Illumination – Revolving
Reexamination Certificate
2002-03-18
2003-04-01
Cariaso, Alan (Department: 2875)
Illumination
Revolving
C362S027000, C362S331000, C349S062000, C385S901000
Reexamination Certificate
active
06540368
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 more particularly for a liquid crystal display device.
2. Description of the Related Art
A liquid crystal display device characterized by low profile, small occupied volume, light weight, etc. has been extensively used in electric products including mobile phones and personal computers, and the demand therefor has been increased. However, since a liquid crystal of the liquid crystal display device emits no light itself, an illuminating apparatus must be provided when the liquid crystal display device is used in dark places where the solar or illumination light is not fully available. Thus, this illuminating apparatus is also desired to be compact and small in power consumption, and there has been a growing tendency to employ a low profile spread illuminating apparatus of side light type (light conductive member type).
FIG. 5
shows an embodiment of a conventional spread illuminating apparatus of side light type. As shown in the figure, a spread illuminating apparatus
1
′ is generally composed of a transparent substrate
2
made of a light-transmissible material and at least one bar-like light source
5
disposed close to at least one of end surfaces
8
and
18
of the transparent substrate
2
. The light source
5
is composed of a bar-like light conductive member
3
made of a transparent material and a spot-like light source (for example, a light-emitting diode)
4
disposed facing an end face
7
of the light conductive member
3
. Light emitted from the light source
5
is guided into the transparent substrate
2
to irradiate a liquid crystal display device (not shown) disposed under the transparent substrate
2
.
A light reflection pattern
49
is formed on an upper surface
46
of the transparent substrate
2
. The light reflection pattern
49
is composed of grooves
47
each shaped triangular in section and running parallel to the longitudinal direction of the light conductive member
3
and flat portions
48
each formed between two adjacent grooves
47
. The grooves
47
are set to have respective depths different from one another so that light guided in from the light conductive member
3
is reflected in a substantially uniform manner everywhere at the transparent substrate
2
irrespective of the distance from the light conductive member
8
to irradiate the liquid crystal display device (not shown) provided under the transparent substrate
2
. Specifically, the depth of the grooves
47
gradually increases in proportion to the increase in distance from the light conductive member
3
. The grooves
47
of the light reflection pattern
49
formed on the transparent substrate
2
are very minute and cannot be visually noticeable when observing the screen.
An optical path conversion means
12
′ comprising grooves
15
′ triangular in section and running parallel to the thickness direction of the light conductive member
3
and flat portions
16
′ is provided on a surface
10
of the light conductive member
3
opposite to a surface
9
facing the end surface
8
of the transparent substrate
2
. This optical path conversion means
12
′ has a function to allow light emitted from the spot-like light source
4
to be made incident on the end surface
8
of the transparent substrate
2
in a substantially uniform manner. The light conductive member
3
is disposed such that the surface
9
thereof faces the end surface
8
of the transparent substrate
2
with a predetermined distance therebetween.
A light reflection member (frame)
13
is provided around the light conductive member
3
in order that light emitted from the spot-like light source
4
is fully utilized to be directed into the transparent substrate
2
. The light reflection member
13
is substantially U-shaped in section, disposed so as to cover longitudinal surfaces of the light conductive member
3
except the surface
9
facing the transparent substrate
2
and further the upper and lower surfaces of the transparent substrate
2
at the vicinity of the end surface
8
, and is adapted to recover light leaking from the light conductive member
3
.
However, with the optical path conversion means
12
′ described above, light emitted from the spot-like light source
4
is mostly reflected only at the grooves
15
′ to be guided into the transparent substrate
2
, irradiating the transparent substrate
2
with many light rays L, and stripe-like fringes appear on a viewing surface as shown in FIG.
6
. To overcome such a disadvantage, the applicant of the present invention proposed an optical path conversion means
12
″ having grooves
15
″ formed with a predetermined inclination angle with respect to the thickness direction of the light conductive member
3
as shown in
FIG. 7
so as to increase an irradiation range per groove thereby realizing uniform light emission (Japanese Patent Application No. 2001-287341).
The optical path conversion means
12
″ shown in
FIG. 7
is effective in softening stripe-like fringes on the viewing surface, but the brightness of the screen decreases due to the inclination angle of the grooves
15
″. When the grooves
15
″ are shaped substantially triangular or trapezoidal in section, the uniformity of light emission on the screen improves as the inclination angle of the grooves
15
″ increases. However, the brightness of the screen decreases as the inclination angle of the grooves
15
″ increases, and when the inclination angle exceeds a predetermined value, the brightness of the screen decreases in a greater degree than when a diffusion plate is inserted between the light conductive member and the transparent substrate to improve the uniformity of the light emitted from the screen, which was disclosed by the applicant of the present invention in Japanese Patent Laid-open No. 2000-231814. This comes from that, since the grooves
15
″ have flat surfaces, the inclination of the light reflected at the grooves
15
″ also increases as the inclination angle of the grooves
15
″ increases, thereby reducing the amount of the light reflected at the grooves
15
″ which, without repeated reflection in the light conductive member
3
, is guided directly into the transparent substrate
2
. The light made incident on the surface of the light conductive member
3
at an angle exceeding the critical angle leaks outside, or is reflected by the light reflection member
13
disposed covering the light conductive member
3
to return into the light conductive member
3
. In either case, the light suffers loss with the brightness decreased
SUMMARY OF THE INVENTION
The present invention has been made in the light of the above problems and the object of the present invention is to provide a spread illuminating apparatus to simultaneously realize uniform and increased brightness over the whole screen.
In order to solve the above problems, according to a first aspect of the present invention, in a spread illuminating apparatus of side light type, comprising a transparent substrate made of a light-transmissible material; and at least one bar-like light source composed of a bar-like light conductive member and at least one spot-like light source provided at an end thereof, and disposed close to an end surface of the transparent substrate, the bar-like light conductive member is a multi-layer light conductive member composed of a plurality of plate-like light conductive members put into lamination, and an optical path conversion means is provided on a side surface of each of the plate-like light conductive members. Since the plurality of plate-like light conductive members having respective optical path conversion means are put into lamination, an optical path conversion means of the light conductive member multi-layered can be constituted by the combination of the configuration of
Alavi Ali
Cariaso Alan
Minebea Co. Ltd.
Oliff & Berridg,e PLC
LandOfFree
Spread illuminating apparatus with multi-layer light... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Spread illuminating apparatus with multi-layer light..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Spread illuminating apparatus with multi-layer light... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3094228