Illumination – Illuminated scale or dial – Edge illuminated modifier or light rod/pipe
Reexamination Certificate
2001-11-01
2003-05-13
O'Shea, Sandra (Department: 2875)
Illumination
Illuminated scale or dial
Edge illuminated modifier or light rod/pipe
C362S035000, C362S555000, C385S901000
Reexamination Certificate
active
06561661
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spread illuminating apparatus particularly used as an illuminating means for a liquid crystal display.
2. Description of the Related Art
A demand for a liquid crystal display has been increased mainly for personal computers and mobile phones since the liquid crystal display which operates at low power consumption features low profile and light weight. Since a liquid crystal which is a component member of the liquid crystal display does not emit light by itself unlike a light emitting element such as a cathode ray tube, an illuminating means for illuminating the liquid crystal for use in a dark place is required. In particular, in the recent demand for lower profile and smaller power consumption, there has been a growing tendency to employ a spread illuminating apparatus of side light type (light conductive member type) as an illuminating means for illuminating the liquid crystal display.
FIG. 5
illustrates a spread illuminating apparatus of side light type, particularly intended for increasing brightness. A spread illuminating apparatus
1
′ is generally composed of a transparent substrate
4
disposed so as to cover a surface
3
(an observation surface) of a liquid crystal device
2
with a lower surface
14
facing the surface
3
, and a light source
6
disposed along an end surface
5
of the transparent substrate
4
. The transparent substrate
4
is made of a highly light-transmissible material, shaped like a flat plate and substantially rectangular in section. A light reflection pattern
15
is formed on a surface
13
(an upper surface) of the transparent substrate
4
. The light reflection pattern
15
is formed parallel to the end surface
5
and composed of a plurality of grooves
16
substantially triangular in section and a plurality of flat portions
17
adjacent to the grooves
16
. In order to uniform light emitted from the light source
6
, the ratio of the width of the grooves
16
to the width of the flat portions
17
is set to increase in proportion to the increase in distance from the end surface
5
of the transparent substrate
4
.
The light source
6
is generally composed of a bar-like light conductive member
7
made of a transparent material and disposed along and close to the end surface
5
of the transparent substrate
4
, and a spot-like light source
8
disposed facing one end of the light conductive member
7
. Moreover, an optical path conversion means
11
is provided on the light conductive member
7
. The optical path conversion means
11
is formed on a surface
10
opposing a surface
9
facing the end surface
5
of the transparent substrate
4
such that grooves, for example, triangular in section run in the thickness direction of the transparent substrate
4
, or that surface roughening is partially provided whereby light emitted from the spot-like light source
8
is made incident on the end surface
5
of the transparent substrate
4
in a substantially uniform manner. Further, in order to achieve a uniform emission of light from the bar-like light conductive member
7
, the depth of the grooves triangular in section preferably increases in proportion to the increase in distance from the spot-like light source
8
.
Also, in
FIG. 5
, two light sources
6
are disposed along and parallel to the end surface
5
of the transparent substrate
4
(hereinafter one located far from the transparent substrate
4
is referred to as “outer light source” and the other located close to the transparent substrate
4
as “inner light source”). Light emitted from the outer light source
6
passes through the light conductive member
7
of the inner light source and enters the end surface
5
of the transparent substrate
4
. Thereby, the amount of light incident on the transparent substrate
4
is increased, and the brightness of the screen can be improved compared with a case where only one light source
6
is provided.
Further, as in a spread illuminating apparatus
1
″ shown in
FIG. 6
, two light sources
6
may be disposed along both the end surface
5
of the transparent substrate
4
and an end surface
25
opposite to the end surface
5
, respectively. In this case, the ratio of the width of the grooves
16
to the width of the flat portions
17
is set to be maximum at a center portion of the transparent substrate
4
. In addition, in order to introduce a still larger amount of light from the light source
6
into the transparent substrate
4
, a light reflection member
19
may be provided so as to cover the respective light conductive members
7
.
The light conductive member
7
is formed into a wedge-shape in such a manner that the area of an end surface
12
′ opposite to an end surface
12
facing the spot-like light source
8
is smaller than that of the end surface
12
, whereby light leakage at the end surface
12
′ is reduced. Accordingly, light enters efficiently the transparent substrate
4
, thereby improving the brightness of the screen. Here, in the wedge-shaped light conductive member, an end including the end surface
12
having a larger area is referred to as a “large end”, and another end including the end surface
12
′ having a smaller area is referred to as a “small end”.
The spread illuminating apparatuses
1
′ and
1
″ shown in
FIGS. 5 and 6
, respectively, include the following problems. Specifically, the two light sources
6
are disposed at the respective end surfaces
5
and
25
of the transparent substrate
4
for the purpose of improving the brightness of the screen. And, light emitted from the outer light source
6
of the two light sources
6
disposed parallel to each other passes through the light conductive member
7
of the inner light source
6
and enters the end surface
5
of the transparent substrate
4
.
However, light which is emitted from the outer light source
6
passes through the light conductive member
7
of the inner light source
6
and enters the end surfaces
5
,
25
and light which is emitted from the inner light source
6
, travels in the light conductive member
7
of the inner light source
6
and enters the end surface
5
,
25
interfere with each other. This generates interference fringes resulting in that intensity of light entering the transparent substrate
4
is made non-uniform in the longitudinal direction of the light source
6
. Further, disposition of the two light sources
6
in parallel at the respective end surfaces
5
and
25
of the transparent substrate
4
is unfavorable in view of a demand for downsizing the light source, and effective countermeasures have been desired.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above, and an object of the present invention is therefore to realize uniform light emission and high brightness as well in the spread illuminating apparatus while not increasing the size of the light source so as to meet the recent demand for downsizing and power saving.
According to a first aspect of the present invention to solve the above problems, in a spread illuminating apparatus of side light type having two bar-like light sources disposed on an end surface of a transparent substrate made of a light-transmissible material, the two light sources each comprising a bar-like light conductive member made of a transparent material and a spot-like light source disposed at one end of the light conductive member are disposed to overlap with each other in the thickness direction of the transparent substrate with respective spot-like light sources opposing each other.
In accordance with the present invention, light emitted from one spot-like light source into one light conductive member of the two directly therefrom enters the transparent substrate without passing through the other light conductive member and vice versa. Thus, light coming out from the one light conductive member and light coming out from the other light conductive member do not interfere with each other so as to prevent genera
Alavi Ali
Minebea Co. Ltd.
O'Shea Sandra
Oliff & Berridg,e PLC
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