This application claims the priority benefit of Taiwan application serial no. 97126669, filed on Jul. 14, 2008. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of specification.
1. Field of the Invention
The present invention relates to a back light module, in particular, to a back light module with a desirable light-output effect.
2. Description of Related Art
With the rapid development of the semiconductor and relevant electronic industry, digital tools such as mobile phones, digital cameras, digital video cameras, notebook computers, and desk-top computers all develop towards the trend of convenience, multifunction, and desirable appearance. However, when these information products are used, display screens are indispensable man-machine communication interfaces. The display screens of the above products can bring more convenience for users' operations. Furthermore, liquid crystal displays have become the mainstream of display screens. Since the liquid crystal display does not possess a light-emitting function, a back light module must be provided below the liquid crystal display for providing a light source, so as to achieve the displaying function.
Accordingly, the present invention is directed to a back light module, which is suitable for solving the problem of a poor light-output effect of a conventional back light module.
A back light module is provided in the present invention, which includes a light-guiding plate and a point light source. The light-guiding plate has a first light emitting surface and a light receiving surface adjacent to the first light emitting surface. The point light source has a package housing, and the package housing is tightly bonded with the light receiving surface of the light-guiding plate to form a welding interface. The light-guiding plate may includes one or multiple diffusion structures (not shown) corresponding to the point light source for diffusing an incident light near the light receiving surface; however, the diffusion structures are not the features of the invention so that they would not be discuss in the invention.
In an embodiment of the present invention, the above package housing is made of Acrylonitrile-Butadiene-Styrene resin (ABS).
In an embodiment of the present invention, the above light-guiding plate is made of polycarbonate (PC) or acrylic.
In an embodiment of the present invention, the above back light module further includes a supporting substrate. The point light source is disposed on the supporting substrate. In an embodiment, the above point light source has a second light emitting surface and a bottom surface adjacent to the second light emitting surface. The bottom surface is connected to the supporting substrate, and the second light emitting surface is connected to the light receiving surface. In this case, the supporting substrate is, for example, a flexible circuit board. In other embodiments, the second light emitting surface and the bottom surface are opposite to each other. In addition, the bottom surface is connected to the supporting substrate, and the second light emitting surface is connected to the light receiving surface. The supporting substrate is, for example, a printed circuit board (PCB).
In an embodiment of the present invention, the above back light module further includes a frame. The point light source and the light-guiding plate are snapped into the frame.
In an embodiment of the present invention, the above point light source is, for example, a light-emitting diode (LED).
In an embodiment of the present invention, the above package housing is tightly bonded with the light receiving surface of the light-guiding plate through ultrasonic welding.
In the present invention, since the point light source is tightly bonded with the light-guiding plate, no gap is formed between the point light source and the light-guiding plate. When the back light module of the present invention is turned on, light emitted from the point light source can completely enter the light-guiding plate, thus enhancing the light utilization rate of the back light module. Moreover, no light leakage occurs between the point light source and the light-guiding plate of the present invention, which enables the back light module to have a desirable light-output effect.
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.
The light-guiding plate 220 has a first light emitting surface 222 and a light receiving surface 224 adjacent to the first light emitting surface 222. The plurality of point light sources 230 is tightly bonded to the light receiving surface 224 of the light-guiding plate. The point light sources 230 are, for example, a plurality of light-emitting diodes (LEDs), and are disposed on the supporting substrate 240.
If the point light sources 230 are not tightly bonded to the light-guiding plate 220 (that is, as the design of the back light module 100), a portion of light emitted from the point light sources 230 directly enters the light-guiding plate 220, but the other portion of the light is directly emitted out or absorbed by other elements. The portion of the light that is directly emitted out may be concentrated in a particular direction to form a beam, since they are not subjected to the effect of the light-guiding plate 220. In addition, the portion of the light that is directly emitted out may also form a halo due to the interference with other light. Both the unnecessary beam and halo are main factors that cause the deterioration of the light-output quality of the back light module 100.
Therefore, in this embodiment, the point light sources 230 are tightly bonded to the light-guiding plate 220, such that the light emitted from the point light sources 230 can only be emitted out via the light-guiding plate 220. That is, the light sources provided by the back light module 200 are not easily interfered by other light and thus have desirable quality. Besides, the structure with the point light sources 230 being tightly bonded to the light-guiding plate 220 is also helpful for improving the light utilization rate of the back light module 200.
Since the point light sources 230 in this embodiment are LEDs, each of the point light sources 230 has, for example, a package housing 236. When the back light module 200 is manufactured, in order to avoid an unnecessary gap formed between the point light sources 230 and the light-guiding plate 220 due to errors in the positioning process, the point light sources 230 and the light-guiding plate 220 can be bonded together through ultrasonic welding. The ultrasonic welding herein refers to a bonding process in which two objects in contact with each other are partially melted at the contact surface there-between due to frictional heats generated through high-frequency (like ultrasonic frequency, over 20,000 Hz) micro-amplitude vibrations. The two objects are bonded together upon curing of the melted portion.
Since the point light sources 230 and the light-guiding plate 220 are bonded to each other through ultrasonic welding in this embodiment, the back light module 200 further includes a plurality of welding interfaces 250 between the point light sources 230 and the light-guiding plate 220, so as to enable the point light sources 230 to be tightly bonded to the light-guiding plate 220. On one hand, through ultrasonic welding, the point light sources 230 and the light-guiding plate 220 can be tightly bonded with each other. On the other hand, in terms of the cost of the manufacturing process, the two members can be tightly bonded to each other through ultrasonic welding, without using other adhesives or glues, which is further helpful for reducing the cost required for purchasing the bonding materials. Moreover, in the steps of the ultrasonic welding process, the frictional heats are merely generated close to the contact surface between the two objects, and do not melt other portions of the point light sources 230 or the light-guiding plate 220. Therefore, the point light sources 230 and the light-guiding plate 220 will not be damaged during the ultrasonic welding process, which is helpful for maintaining the yield of the manufacturing process of the back light module 200.
In fact, the ultrasonic welding process is preferably used to bond two materials with similar or same properties. In the back light module 200, the package housing 236 is, for example, made of Acrylonitrile-Butadiene-Styrene resin (ABS), and the light-guiding plate 220 is, for example, made of polycarbonate (PC) or acrylic. For example, the arcrylic material may be polymethyl methacrylate (PMMA). Since the above two materials have similar properties, the light-guiding plate 220 and the point light sources 230 can be tightly bonded together through ultrasonic welding. Moreover, the welding interfaces 250 are formed after the two melted materials are cured, so that the welding interfaces 250 are, for example, made of a mixed material of ABS and PC or a mixed material of PMMA and ABS. It should be understood that, the material of the package housing 236 and the light-guiding plate 220 are not limited to the above materials in the present invention. In other embodiments, the package housing 236 and the light-guiding plate 220 may also be made of other materials in a similar or the same manner. In other words, the welding interfaces 250 may be made of other mixed materials.
Since the light-guiding plate 220 and the point light sources 230 are tightly bonded to each other through ultrasonic welding in this embodiment, the light emitted from the point light sources 230 do not leak out, which enables the back light module 200 to have a desirable light-output effect.
To sum up, in the back light module of the present invention, the light-guiding plate and the point light sources are tightly bonded together, such that the light leakage via the gap between the point light sources and the light-guiding plate can be eliminated. In particular, the tight bonding between the light-guiding plate and the point light sources can prevent the light emitted from the point light sources from being directly emitted out of the back light module, which improves the light-output effect of the back light module. Moreover, the back light module of the present invention can more effectively utilize the light emitted from the point light sources and thus have a better performance.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.
Number | Date | Country | Kind |
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97126669 | Jul 2008 | TW | national |