as an element
7
c
do not enter the light conductive bar
3
, and directly enter the light conductive plate
2
. This occurs if members are not appropriately assembled, specifically, if there is too much space between the spot-like light source
4
and the end surface of the light conductive bar
3
. When this occurs, a linear bright line appears on a screen.
Another factor for generating a bright line on the screen will be described with reference to FIG.
6
. In the figure, the members making up the spread illuminating apparatus are correctly and accurately positioned and assembled. In such a state, when the light conductive plate
2
is observed from a left-to-right direction (a direction parallel to the grooves
27
of the light reflection pattern
29
formed on the light conductive plate
2
), a zonal bright line indicated by a reference numeral
7
d,
so-called reflected bright line, appears on an end surface
15
of the light conductive bar
3
due to reflection at the grooves
27
and reflection at the bottom surface of the light conductive plate
2
(Fresnel reflection).
The spot-like light sources
4
a
and
4
b
need to be arranged right in font of and close to the end surfaces of the light conductive bars
3
a
and
3
b,
respectively, in order to allow light rays to efficiently enter the light conductive bars
3
a
and
3
b.
According to the prior art shown in
FIG. 4
, the spot-like light sources
4
a
and
4
b
are mounted on the FPC
6
as shown in FIG.
7
. Accordingly, when the spot-like light sources
4
a
and
4
b
are disposed close to respective end surfaces of the light conducive members
3
a
and
3
b,
parts of the FPC
6
(shaded area) are located under the end portions (bottom side) of the light conductive bars
3
a
and
3
b
as shown in FIG.
8
. In this case, since the FPC
6
has, for example, a yellow color, an orange color, or the like, when light rays radially emitted from the spot-like light sources
4
a
and
4
b
are partly reflected at the FPC
6
and enter the light conductive plate
2
, a bright line of the color of the FPC
6
appears on the screen due to the reflected light rays. T
Alavi Ali
Minebea Co. Ltd.
O'Shea Sandra
Oliff & Berridg,e PLC
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