US20070171626A1

US20070171626A1 - Direct type backlight module

Info

Publication number: US20070171626A1
Application number: US11/508,635
Authority: US
Inventors: Shao-Han Chang
Original assignee: Hon Hai Precision Industry Co Ltd
Current assignee: Hon Hai Precision Industry Co Ltd
Priority date: 2006-01-21
Filing date: 2006-08-23
Publication date: 2007-07-26
Also published as: CN101004515A; US20080192507A1; US7591578B2

Abstract

A direct type backlight module includes a diffusion plate, at least a lamp-fixing unit, at least a light source and a reflective plate. The lamp-fixing unit is disposed under one edge of the diffusion plate. The lamp-fixing unit includes an inner surface facing the inner area underneath the diffusion plate, an outer surface opposite to the inner surface, and a plurality of fin structures defined on the outer surface. The light source is fixed on the inner surface of the lamp-fixing unit. The reflective plate is disposed adjacent the lamp-fixing unit and under the diffusion plate, facing the light source. Light rays emitted from the light source being uniformly reflected toward the diffusion plate by the reflective plate. The present backlight module has a thin body and also has a good heat dissipation capability.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to co-pending U.S. patent applications, entitled “LIGHT SOURCE MODULE AND BACKLIGHT SYSTEM USING THE SAME”, by Shao-Han Chang and Fen Chen with Attorney Docket No. 14963-56245; entitled “BACKLIGHT MODULE”, by Shao-Han Chang with Attorney Docket No. 14963-56247; entitled “BACKLIGHT SYSTEM”, by Shao-Han Chang with Attorney Docket No. 14963-56248. Such applications have the same assignee as the present application and have been concurrently filed herewith. The disclosure of the above identified applications is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to backlight modules, more particularly, to direct type backlight modules for use in, for example, a liquid crystal display (LCD).

BACKGROUND

Most LCD devices are passive devices in which images are displayed by controlling an amount of light input from an outside light source. Thus, a separate light source (for example, backlight module) is generally employed for illuminating an LCD.
Generally, backlight modules can be classified into an edge type or a direct type based upon the location of lamps within the device. The edge type backlight module has a lamp unit arranged at a side portion of a light guiding plate that guides light. The edge type backlight modules are commonly employed in small-sized LCD due to their lightweight, small size, and low electricity consumption. However, the edge type backlight modules are not suitable for large-sized LCD (20 inches or more). A direct type backlight module has a plurality of lamps arranged in regular positions to directly illuminate an entire surface of an LCD panel. The direct type backlight modules have higher efficiency of light usage and longer operational lifetime than the edge type backlight modules, the direct type backlight modules are especially used in large-sized LCD devices. However, an LCD device usually employs a significant amount of lamps to reach a high luminance. The significant amount of lamps results in a great deal of heat produced and cumulated inside the LCD device. Therefore, heat dissipation of the direct type backlight modules is usually a hard nut to crack.
Referring to FIG. 9, a typical direct type backlight module 100 is shown. The backlight module 100 includes a frame 110, a diffusion plate 120, a heat dissipating plate 130, a reflective plate 140, and a plurality of lamp tubes 150. The frame 110 includes a base 112 and four sidewalls 114 that extend from the peripheral of the base 112, the base 112 and the sidewalls 114 cooperatively define a chamber 116. The heat dissipating plate 130 is disposed on the base 112 of the frame 110. The reflective plate 140 is positioned on the heat dissipating plate 130. The lamp tubes 150 are aligned in the chamber 116 above the reflective plate 140. The diffusion plate 120 is disposed on the frame 110 covering the chamber 116. The reflective plate 140 is used to reflect a part of light rays emitted from the lamp tubes 150 to the diffusion plate 120. The diffusion plate 120 is used to diffuse or reflect light rays by means of shielding, scattering, or refraction.
In order to decrease heat that reduces lifetime of the lamp tubes 150 and causes distortion of the diffusion plate 120 from accumulating in the chamber 116, the bottom surface of the base 112 defines a plurality of fin structures 118 thereon. Heat is efficiently dissipated out from the fin structures 118 via the heat dissipating plate 130. However, the thickness of the backlight module 100 is limited due to the physical properties of the frame 110. In addition, in order to enhance uniformity of light rays for the backlight module 100, there must be a big space between the diffusion plate 120 and the lamp tubes 150 for eliminating potential dark strips caused by the reduced intensity of light between adjacent lamp tubes 150. Therefore, the backlight module 100 suffers from increased thickness and decreased luminance due to exiting between the diffusion plate 120 and lamp tubes 150.
What is needed, therefore, is a direct type backlight module that overcomes the above mentioned shortcomings.

SUMMARY

A direct type backlight module according to a preferred embodiment includes a diffusion plate, at least a lamp-fixing unit, at least a light source and a reflective plate. The lamp-fixing unit is disposed under one edge of the diffusion plate. The lamp-fixing unit includes an inner surface facing an inner area underneath the diffusion plate, an outer surface opposite to the inner surface, and a plurality of fin structures defined on the outer surface. The light source is fixed on the inner surface of the lamp-fixing unit. The reflective plate is disposed adjacent the lamp-fixing unit and under the diffusion plate, facing the light source. Light rays emitted from the light source being uniformly reflected towards the diffusion plate by the reflective plate.
Other advantages and novel features will become more apparent from the following detailed description of the preferred embodiments, when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the direct type backlight module can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present direct type backlight module. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

FIG. 1 is a schematic, exploded isometric view of a direct type backlight module according to a first preferred embodiment;

FIG. 2 is a schematic, assembled isometric view of the direct type backlight module of FIG. 1;

FIG. 3 is a schematic, cross-sectional view taken along a III-III line of FIG. 1;

FIG. 4 is a schematic, cross-sectional view of a direct type backlight module according to a second preferred embodiment;

FIG. 5 is a schematic, cross-sectional view of a direct type backlight module according to a third preferred embodiment;

FIG. 6 is a schematic, cross-sectional view of a direct type backlight module according to a fourth preferred embodiment;

FIG. 7 is a schematic, cross-sectional view of a direct type backlight module according to a fifth preferred embodiment;

FIG. 8 is a schematic, cross-sectional view of a direct type backlight module according to a sixth preferred embodiment; and

FIG. 9 is a schematic, cross-sectional view of a conventional direct type backlight module.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to the drawings to describe preferred embodiments of the present back the space light module, in detail.
Referring to FIGS. 1 through 3, a direct type backlight module 200 in accordance with a first preferred embodiment is shown. The backlight module 200 includes a diffusion plate 210, a lamp-fixing unit 220, a light source 230, and a reflective plate 240. The lamp-fixing unit 220 is disposed under one edge of the diffusion plate 210. The lamp-fixing unit 220 includes an inner surface 221 facing an inner area underneath the diffusion plate 210, an outer surface 222 facing an opposite direction from to the inner surface 221, and a plurality of fin structures 225 defined on the outer surface 222 for increasing a heat radiation area and heat transfer efficiency. The light source 230 is fixed on the inner surface 221 of the lamp-fixing unit 220. The reflective plate 240 is disposed adjacent the lamp-fixing unit 220 and under the diffusion plate 210, facing the light source 230.
A longitudinal length of the lamp-fixing unit 220 aligns with an edge of the diffusion plate 210. The lamp-fixing unit 220 may be integrally manufactured. A material of the lamp-fixing unit 220 is selected from a group comprising of aluminum, magnesium, copper or their alloys, or other suitable materials having a good heat dissipation coefficient. In the illustrated embodiment, a material of the lamp-fixing unit 220 is aluminum. The light source 230 is light emitting diode (LED). The reflective plate 240 is a smooth curved sheet bent towards the diffusion plate 210 and the light source 230, the reflective plate 240 further has a reflective surface 241 facing the diffusion plate 210 and the light source 230. It is to be understood that the present backlight module may include a plurality of light sources for improving optical brightness.
Referring also to FIGS. 1 and 2, in order to improve heat dissipation capability of the backlight module 200, the lamp-fixing unit 220 further includes a first heat conductive layer 260 and an aluminum based printed circuit board 270 (PCB), sandwiched between the light source 230 and the inner surface 221 of the lamp-fixing unit 220. It is to be understood that the lamp-fixing unit 220 further includes a second heat conductive layer (not shown) sandwiched between the aluminum base PCB 270 and the light source 230.
Referring also to FIG. 1, the backlight module 200 further includes a frame 280 used for receiving the reflective plate 240 and also for supporting the diffusion plate 210. The frame 280 includes a rectangular base 281 according to the diffusion plate 210, and three sidewalls 283 extending perpendicularly from three edges excluding the edge aligned with the lamp-fixing unit 220 of the base 281. The light source 230 fixed on the lamp-fixing unit 220 faces an inner area of the frame 280. The diffusion plate 210 is positioned on a top of the sidewalls 283. A height of the sidewalls 283 is same as that of the lamp-fixing unit 220. The frame 280 can also help to increase light energy utilization rate by substantially containing light rays in a confined area (not labeled) defined by the lamp-fixing unit 220 and the frame 280.
In use, light rays from the light source 230 can be uniformly reflected onto the diffusion plate 210 by the reflective plate 240. Heat produced by the light source 230 can be efficiently dissipated out from the fin structures 225 via the first heat conductive layer 260 and the aluminum based PCB 270. In addition, because the lamp-fixing unit 220 with the light source 230 is positioned under one edge of the diffusion plate 210, most light rays from the light source 230 avoids projecting directly into the diffusion plate 210, thereby the present backlight module can be configured to be a thin body.
Referring to FIG. 4, a backlight module 300 in accordance with a second preferred embodiment is shown. The backlight module 300 is similar in principle to that of the first embodiment, except that an inner surface 321 of a lamp-fixing unit 320 is slanted inwards forming an inclined acute angle θ₁defined by the inner surface 321 of the lamp-fixing unit 320 with respect to a reflective plate 340. The inclined acute angle θ₁is chosen to be about 60 degrees. A curvature of the reflective plate 340 is chosen based upon a positioning of light source 330, thereby reflecting light rays emitted from a light source 330 uniformly into a diffusion plate 310.
Referring to FIG. 5, a backlight module 400 in accordance with a third preferred embodiment is shown. The backlight module 400 is similar in principle to that of the first embodiment, except that an inner surface 421 of a lamp-fixing unit 420 is slanted outwards forming an inclined obtuse angle θ₂defined by the inner surface 421 of a lamp-fixing unit 420 with respect to the reflective plate 440. The obtuse angle θ₂is chosen to be about 120 degrees. A curvature of the reflective plate 440 is chosen based upon a positioning of a light source 430, thereby reflecting light rays emitted from the light source 430 uniformly into a diffusion plate 410.
It is noted that, the angle of inclination of the inner surface with respect to the horizontal portion of the reflective plate is not limited to the above illustrated embodiments. An angle in the range from above about 30 degrees to about 150 degrees should be considered to be within the scope of the present invention.
Referring to FIG. 6, a backlight module 500 in accordance with a fourth preferred embodiment is shown. The backlight module 500 is similar in principle to that of the third embodiment, except that a lamp-fixing unit 520 of the backlight module 500 further includes an upper reflective portion 5211 and a bottom reflective portion 5215. The upper reflective portion 5211 includes a first protruding wall 5212 extending from a top of an inner surface 521 of the lamp-fixing unit 520 along a direction parallel to the diffusion plate 510 towards an inner area of the diffusion plate 510, a second protruding wall 5213 extending from a bottom surface of the first protruding wall 5212 toward the reflective plate 540 adjacent to the inner surface 521, the first protruding wall 5212 and the second protruding wall 5213 cooperatively defining a second reflective surface 5214 facing the reflective plate 540.
The bottom reflective unit 5215 includes a third protruding wall 5216 extending from a bottom of an inner surface 521 of the lamp-fixing unit 520 along a direction parallel to a diffusion plate 510 toward an inner area of the diffusion plate 510, a fourth protruding wall 5217 extending from an upper surface of the third protruding wall 5216 toward the diffusion plate 510 adjacent to the inner surface 521, the third protruding wall 5216 and the fourth protruding wall 5217 cooperatively defining a third reflective surface 5218 facing the diffusion plate 510. The inner surface 521, the second protruding wall 5213, and the fourth protruding wall 5216 cooperatively define a chamber 5219 to receive a light source 530.
Projectile paths of light rays from the light source 530 can be reflected by the second reflective surface 5214 and the third reflective surface 5218, the reflective surface 541 of the reflective plate 540, before finally projecting into the diffusion plate 510. It is to be understood that curvatures of the second reflective surface 5214, the third reflective surface 5218, and the reflective surface 541 of the reflective plate 540 may all be adjusted, so as to attain a preferred optical performance.
Referring to FIG. 7, a backlight module 600 in accordance with a fifth preferred embodiment is shown. The backlight module 600 is similar in principle to that of the third embodiment, except that the backlight module 600 further includes a reflector 680 defining a through hole (not labeled) conformed to a light source 630 therein. The reflector 680 is disposed on an inner surface of an aluminum based PCB 670, the light source 630 being exposed through the through hole thereof. It is to be understood that the reflector 680 may be directly connected with the inner surface of the lamp-fixing unit of the present backlight module.
Referring to FIG. 8, a backlight module 700 in accordance with a sixth preferred embodiment is shown. The backlight module 700 includes a diffusion plate 710, two lamp-fixing units 720, a plurality of light sources 730, a reflective plate 740, and a frame 780. The lamp-fixing units 720 are same as the lamp-fixing unit 520 of the preferred fourth embodiment. The light sources 730 are fixed on an inner surface of the lamp-fixing units 720 correspondingly. The frame 780 is same as the frame 280 of the first preferred embodiment, except that the frame 780 has only two sidewalls (not shown) extending from two opposing edges not aligned with the lamp-fixing units 720 of a base 781. Each lamp-fixing units 720 is aligned on either opposing edge that does not have a sidewall extending from the base 781, further connecting with the two sidewalls. The reflective plate 740 is a curved plate having a crest (not labeled) that has two opposing reflective surfaces 741. The reflective plate 740 is disposed on the base 781 with the two opposing reflective surfaces 741 facing the light sources 730 and the two lamp-fixing units 720. The diffusion plate 710 is positioned on the two lamp-fixing units 720. The reflective plate 740 can reflect light rays from the light sources 730 to the diffusion plate 710 uniformly.
It is to be understood that the light sources of the present direct type backlight module can also be cold cathode fluorescent lamps.
Finally, while the present invention has been described with reference to particular embodiments, the description is illustrative of the invention and is not to be construed as limiting the invention. Therefore, various modifications can be made to the embodiments by those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims.

Claims

1. A direct type backlight module comprising:

a diffusion plate;

at least a lamp-fixing unit disposed under one edge of the diffusion plate, the lamp-fixing unit having an inner surface facing the inner area underneath the diffusion plate, an outer surface opposite to the inner surface, and a plurality of fin structures defined on the outer surface;

at least a light source fixed on the inner surface of the lamp-fixing unit; and

a reflective plate disposed adjacent the lamp-fixing unit and under the diffusion plate, light rays emitted from the light source being uniformly reflected toward the diffusion plate by the reflective plate.

2. The direct type backlight module according to claim 1, wherein the inner surface of the lamp-fixing unit is slanted with respect to a horizontal portion of a reflective plate.

3. The direct type backlight module according to claim 2, wherein an inclination angle defined by the inner surface of the lamp-fixing unit with respect to the horizontal portion of the reflective plate is chosen to be in a range from about 30 degrees to about 150 degrees.

4. The direct type backlight module according to claim 1, wherein the lamp-fixing unit further comprises an upper reflective portion, the upper reflective portion having a first protruding wall extending from a top of an inner surface of the lamp-fixing unit along a direction parallel to the diffusion plate towards an inner area of the diffusion plate, a second protruding wall extending from a bottom surface of the first protruding wall toward the reflective plate adjacent to the inner surface, the first protruding wall and the second protruding wall cooperatively defining a second reflective surface facing the reflective plate.

5. The direct type backlight module according to claim 1, wherein the lamp-fixing unit further comprises an bottom reflective portion, the bottom reflective unit includes a third protruding wall extending from a bottom of an inner surface of the lamp-fixing unit along a direction parallel to the diffusion plate toward an inner area of the diffusion plate, a fourth protruding wall extending from an upper surface of the third protruding wall toward the diffusion plate adjacent to the inner surface, the third protruding wall and the fourth protruding wall cooperatively defining a third reflective surface facing the diffusion plate.

6. The direct type backlight module according to claim 1, further comprising a first heat conductive layer, sandwiched between the light source and the inner surface of the lamp-fixing unit.

7. The direct type backlight module according to claim 6, further comprising an aluminum based printed circuit board sandwiched between the light source and the first heat conductive layer.

8. The direct type backlight module according to claim 7, further comprising a second heat conductive layer sandwiched between the aluminum base printed circuit board and the light source.

9. The direct type backlight module according to claim 1, further comprising a reflector defining a through hole conformed to the light source therein, the reflector being disposed on the inner surface of lamp-fixing unit, and the light source being exposed through the through hole thereof.

10. The direct type backlight module according to claim 1, further comprising a frame, the frame having a rectangular base according to the diffusion plate, and three sidewalls extending perpendicularly from three edges excluding the edge aligned with the lamp-fixing unit of the base, the diffusion plate being positioned on a top of sidewalls.

11. The direct type backlight module according to claim 1, wherein the backlight module comprises two lamp-fixing units and a plurality of light sources fixed on an inner surface of each lamp-fixing unit, the two lamp-fixing units being disposed under two opposing edges of the diffusion plate respectively.

12. The direct type backlight module according to claim 11, wherein the reflective plate is a curved plate having a crest that has two opposing reflective surfaces, the reflective plate being disposed under the diffusion plate and between the two lamp-fixing units, the two opposing reflective surfaces of the reflective plate facing the two lamp-fixing units respectively.

13. The direct type backlight module according to claim 12, further comprising a frame, the frame having a rectangular base according to the diffusion plate, and only two sidewalls extending perpendicularly from two opposing edges not aligned with the lamp-fixing units of the base, the reflective plate being disposed on the base with the two opposing reflective surfaces facing the light sources and the two lamp-fixing units.

14. The direct type backlight module according to claim 1, wherein a material of the lamp-fixing unit is selected from a group comprising of aluminum, magnesium, copper or their alloys.

15. The direct type backlight module according to claim 1, wherein the light source is selected from a group comprising of light emitting diode and cold cathode fluorescent lamp.

16. A direct type backlight module comprising:

a diffusion plate being a substantially flat sheet having opposite two sides;

a reflective plate disposed at one side of the diffusion plate and spaced from the one side of the diffusion plate; and

a first light source disposed at the one side of diffusion plate and adjacent one edge of the diffusion plate, wherein the reflective plate has at least one reflective portion slanted toward the diffusion plate so that light rays emitted from the first light source is uniformly reflected toward the diffusion plate by the at least one reflective portion.

17. The direct type backlight module of claim 16, wherein the reflective plate is a smooth curved sheet bent towards the diffusion plate.

18. The direct type backlight module of claim 16 further comprising a second light source disposed at the one side of the diffusion plate and adjacent an opposite edge of the diffusion plate with the reflective plate located between the first and second light sources.

19. The direct type backlight module of claim 18, wherein the reflective plate is a curved plate having a crest that has two opposing reflective surfaces, the reflective plate being disposed under the diffusion plate and between the two light sources, the two opposing reflective surfaces of the reflective plate facing the two light sources respectively.

20. The direct type backlight module of claim 16, wherein the first light source comprising an inner surface facing the inner area underneath the diffusion plate, an outer surface opposite to the inner surface, and a plurality of fin structures defined on the outer surface.