Illumination – Revolving
Reexamination Certificate
2000-08-08
2002-09-10
O'Shea, Sandra (Department: 2875)
Illumination
Revolving
C362S026000, C362S146000
Reexamination Certificate
active
06447136
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light guide plate, and more particularly to a light guide plate for a backlight system used in a liquid crystal display.
2. Description of the Related Art
For the sake of comparison, a conventional backlight system of a liquid crystal display will be previously described in the following with reference to
FIGS. 1
to
3
.
Referring to
FIG. 1
, a conventional backlight system of a liquid crystal display includes a lamp
11
, a light guide plate
12
, a lamp reflector
13
, and a back reflector
14
.
The lamp
11
is used as a light source to provide the backlight system with the necessary light beams.
The light guide plate
12
has a front surface
121
, a back surface
122
, and a side surface
123
that is adjacent to the lamp
11
. In addition, the side surface
123
is disposed to be parallel with the lamp
11
so as to receive the light beams irradiated by the lamp
11
. The back surface
122
is provided with a plurality of reflector dots
124
, each of which is designed as a hemispherical protrusion.
The lamp reflector
13
is disposed to surround the lamp
11
in such a way that the light beams irradiated by the lamp
11
is reflected toward the light guide plate
12
.
The back reflector
14
is disposed on the back surface
122
of the light guide plate
12
to thereby reflect back the light beams transmitting out of the back surface
122
of the light guide light
12
.
As shown in
FIG. 1
, in normal situations, a light beam B irradiated from the lamp
11
through the side surface
123
into the light guide plate
12
is totally reflected back and forth between the front surface
121
and the back surface
122
in such a way of propagating away from the lamp
11
. In this case, there are no light beams refracted out of the front surface
121
of the light guide plate
12
. However, if a light beam A irradiated from the lamp
11
hits against any of the reflection dots
124
during propagating, a reflective light beam A
1
refracts out of the front surface
121
as a result of a change of the reflective angle of the light beam A. With the disposition of the reflector dots described above, the backlight necessary for a panel
17
of the liquid crystal display is thereby provided.
As a conventional method for fabricating the reflector dots
124
of the light guide plate
12
, a halftone printing process is used to print a high reflective material over the back surface
122
of the light guide plate
12
, thereby forming the reflector dots
124
. Undesirably, the manufacturing of the back light system used in the liquid crystal display takes a long time and costs expensively due to the requirement of the halftone printing process.
As another conventional method for fabricating the reflector dots
124
of the light guide plate
12
, a plurality of reflector dots
124
are directly fabricated as an integral part of the light guide plate
12
on the back surface
122
. For example, each of the reflector dots
124
may be shaped like a hemisphere, a trapezoid, a pyramid, or a half-moon. However, the trapezoid and half-moon reflector dots only reflect out of the front surface
121
the incident light beams propagating in a certain direction. Therefore, these reflector dots are not applicable to a condition that the incident light beams propagate in a number of directions. Although the hemispherical reflector dots are applicable to a condition that the incident light beams propagate in a number of directions, their ability to reflect and refract the light beams out of the light guide plate is still not optimum as described below.
Referring to FIGS.
2
(
a
) and
2
(
b
), each reflector dot
124
is designed as a hemispherical protrusion. Since each reflector dot
124
is no more than a single protrusion as observed in any directions, there is only a local reflection region capable of effectively reflecting and refracting the incident light beam out of the light guide plate. For example, only a local reflection region
126
is able to effectively reflect and refract out of the light guide plate the incident light beam propagating in the X direction. This is because only the local reflection region
126
can effectively change the reflective angle of the incident light beam propagating in the X direction.
Referring to
FIG. 3
, which is a three-dimensional view, when the light beam A hits against the reflection dot
124
, only part of the light beam A is reflected as a reflective light beam A
1
which is then refracted out of the front surface
121
of the light guide plate. Therefore, the reflecting efficiency of the conventional light guide plate still needs an improvement.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a light guide plate for a backlight system, which is applicable to a condition that the incident light beams propagate in a number of directions and is able to effectively reflect and refract the incident light beams out of the front surface of the light guide plate.
In order to achieve the object described above, a light guide plate for a backlight system according to the present invention is disclosed. The backlight system consists of a light guide plate, a lamp, a lamp reflector, and a back reflector. The lamp reflector is disposed to surround the lamp for reflecting the light beams irradiated by the lamp toward the light guide plate. The light guide plate has a front surface facing a panel; four end surfaces, one of which is disposed to face the lamp; and a back surface on which the back reflector is disposed. The back surface of the light guide plate is integrally formed with a plurality of reflector units. Each of the plurality of the reflector units includes at least an annular protrusion.
With the disposition of the plurality of reflector units described above, the light guide plate effectively reflects the incident light beams into at least two reflective light beams which are then refracted out of the front surface even if the incident light beams propagate in a number of directions. Therefore, the light guide plate according to the present invention achieves an excellent reflective efficiency.
REFERENCES:
patent: 5377084 (1994-12-01), Kojima et al.
patent: 5961198 (1999-10-01), Hira et al.
Hou Shi-chi
Hsieh Gin-wen
Liu Ming-dah
Pan Bor-jyh
Coretronic Corporation
Hsu Winston
Lee Guiyoung
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