Title: Back light module
Abstract: An improved back light module that the special design of light guide plate can prevent from the non-uniform of illumination. The module includes a light source; a reflector below the light source to reflect back the downward light rays for increasing the illumination of the back light module; and a light guide plate above said light source that a first portion of the bottom surface of said light guide plate, which is over said light source, is a plane and a second portion of the bottom/top surface of said light guide plate, which is not over said light source, has a plurality of regular bumps/recesses for focusing the light rays to increase the illumination, wherein said first portion and said second portion are arranged alternately in order.
Patent Number: 6,843,582 Issued on 01/18/2005 to Chang
| Inventors:
|
Chang; Yi-Hui (Hsinchu, TW)
|
| Assignee:
|
Toppoly Optoelectronics Corp. (TW)
|
| Appl. No.:
|
422725 |
| Filed:
|
April 25, 2003 |
| Current U.S. Class: |
362/240; 362/244; 362/245; 362/329 |
| Intern'l Class: |
F21V 005/00 |
| Field of Search: |
362/29,31,328,329,330,339,332,331,235,237,240,244,245,225,336
|
References Cited [Referenced By]
U.S. Patent Documents
| 5128783 | Jul., 1992 | Abileah et al. | 349/162.
|
| 5384658 | Jan., 1995 | Ohtake et al. | 359/707.
|
| 6578990 | Jun., 2003 | Hildenbrand et al. | 362/341.
|
| 6666569 | Dec., 2003 | Obata | 362/339.
|
Primary Examiner: Sember; Thomas M.
Attorney, Agent or Firm: Lowe Hauptman Gilman & Berner, LLP
Claims
What is claimed is:
1. An improved back light module, comprising:
a light source;
a reflector below said light source to reflect back the downward light rays
for increasing the illumination of said back light module; and
a light guide plate above said light source that a first portion of the
bottom surface of said light guide plate, which is over said light source,
is a plane and a second portion of the bottom surface of said light guide
plate, which is not over said light source, has a plurality of regular
bumps for focusing the light rays to increase the illumination, wherein
said first portion and said second portion are arranged alternately in
order.
2. The improved back light module according to claim 1, wherein said light
source includes CCFL (Cold Cathode Fluorescent Lamp).
3. The improved back light module according to claim 1, wherein said light
source includes LED (light emitting diode).
4. The improved back light module according to claim 1, wherein the
material of said light guide plate is PMMA.
5. The improved back light module according to claim 1, wherein the
material of said light guide plate is plastic division.
6. The improved back light module according to claim 1, wherein said light
guide plate has a plurality of TiO.sub.2 diffusion grains whose total
volume is between about 50%.about.80% of said light guide plate.
7. The improved back light module according to claim 1 further comprising a
diffusor sheet on said light guide plate.
8. The improved back light module according to claim 1 further comprising a
prism sheet on said light guide plate.
9. The improved back light module according to claim 1, wherein said first
portion further comprises a matted surface thereon.
10. The improved back light module according to claim 1, wherein said first
portion further comprises a shined surface thereon.
11. The improved back light module according to claim 10, wherein said
shined surface is a metal formed in sputtering way.
12. The improved back light module according to claim 11, wherein said
metal is selected from the group consisting of silver and aluminum.
13. The improved back light module according to claim 10, wherein said
shined surface is a metal formed in vapor deposition way.
14. The improved back light module according to claim 13, wherein said
metal is selected from the group consisting of silver and aluminum.
15. An improved back light module, comprising:
a light source;
a reflector below said light source to reflect back the downward light rays
for increasing the illumination of said back light module; and
a light guide plate above said light source, wherein a first portion of the
top surface of said light guide plate, which is over said light source, is
a plane and a second portion of the top surface of said light guide plate,
which is not over said light source, has a plurality of regular recesses
for focusing the light rays to increase the illumination, while said first
portion and said second portion are arranged alternately in order.
16. The improved back light module according to claim 15, wherein said
light source includes CCFL (Cold Cathode Fluorescent Lamp).
17. The improved back light module according to claim 15, wherein said
light source includes LED (light emitting diode).
18. The improved back light module according to claim 15, wherein the
material of said light guide plate is PMMA.
19. The improved back light module according to claim 15, wherein the
material of said light guide plate is plastic division.
20. The improved back light module according to claim 15, wherein said
light guide plate has a plurality of TiO.sub.2 diffusion grains whose
total volume is between about 50%.about.80% of said light guide plate.
21. The improved back light module according to claim 15 further comprising
a diffusor sheet on said light guide plate.
22. The improved back light module according to claim 15 further comprising
a prism sheet on said light guide plate.
23. The improved back light module according to claim 15, wherein said
first portion further comprises a matted surface thereon.
24. The improved back light module according to claim 15, wherein said
first portion further comprises a shined surface thereon.
25. The improved back light module according to claim 24, wherein said
shined surface is a metal formed in sputtering way.
26. The improved back light module according to claim 25, wherein said
metal is selected from the group consisting of silver and aluminum.
27. The improved back light module according to claim 24, wherein said
shined surface is a metal formed in vapor deposition way.
28. The improved back light module according to claim 27, wherein said
metal is selected from the group consisting of silver and aluminum.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a back light module, more particularly to a back
light module for large LCD device.
2. Description of the Prior Art
Among all kinds of flat display devices, a liquid crystal display (LCD)
device with low electrical power consumption, low voltage operation, thin
thickness and light weight, is widely used in nowadays. But an additional
light module is needed for LCD device to show figures or pictures on the
screen under the dark circumstance because liquid crystal does not have
the character of light-emitting itself. Because most of the power (about
70%) is consumed by the light module for notebook, it is very important
how to increase the illumination of light module or get the same
illumination by using the lower power light source for upgrading the
efficiency of light module and decreasing the consumed power.
Please refer to FIG. 1, a cross-sectional view of conventional structure of
back light module 110 for large LCD device is shown. It comprises a light
source 112; a light guide plate (LGP) 114; a reflector 116; a diffusor
sheet 118; and a diffusor sheet 120. The light source 112 can be
constituted by a row of cold cathode fluorescent lamp (CCFL) or an array
of light emitting diode (LED). The material of light guide plate 114 is
usually PMMA or plastic division with TiO.sub.2 diffusion grains whose
total volume is between about 50%.about.80% of light guide plate. The
light rays are well distributed when they are collided with the TiO.sub.2
diffusion grains. The reflector 116 is placed below the light guide plate
114 to reflect the downward light rays back into the light guide plate 114
for increasing the illumination of back light module 110. Besides, there
are sequentially diffusor sheets 118 and prism sheets 120 on the light
guide plate 114 for the light rays emitted from the light-emitting surface
of light guide plate 114 can be further well distributed into the panel of
liquid crystal device (not shown). The numbers of diffusor sheets and
prism sheets are decided on the design of back light module 110.
The wave nature of light is well known now, so the obvious "interference"
phenomenon is observed in the bottom surface of light guide plate 114 for
the light rays emitted from the light source 112, as shown in FIG. 2.
Sometimes the light rays meet in step (or in phase; constructive
interference), sometimes they meet out of step (or out of phase;
destructive interference), and sometimes they meet partially in step. When
the light rays meet in step, they add together due to constructive
interference and a bright fringe is displayed on the screen. In areas
where the light rays meet totally out of step, they will subtract from
each other due to destructive interference and a dark fringe will appear
in the bottom surface of light guide plate 114. FIG. 3 is the enlarged
view of the section A in FIG. 2. Similarly, the obvious "interference"
phenomenon is still observed when the light source is constituted by an
array of light emitting diode (LED).
Besides, a cold cathode fluorescent lamp (CCFL) is a line light source and
a light emitting diode (LED) is point light source, so the illumination of
light rays emitted from the above light source decreases when they travel
longer distances. The maximum illumination on the section of light guide
plate above the light source is got because the distance between the above
both is shortest and the illumination on other section of light guide
plate is smaller because the distance between the above both is longer.
Therefore, a problem that the illumination on the bottom surface of light
guide plate not well distributed is produced.
SUMMARY OF THE INVENTION
In the light of the state of the art described above, it is an object of
the present invention to provide an improved back light module for large
LCD device which is immune to the problems of the conventional back light
module for large LCD device described above.
It is another object of this invention to provide an improved back light
module for large LCD device that the special design of the top or bottom
surface of the light guide plate can make the light rays emitted from the
light source well distributed.
In view of the above and other objects which will become apparent as the
description proceeds, there is provided according to a general aspect of
the present invention an improved back light module which comprises a
light source; a reflector below said light source to reflect back the
downward light rays for increasing the illumination of said back light
module; a light guide plate above said light source that a first portion
of the bottom surface of said light guide plate, which is over said light
source, is a plane and a second portion of the bottom surface of said
light guide plate, which is not over said light source, has a plurality of
regular bumps for focusing the light rays to increase the illumination,
wherein said first portion and said second portion are arranged
alternately in order.
Based on the idea described above, wherein said light source includes CCFL
(Cold Cathode Fluorescent Lamp).
Based on the aforementioned idea, wherein said light source includes LED
(light emitting diode).
Based on the idea described above, wherein the material of said light guide
plate is PMMA.
Based on the aforementioned idea, wherein the material of said light guide
plate is plastic division.
Based on the idea described above, wherein said light guide plate has a
plurality of TiO.sub.2 diffusion grains whose total volume is between
about 50%.about.80% of said light guide plate.
Based on the idea described above, the improved back light module further
comprises a diffusor sheet on said light guide plate.
Based on the aforementioned idea, the improved back light module further
comprises a prism sheet on said light guide plate.
Based on the idea described above, wherein said first portion further
comprises a matted surface thereon.
Based on the aforementioned idea, wherein said first portion further
comprises a shined surface thereon.
Based on the idea described above, wherein said shined surface is a metal
formed in sputtering way.
Based on the aforementioned idea, wherein said metal is selected from the
group consisting of silver and aluminium.
Based on the idea described above, wherein said shined surface is a metal
formed in vapor deposition way,
Based on the aforementioned idea, wherein said metal is selected from the
group consisting of silver and aluminium.
In view of the above and other objects which will become apparent as the
description proceeds, there is provided according to a general aspect of
the present invention an improved back light module which comprises a
light source; a reflector below said light source to reflect back the
downward light rays for increasing the illumination of said back light
module; a light guide plate above said light source that a first portion
of the top surface of said light guide plate, which is over said light
source, is a plane and a second portion of the top surface of said light
guide plate, which is not over said light source, has a plurality of
regular recesses for focusing the light rays to increase the illumination,
wherein said first portion and said second portion are arranged
alternately in order.
Based on the idea described above, wherein said light source includes CCFL
(Cold Cathode Fluorescent Lamp).
Based on the aforementioned idea, wherein said light source includes LED
(light emitting diode).
Based on the idea described above, wherein the material of said light guide
plate is PMMA.
Based on the aforementioned idea, wherein the material of said light guide
plate is plastic division.
Based on the idea described above, wherein said light guide plate has a
plurality of TiO.sub.2 diffusion grains whose total volume is between
about 50%.about.80% of said light guide plate.
Based on the idea described above, the improved back light module further
comprises a diffuser sheet on said light guide plate.
Based on the aforementioned idea, he improved back light module further
comprises a prism sheet on said light guide plate.
Based on the idea described above, wherein said said first portion further
comprises a matted surface thereon.
Based on the aforementioned idea, wherein said first portion further
comprises a shined surface thereon.
Based on the idea described above, wherein said shined surface is a metal
formed in sputtering way.
Based on the aforementioned idea, wherein said metal is selected from the
group consisting of silver and aluminum.
Based on thee idea described above, wherein said shined surface is a metal
formed in vapor deposition way.
Based on the aforementioned idea, wherein said metal is selected from the
group consisting of silver and aluminum.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing aspects and many of the attendant advantages of this
invention will become more readily appreciated as the same becomes better
understood by reference to the following detailed description, when taken
in conjunction with the accompanying drawings, wherein:
FIG. 1 illustrates a cross-sectional view of conventional structure of back
light module for large LCD device;
FIG. 2 illustrates a perspective view of conventional structure of back
light module for large LCD device;
FIG. 3 illustrates an enlarged view of the section A in FIG. 2;
FIG. 4 illustrates a cross-sectional view of back light module for large
LCD device according to the first embodiment of the present invention;
FIG. 5 illustrates an enlarged cross-sectional view of back light module
for large LCD device according to the first embodiment of the present
invention; and
FIG. 6 illustrates an enlarged cross-section view of back light module for
large LCD device according to the second embodiment of the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Some sample embodiments of the present invention will now be described in
greater detail. Nevertheless, it should be recognized that the present
invention can be practiced in a wide range of other embodiments besides
those explicitly described, and the scope of the present invention is
expressly not limited except as specified in the accompanying claims.
The first embodiment according to this invention is referred to FIG. 4 and
FIG. 5. Please refer to FIG. 4, a cross-sectional view of back light
module 10 for large LCD device according to the present invention is
shown. It comprises a light source 12; a light guide plate (LGP) 14; a
reflector 16; a diffusor sheet 18; and a diffusor sheet 20. The light
source 12 can be constituted by a row of cold cathode fluorescent lamp
(CCFL) or an array of light emitting diode (LED). The material of light
guide plate 14 is usually PMMA or plastic division with TiO.sub.2
diffusion grains 22 whose total volume is between about 50%.about.80% of
light guide plate. The light rays are well distributed when they are
collided with the TiO.sub.2 diffusion grains. The reflector 16 is placed
below the light guide plate 14 to reflect the downward light rays back
into the light guide plate 14 for increasing the illumination of back
light module 10. Besides, there are sequentially diffusor sheets 18 and
prism sheets 20 on the light guide plate 14 in order to the light rays
emitted from the light-emitting surface of light guide plate 14 can be
further well distributed into the panel of liquid crystal device (not
shown). The numbers of diffusor sheets and prism sheets are decided on the
design of the back light module 10.
The bottom surface of light guide plate changed from the fully inclined
plane to the plane including several bumps is the main difference between
the first embodiment according to the present invention and the
conventional structure of back light module for solving the problem of the
light rays that enter into the light guide plate not well distributed. As
shown in FIG. 5, the section 24 of the bottom surface of light guide plate
14 above the light source 12 still remains plane surface, in other words,
the illumination of the section 24 is not changed. The other section 26 of
the bottom surface of light guide plate 14 includes several bumps for
gathering the light rays to increase the illumination of the section 26
now. So the light rays emitted from the light source 12 enter into the
bottom surface of light guide plate 14 are well distributed. It can
prevent from the appearance of the light and dark fringes. Besides, the
section 24 can be dealt with the matte or shiny process to decrease or
reflect the illumination thereof for the light rays emitted from the light
source 12 enter into the bottom surface of light guide plate 14 are
further well distributed. The section 24 is coated with a metal by the
vapor deposition method or the sputtering method in the shiny process. We
can use aluminum as the metal material when the lower reflective condition
is asked and silver as the metal material when the higher reflective
condition is asked.
Please refer FIG. 6, an enlarged cross-section view of back light module
for large LCD device according to the second embodiment of the present
invention. The section 28 of the top surface of light guide plate 14 above
the light source 12 still remains plane surface, in other words, the
illumination of the section 28 is not changed. The other section 30 of the
top surface of light guide plate 14 includes several recesses for
gathering the light rays to increase the illumination of the section 30
now. So the light rays emitted from the light source 12 enter into the top
surface of light guide plate 14 are well distributed. Similarly, the
section 28 can be dealt with the matte or shiny process to decrease or
reflect the illumination thereof for the light rays emitted from the light
source 12 enter into the top surface of light guide plate 14 are further
well distributed. The section 28 is coated with a metal by the vapor
deposition method or the sputtering method in the shiny process. We can
use aluminum as the metal material when the lower reflective condition is
asked and silver as the metal material when the higher reflective
condition is asked.
Although the specific embodiment has been illustrated and described, it
will be obvious to those skilled in the art that various modifications may
be made without departing from what is intended to be limited solely by
the appended claims.
*
