Illumination – Revolving
Reexamination Certificate
2000-06-26
2001-08-28
Cariaso, Alan (Department: 2875)
Illumination
Revolving
C362S551000, C362S558000
Reexamination Certificate
active
06280044
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spread illuminating apparatus as an illuminating means for signboards, various kinds of reflection-type displays and so on, in particular, as an illuminating means for a liquid crystal display.
2. Related Art
As an auxiliary illuminating apparatus for illuminating a screen of a reflection-type liquid crystal display uniformly, the present inventors proposed the spread illuminating apparatus (patent application Ser. No. 182076/98), an outline of which will be explained hereinafter with reference to FIG.
4
. This illuminating apparatus
1
is disclosed as a prior art. The spread illuminating apparatus
1
is disposed to cover a screen F (front surface) of a reflection-type liquid crystal display element L. The apparatus comprises a plate-like transparent substrate
2
rectangular in section and made of a highly light permeable material, and a light source portion
4
provided close to one end surface
3
of the transparent substrate
2
. The transparent substrate
2
may be wedge-shaped for reducing its weight. Here, in
FIG. 4
, one surface of the transparent substrate
2
abutting on the reflection-type liquid crystal element L will be denoted as a lower surface
5
and a viewing surface (screen) on the opposite surface as an upper surface (front surface)
6
.
As shown in
FIG. 5
, the light source portion
4
is formed with a bar-like light conductive member
7
and spot-like light sources
9
such as light emitting diodes provided to both ends
8
of the light conductive member
7
. An optical path conversion means
11
to be explained later in details is formed on one surface of the light conductive member
7
, whose longitudinal surfaces except the one opposing the transparent substrate
2
are covered with a light reflection member (reflector)
12
in order to introduce light beams traveling through the light conductive member
7
into the transparent substrate
2
in a high degree of efficiency.
The optical path conversion means
11
is formed on a surface
14
opposite to a surface
13
facing the end surface
3
of the transparent substrate
2
, and comprises a light dispersion portion
15
(black portion in
FIG. 5
) with a partial coarsening work to form a minutely rugged portion and a plane portion
16
without the coarsening work. Since light beams reflected by the light dispersion portion
15
exit out the surface
13
and enter the transparent substrate
2
in a larger amount than those by the plane portion
16
due to the formation of the minutely rugged portion, the light dispersion portion
15
is so formed as to increase its area as it gets away from the spot-like light source
9
.
Thus, the optical path conversion means
11
is formed in consideration of a balance between the distance from the spot-like light source
9
and the area of the light dispersion portion
15
, whereby the light beams are uniformly emitted from the surface
13
facing the end surface
3
of the transparent substrate
2
in spite of the fact that the spot-like light source
9
is provided to the end portion
8
of the light conductive member
7
, so the light source portion
4
formed with the spot-like light source
9
and the light conductive member
7
functions similar to a fluorescent lamp (cold cathode fluorescent and hot cathode fluorescent lamps, etc.) as a bar-like light source.
And, a light reflection pattern
17
is formed on the upper surface
6
of the transparent substrate
2
. The light reflection pattern
17
is constituted with a number of grooves
18
approximately triangular in section and plane portions
19
adjacent to the grooves
18
formed along the end surface
3
. The light reflection pattern
17
is formed so that the interval between the grooves
18
varies from spot to spot in order to achieve a uniform emitting of spread illumination from the transparent substrate
2
independent of the distance from the light source
4
. That is, the ratio of the width (occupied area) of the groove
18
to the width (occupied area) of the plane portion
19
is set to gradually increase as the groove
18
gets away from the end surface
3
of the transparent substrate
2
. For reference, since the grooves
18
of the light reflection pattern
17
formed on the transparent substrate
2
are quite minute, they cannot be visually recognized when viewing a screen.
When such a spread illuminating apparatus
1
is disposed in such a manner as to cover the upper surface of the reflection-type liquid crystal element L, the light beams emitted from the light source portion
4
enter the transparent substrate
2
from the end surface
3
, and travel toward the opposite surface
10
as they repeat reflection and refraction therein. Meanwhile, the light beams emitted from the lower surface
5
of the transparent substrate
2
illuminate the reflection-type liquid crystal element L, thereby brightening the screen. Since the amount of light emitted from the lower surface
5
is approximately uniform independent of the distance from the light source portion
4
due to the formation of the light reflection pattern
17
, the reflection-type liquid crystal element L can be illuminated in a spread manner.
And, although the spot-like light source
9
is provided to both ends
8
,
8
of the light conductive member
7
respectively in
FIGS. 4 and 5
, it may be provided to either one end
8
. Moreover, the above discussed optical path conversion means
11
formed on the light conductive member
7
is constituted with a light dispersion portion
15
consisting of a minutely rugged surface and a plane portion
16
, but it can be alternately constituted with a portion coated with material containing light dispersion substance and a portion without such a coating, or with a portion with a groove whose reflection angle is set to make reflected light beams enter the transparent substrate
2
and a portion without such a groove.
Now, since the light source portion
4
of the spread illuminating apparatus
1
is formed with the light conductive member
7
and the spot-like light source
9
, there has been such a problem as mentioned below. That is, when viewing the screen on the above described spread illuminating apparatus
1
disposed to cover the viewing surface F of the liquid crystal display L, it was found that a stripe pattern of brightness and darkness can be generated orthogonally to the end surface
3
, which prevents a uniform spread emitting, causing difficulty in viewing the screen.
This stripe pattern of brightness and darkness was found to be caused by the optical path conversion means
11
provided on the light conductive member
7
. That is, while most of the light beams reflected on the light dispersion portion
15
of the optical conversion means
11
exit out the surface
13
and travel into the transparent substrate
2
, most of the light beams reflected on the plane portion
16
do not exit out the surface
13
due to a total reflection, so, depending on the condition settled in the light reflection pattern consisting of the light dispersion portion
15
and the plane portion
16
, the brightness of the light emitted from the surface
13
becomes uneven. In this case, since the brightness of the light beams entering the transparent substrate
2
is not uniform, the stripe pattern of brightness and darkness orthogonal to the end surface
3
is generated on the screen.
The present invention has been made in the light of the above problem, and an object thereof is to make uniform the brightness of the light beams entering the transparent substrate for achieving a uniform spread illumination in a spread illuminating apparatus.
In order to solve the above problem, according to a first aspect of the present invention, in a side light type of a spread illuminating apparatus in which a bar-like light source is provided close to an end surface of a transparent substrate made of light permeable material, the bar-like light source is formed with a light conductive member made of the light permeable m
Cariaso Alan
Minebea Co. Ltd.
Oliff & Berridg,e PLC
Sawhney Hargobind S.
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