Patent Application
20080285277
The present invention relates to backlight module, more particularly, to a bottom lighting type backlight module for use in, for example, a liquid crystal display (LCD).
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 module can be classified into an edge lighting type or a bottom lighting type based upon the location of lamps within the device. The edge lighting type backlight module has a lamp unit arranged at a side portion of a light guiding plate for guiding light. The edge lighting type backlight modules are commonly employed in small-sized LCD due to their lightweight, small size, and low electric consumption. However, the edge lighting type backlight modules are not suitable for large-sized LCD (20 inches or more). A bottom lighting type backlight module has a plurality of lamps arranged in regular positions to directly illuminate an entire surface of an LCD panel. The bottom lighting type backlight modules have higher efficiency of light usage and longer operational lifetime than the edge lighting type backlight modules, the bottom lighting 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
The optical sheets 33 are layered on a top of the sidewalls of the frame 31 facing the base 321. The light emitting diodes 34 are aligned on an upper surface of the base of the heat dissipation panel 32 facing the optical sheets 33. The reflecting unit 35 defines a plurality of holes (not labeled) therein according to the light emitting diodes 34. The reflecting unit 35 is disposed on the base 321 of the heat dissipation panel 32. The reflecting unit 35 further defines a plurality of holes exposing the light emitting diodes 34 to emit light rays to enter the optical sheets 33 through the holes thereof. The base 321 of the heat dissipation panel 32 is usually formed of materials with a high heat conductive coefficient. This is because the base 321 is in direct contact with the light emitting diodes 34, a great deal of heat produced by the light emitting diodes 34 can be directly dissipated out through the base 321 and the fins 322.
As described the components of the backlight module 30 are plentiful, thus assembling the backlight module is complicated and difficult. In addition, the thickness of the backlight module 30 is limited due to the physical properties of the heat dissipation panel 32. Furthermore, the heat dissipation panel 32 commonly needs an auxiliary device such as a fan, to increase its heat dissipation efficiency. If, however, an air-cooling fan is used, dust is whirled up to adhere to the surface of light emitting diodes 33 or to the optical sheets 33 disposed thereon, thus deteriorating the uniformity of brightness of the backlight module 30. Furthermore, a noise produced by the fan is also a shortcoming.
What is needed, therefore, is a bottom lighting type backlight module that overcome the above mentioned shortcomings.
A bottom lighting type backlight module according to a preferred embodiment includes a frame, a plurality of light sources, a reflecting sheet and at least one optical sheet. The frame includes a base and a plurality of sidewalls extending from the peripheral of the base to define an opening. The base defines a plurality of first guide holes, and a plurality of fins extending out from an outer surface of the base. The each optical sheet is disposed on the opening of the frame. The at least one optical sheet and the frame collectively defines a chamber. The reflecting sheet is disposed in the frame, for partitioning the chamber into an illumination space and a heat dissipation space, above and below the reflective sheet respectively. The heat dissipation space is an open space in communication with an exterior of the frame via the first guide holes, for introducing cooling air supplied from outside to diffuse heat accumulated therein. The reflecting sheet defines a plurality of through holes. The light sources are arranged on the base of the frame under the reflecting sheet corresponding to the through holes, illuminating light through the through holes towards the at least one optical sheet.
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.
Many aspects of the present bottom lighting 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 bottom lighting type backlight module. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
Reference will now be made to the drawings to describe preferred embodiments of the present bottom lighting type backlight module, in detail.
Referring to
The three optical sheets 14 include a light diffusion plate 141, a prism sheet 142, and a bright enhancement film 143 are stacked on the opening 119 of the frame 11 in that order. Referring to
Each light emitting diode 12 includes a substrate 124 and a light luminescent top portion 122 disposed on the substrate. When the light luminescent top portion 122 emits light, the substrate 124 generates heat. The substrate 124 of each light emitting diode 12 is attached to the base 111 of the frame 11 by a plurality of screws 123 in the heat dissipation space 16B. The light luminescent top portion 122 of each light emitting diode 12 passes through the through holes 131 of the reflecting sheet 13 and exposes in the illumination space 16A, thus radiating light toward the optical sheets 14 directly.
In this embodiment, the backlight module 10 may further include four reflecting sidewalls 132 extending from the periphery of the reflecting sheet 13. Tops of the four reflecting sidewalls 132 are in contact with the optical sheets 14. The reflecting sidewalls 132 are used for reflecting light back to the optical sheets 14 to improve a light energy utilization rate. The frame 11 may be formed of materials with a high heat conductive coefficient such as metal or engineering plastic. The metal may be preferably selected from copper or aluminum.
In this embodiment, the backlight module 10 may further include an upper frame 15 for fixing the three optical sheets 14 tightly. The upper frame 15 includes an upper base 151 and four upper sidewalls 153 extending perpendicularly from the upper base 151 correspondingly. The upper base 151 defines an opening 154 in the interior thereof and forms four frame edges 156. The optical sheets 14 are exposed through the opening 154 of the upper base 151. Each upper sidewalls 153 of the upper frame 15 and the second sidewalls 113 of the main frame 41 correspondingly define a plurality of locking elements (not labeled) thereon, thus the upper frame 15 and the frame 11 could be assembled together thereat to fix the three optical sheets 14 tightly.
As described above, in the present embodiment, the closed illumination space 16A is formed between the optical sheets 14 and the reflecting sheet 13 installed in the chamber 16, the light luminescent top portions 122 of light emitting diodes 12 are housed therein. The open heat dissipation space 16B is formed between the reflecting sheet 13 and the base 111 of the frame 11. Furthermore, it is impossible that dust and dirt fed in together with the cooling air that enters the illumination space 16A, thus preventing dust and dirt from adhering the optical sheets 14. In addition, because the light emitting diodes 12 are in contact with the base 111 of the heat dissipation space 16B, the heat generated from the light emitting diodes 12 is substantially accumulated within the heat dissipation space 16B. Therefore, a shape of the optical sheets 13 may not be easily deformed due to the temperature change. Furthermore, cooling air may be forcibly fed through the first guide holes 114 and the second guide holes 118 by an external air-cooling fan (not shown) or the like. Since the cooling air moves along the surfaces of light emitting diodes 12 and the base 111 of the frame 11, it becomes possible to diffuse the heat generated from the light emitting diodes 12 outward very efficiently. The fins 115 of the base 111 and the first sidewalls 112 could also help to improve the backlight module 10's heat dissipation capabilities.
In alternative embodiments, the present backlight module may further include a receiving frame and a transparent supporting plate. The receiving frame includes a frame body, a rim portion extending from a bottom of the frame body running perpendicularly around an inside of the receiving frame. The receiving frame may be fixed at the top of the frame, the rim portion thereof being used to receiving the optical sheets. The transparent supporting plate defines a plurality of holes therein corresponding to the through holes of the reflecting sheet. The supporting plate may be fixed on the protrusions of the second sidewalls of the frame, being used to support the reflecting sheet.
It is to be understood that the present backlight module not only may employ a combination of the optical sheets, but also may employ one optical sheet, such as a light diffusion sheet used for uniformly diffusing the light emitted from the light source.
It should be pointed out that the structure of sidewalls of the present frame is not limited to the illustrated embodiment. The present frame may be integrally manufactured, the first sidewalls and second sidewalls thereof extending from the peripheral of the base to define an opening, should be considered to be within the scope of the present invention.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 94139712 | Nov 2005 | TW | national |
The present application is a continuation application of U.S. application Ser. No. 11/501,941 filed on Aug. 10, 2006, which claims priority from Taiwan Patent Applications No. 94139712 filed on Nov. 11, 2005, the entire contents of which are incorporated herein by reference for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11501941 | Aug 2006 | US |
| Child | 12220380 | US |
