Abstract:
A LED backlight module including a diffusion plate, at least an optical devices, at least a light-emitting diode and a second reflection surface is provided. The optical device is provided underneath the diffusion plate and has a first reflection surface. The light-emitting diode is provided underneath the optical device, for emitting light to the first reflection surface where first reflection of the light is performed. The second reflection surface is provided underneath the light-emitting diode, for receiving the light of the first reflection and performing second reflection of the received light. By controlling light paths of LED with the optical devices, light emitted from LED may be leaded to a specific direction instead of directly emitting from a front surface of LED, so as to achieve the performance of color-mixing and uniform distribution.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to backlight modules, and more particularly, to a backlight module using a light-emitting diode (LED) as a light source.  
       BACKGROUND OF THE INVENTION  
       [0002]     The amount of liquid crystal display televisions (LCD TVs) is reportedly estimated to achieve at a level of at least 16.24 millions in 2006 due to a strong demand of LCD TVs in the future (Display Search). There is therefore another commercial chance generated for raw materials and devices in LCD key component industries, and among them a backlight module is especially one of the important developing elements. In accordance with environmental protections and a trend of using a compact backlight source in a backlight module, a cold cathode fluorescent lamp (CCFL) is going to be gradually replaced by a light-emitting diode (LED) and the characteristic of a light source is changed from a line source such as a CCFL to a point source such as a LED.  
         [0003]     Therefore, in the development of next generation backlight sources, the characteristics of “high resolution”, “high luminescence”, “mercury-free”, “high color reproducibility” provided by a backlight module using a LED light source can raise an additional value to a liquid crystal display instead of merely giving an impression of “space-saving” of conventional LED. Thereby, it is generally believed that the applications of a LED backlight module can be extended to portable electronic products from now on, and can be spread rapidly into various industry fields such as automobiles, commercial light boxes, displays, video mediums such as TV, information, communications, household electronics, consumers and the like. Meanwhile, present biggest challenge encountered in using LED as a backlight source is how to uniformly diffuse the light of a point-source, single-color LED to the entire surface and obtain uniform color and luminance. Related technical patents include U.S. Pat. No. 5,499,120 and U.S. Patent Publication No. 2005/0001537.  
         [0004]     According to U.S. Pat. No. 5,499,120, LEDs with broad light angle are arranged into a matrix to serve as a backlight of LCD. However, since the LEDs of such backlight module are arranged regularly and do not have any optical devices for controlling light paths of LEDs, it is not able to perform a color-mixing process. Thus, the technique is applied only to singe-color light sources and would not obtain a colorizing effect.  
         [0005]     Furthermore, U.S. Patent Publication No. 2005/0001537 proposes a technique for applying total internal reflection (TIR) theory to LED. A specific optical device structure that satisfies TIR angle is used to direct the light emitted from LED chips of different colors to emit from a side surface thereof, so as to achieve color-mixing and uniform distribution.  
         [0006]     However, the optical device structure used in this patent must satisfy the threshold angle requirement of the TIR theory, which is extremely complicated in designing. Furthermore, the optical device structure can only afford a small tolerance. Therefore, complicated tooling structures should be needed, which leads to the difficulty in production and increases costs due to a requirement of using a plurality of tooling molds for production.  
         [0007]     Moreover, it is real hard to satisfy the requirement of the TIR theory. Once the position of the LED chip is misaligned with the corresponding position of the TIR surface, light would emit from the front surface. Therefore, products manufactured by substantially executing this technique cannot completely direct light to emit from a side surface, which leads to non-uniform emitting light.  
         [0008]     Furthermore, since a small portion of light will emit from the front surface of the LED using the structure of this technique, two diffusion plates should be provided in the entire module in order to improve the uniformity of emitting light. And an additional small spot reflector should be added on the top surface of LED for complete shielding and satisfying the threshold angle requirement of TIR. That is, a structure of stacking a lot of layers should be employed to improve the uniformity problem of emitting light in the foresaid patent. Therefore, the LED backlight module using the technique of this patent has problems of complicated structure, manufacturing difficulty, and high costs, which is disadvantageous to industry application and needs further improvements.  
         [0009]     Besides, typical package structures of LEDs include a sink type and an overhead type (protrudent type) LED package structure, which generate different output light angles according to different package structures. For example, in an overhead type LED package structure, light generated by the LED will be directly emitted from a region within 180 degrees. Thus, the optical devices provided over the LED chip should only reflect the light outputted from the front of the LED chip. On the contrary, in a sinking type LED package structure, since primary output regions are shielded, the light generated by the LED chip will be deflected to generate special output light angles. However, the special optical devices used in the foresaid patent only provide specific refraction angles, which are not able to satisfy both the sinking type and the overhead type LED package structures and have no applicability in multiple purposes.  
         [0010]     Since the above conventional technology having problems of not able to achieve colorizing, having non-uniform output light, having complicated structures, difficult to be manufactured, having higher cost, and not having industrial applicability, it is thus an urgent task to provide a simple and easily producible structure and a lower cost to enhance color-mixing property and uniformity of a backlight module, so as to increase the industrial applicability and solve the problems generated by conventional technology.  
       SUMMARY OF THE INVENTION  
       [0011]     In view of the above defects of conventional technology, a primary objective of the present invention is to provide a LED backlight module to enhance the performance of color-mixing and uniform distribution.  
         [0012]     Another objective of the present invention is to provide a LED backlight module having a simple and easily producible structure.  
         [0013]     Yet another objective of the present invention is to provide a LED backlight module that may reduce manufacturing cost.  
         [0014]     Another objective of the present invention is to provide a LED backlight module that may increase the industrial applicability.  
         [0015]     To achieve the above objectives, the present invention provides a LED backlight module, wherein the LED backlight module includes a diffusion plate, one or more optical devices, one or more light-emitting diodes, and a reflection sheet. The diffusion plate is used to uniformly diffuse light. Each of the optical devices is provided underneath the diffusion plate and has a reflection surface of high reflectivity. Each of the light-emitting diodes is provided underneath each of the optical devices. The reflection sheet is provided underneath the light-emitting diodes and on a side surface of the entire module.  
         [0016]     Preferably, each of the optical devices has a structure produced by a material of high transmittance, wherein the material of high transmittance is a material selected from plastic or glass. The reflection surface of each of the optical devices can be a layer selected from a metal layer or a dielectric layer, wherein the metal layer can be a structure obtained by a treatment such as an evaporation treatment or a sputtering treatment, and the dielectric layer can be a structure obtained by stacking multiple layers of dielectric materials. In a preferred embodiment, the metal layer is a structure formed by sputtering silver or aluminum and the like on the reflection surface of each of the optical devices produced by plastic and the like. In another preferred embodiment, the dielectric layer can be a structure formed by stacking TiO 2  and the like on the reflection surface of each of the optical devices produced by glass and the like. In another preferred embodiment, the side surface of each of the optical devices can be a slanted surface, wherein an included angle between the slanted surface and the normal direction of the output light of light-emitting diode ranges from 1 degree to 45 degrees.  
         [0017]     Moreover, the reflection surface has a geometrical cross-section, wherein the reflection surface can be selected from a group consisting of V-shape, curve, circle, ellipse, and sawtooth cross-section. Preferably, the included angle between the reflection surface of V-shape cross-section and the light-emitting diode ranges from 1 degree to 60 degrees. Furthermore, the LED backlight module of the present invention can include a plurality of optical devices and corresponding light-emitting diodes, and the light-emitting diodes can be a random permutation of red, green, and blue LEDs. In a preferred embodiment, the light-emitting diodes can be white light-emitting diodes.  
         [0018]     Besides, the LED backlight module can further include a brightness enhancement film (BEF) provided on the diffusion plate, wherein the brightness enhancement film is preferably a film or sheet produced by a material selected from polyester or polycarbonate so as to concentrate light and enhance brightness.  
         [0019]     The present invention provides a direct-lit LED backlight module, wherein LEDs of multiple colors including red, blue, green and the like are arranged underneath the liquid crystal display; the bottom and side reflection sheet of the backlight module can reflect light into the liquid crystal display; and every LED includes an optical device that can control light paths of LED. Thus, since the reflection surface of each of the optical devices has high reflectivity, light directly emitted from LED chips can be leaded to a specific direction instead of directly emitting from the front surface. In this way, the defect of not able to achieve color-mixing with single-color light sources in the conventional technology can be eliminated. And without the problem of improving emitting light uniformity by a structure stacking a lot of layers in the conventional technology, the backlight module may thus obtain the performance of color-mixing and uniform distribution.  
         [0020]     Therefore, the optical devices used in the present invention have simple and easily producible structure, which can solve the problems of difficult to be manufactured, high cost, and disadvantageous to industrial applicability in the conventional technology using the complicated structure and the structure stacking multiple layers. Thereby, the present invention does not generate the problem of difficult to be manufactured in the conventional technology, which can lower the cost and applied broadly to a lot of industries.  
         [0021]     Therefore, the present invention achieves color-mixing and uniform distribution by providing a LED backlight module that is simple and easily producible, lower cost, and able to enhance industrial applicability, so as to solve all kinds of problems generated in the conventional technology. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     The present invention can be more fully understood by reading the following detailed description of the preferred embodiments, with reference made to the accompanying drawings, wherein:  
         [0023]      FIG. 1  is a structural schematic diagram showing an LED backlight module according to a first embodiment of the present invention;  
         [0024]      FIG. 2  is a structural schematic diagram showing an optical device according to the first embodiment of the present invention;  
         [0025]      FIG. 3  is a structural schematic diagram showing the LED arrangement according to the first embodiment of the present invention;  
         [0026]      FIG. 4  is a structural schematic diagram showing an optical device in an LED backlight module according to a second embodiment of the present invention;  
         [0027]      FIG. 5A  is a structural schematic diagram showing an optical device in an LED backlight module according to a third embodiment of the present. invention;  
         [0028]      FIG. 5B  is a light distribution diagram of the optical device according to the third embodiment of the present invention;  
         [0029]      FIG. 6A  is a structural schematic diagram showing the optical device according to the first embodiment of the present invention in a sinking type LED package structure; and  
         [0030]      FIG. 6B  is a light distribution diagram of the optical device according to the first embodiment of the present invention in the sinking type LED package structure. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]     The following preferred embodiments are provided to further illustrate the present invention, and are by no means used to limit the scope of the invention.  
         [0032]     First Embodiment  
         [0033]     FIGS.  1  to  3  are schematic diagrams depicting a light-emitting diode backlight module according to a first embodiment of the present invention. As shown in  FIG. 1 , the backlight module  1  includes a diffusion plate  11 , a plurality of optical devices  13 , a plurality of light-emitting diodes  15 , and a reflection sheet  17 .  
         [0034]     The diffusion plate  11  is provided underneath a liquid crystal display  12  to scatter and uniform diffusion of light. Wherein the liquid crystal display  12  has a conventional structure and operating mechanism that it will not be explained any further.  
         [0035]     Each of the optical devices  13  is individually provided underneath the diffusion sheet  11 , and preferably has a structure produced by a high transmitting material selected from plastic, glass or other suitable materials. Furthermore, as shown in  FIG. 2 , each of the optical devices  13  has a reflection surface  131  of high reflectivity. Wherein, each reflection surface  131  of the optical devices  13  has a layer of metal layer, dielectric layer, or other equivalent layers of mirror, and the included angle between the reflection surface  131  and each of the light-emitting diodes  15  ranges from 1 degree to 60 degrees. Wherein the metal layer can be a structure obtained by a treatment such as an evaporation treatment or a sputtering treatment, for example, the metal layer can be produced by sputtering silver or aluminum on the reflection surface  131  of each of the optical devices  13  formed by plastic and the like; the dielectric layer is a structure formed by stacking multiple layers of dielectric materials, for example, the dielectric layer can be formed by stacking TiO 2  on the reflection surface  131  of each of the optical devices  13  produced by glass and the like. It is not necessary to address that the treatment and material required for turning the reflection surface  131  into a mirror surface can be varied depending on requirements and are not limited in the disclosure of the embodiment.  
         [0036]     Each of the light-emitting diodes  15  is individually provided underneath each of the optical devices  13 . As shown in  FIG. 3 , each of the light-emitting diodes  15  has a random permutation of red (R), green (G), and blue (B) LEDs staggered arranging under the liquid crystal display. In this way, each of the light-emitting diodes  15  has one of the optical devices  13  to control light paths of LED wherein each of the optical devices  13  has a reflection surface  131  of high reflectivity to reflect light directly emitting from each of the light-emitting diodes  15  to a specific direction instead of emitting from the front surface. It is generally known by a person with general knowledge in the technical field and there is no need to address that the light-emitting diodes  15  can be selected from white light-emitting diodes.  
         [0037]     The reflection sheet  17  is provided underneath each of the light-emitting diodes  15  and on the side edge of the entire module to reflect light emitted from each of the light-emitting diodes  15  into the liquid crystal display  12  again and increase the efficiency of light usage. It has to be understood that the diffusion plate  11  and the reflection sheet  17  are general to a person having general knowledge in the technical field and would not be explained any more.  
         [0038]     In this embodiment, the LED backlight module  1  can further include a brightness enhancement film (BEF)  19  provided on the diffusion plate  11  to concentrate light and enhance brightness. The brightness enhancement film  19  can be, but not be limited to, a film or sheet produced by materials such as polyester or polycarbonate. Meanwhile, in other embodiments, the brightness enhancement film  19  can be integrated into the liquid crystal display  12  to lower the cost and simplify the structure. However, the modification can be easily devised and achieved by a person having general knowledge in the technical field that it is not going to be further explained here.  
         [0039]     Since each of the optical devices has a reflection surface  131 , light emitted from each of the light-emitting diodes  15  would contact different positions of the reflection surface  131 . By means of the characteristic of high reflectivity resulted from reflecting light toward each direction to the bottom, it is able to obtain an anisotropic effect of uniform light dispersion. In this way, after being reflected by the optical devices  12 , light emitted from each of the light-emitting diodes  15  would be reflected into the liquid crystal display  12  through the reflection sheet  17 , and the diffusion plate  17  can shield few upward (i.e. toward the front surface) emitting light so as to achieve color-mixing and uniform effects.  
         [0040]     Comparing to conventional technology using optical devices of special structures and using multiple modules for processing such that it is difficult to fulfill due to the high cost, the optical devices of the present invention merely use a substrate such as an extruded substrate and thus the processing thereof is easy. Moreover, the LED backlight module using the present invention doesn&#39;t have to satisfy the crucial condition of total internal reflection (TIR) in the conventional technology, the problem of failing to completely direct light to emit from the side surface of a product produced by substantially executing the conventional technology can be solved.  
         [0041]     Therefore, the LED backlight module using the present invention can achieve color-mixing and uniform effects such that not only the manufacturing cost thereof is lower than the conventional technology but the easy process thereof without defects in the conventional technology, the industrial applicability may be further enhanced.  
         [0042]     Second Embodiment  
         [0043]      FIG. 4  is a schematic diagram depicting a light-emitting diode backlight module according to a second embodiment of the present invention. To further explain the present invention to be easily understood, the same or similar devices of the first embodiment are denoted with the same or similar symbolic references and skip further drawings and illustrations.  
         [0044]     As shown in  FIG. 4 , the difference between the first embodiment and the second embodiment lies in that each of the optical devices  13  of the first embodiment have a reflection surface  131  of a V-shaped cross-section; while each of the optical devices  13 ′ of the first embodiment have a reflection surface  131 ′ of a curved cross-section.  
         [0045]     In this embodiment, the reflection surface  131 ′ of a curved cross-section can further decrease light dispersed from the front surface so as to enhance the uniformity of light diffusion.  
         [0046]     Certainly, the cross-sectional shape of the reflection surface  131  and  131 ′ are not limited to disclosed hereinabove V-shape and curve. Any geometric or non-geometric designs that are easy to be released may apply to the present invention, for example, circle, ellipse, sawtooth, or other polygon and the like which the curvature between two curved surfaces of the reflection surface can be different from each other and determined by desired light dispersion angles. In other words, the hereinabove disclosures such as amount and positions of LED, shapes of the reflection surface and materials and processes of coating are merely exemplary illustrations and should not be limited to the above embodiments. It has to be noted that equivalent embodiments can be easily revised by a person with general knowledge in the technical field.  
         [0047]     Third Embodiment  
         [0048]      FIG. 5A  is a schematic diagram depicting an LED backlight module according to a third embodiment of the present invention. To further explain the present invention to be easily understood, the same or similar devices of the first embodiment are denoted with the same or similar symbolic references and detailed drawings and illustrations are omitted.  
         [0049]     As shown in  FIG. 5A , the difference between the first embodiment and the third embodiment lies in that each of the optical devices  13  of the first embodiment has a reflection surface  131  of a V-shaped cross-section; except for a reflection surface  131  of a V-shaped cross-section (or a curved cross-section), each of the optical devices  13 ″ of the third embodiment has a side surface formed with a slanted surface  133  and is provided, for instance, over a sinking type LED package structure  151 .  
         [0050]     In this embodiment, since the sinking type LED package structure  151  is used, a portion of regions surrounding each of the light-emitting diodes  15  is shielded, and generates special angles of output light by shielding the light generated by each of the light-emitting diodes  15 . Moreover, the light of small refraction angle is refracted to the reflection surface  131  through the slanted surface  133  provided on the side surface of each of the optical devices  13 ″, and subsequently refracted to a specific angle through the reflection surface  131 , so as to achieve broadened output light angles. Therefore, each of the optical devices  13 ″ of the embodiment can be applied to both the sinking type and the overhead type LED package structure. Besides, since the output light angles can be broadened, the space between each of the optical devices  13 ″ and the diffusion plate can be further reduced to reduce the thickness of the entire LED backlight module.  
         [0051]     Since each of the optical devices  13 ″ can be made of materials of high reflectivity such as plastic, glass, or other suitable materials, at a direction close to normal direction most of the incident light can be transmitted through the slanted surface  133 ; adversely, the incident light that is distant from the normal direction will be refracted to the reflection surface  131 . The slanted angle of the slanted surface  133  is preferably controlled within a range that the extending direction of the light generated by each of the light-emitting diodes  15  can overlap with the slanted surface. More preferably, an included angle between the slanted surface and the normal direction of the output light of each of the light-emitting diodes  15  ranges from 1 degree to 45 degrees.  
         [0052]     Comparative Example  
         [0053]     Referring to  FIGS. 5A, 5B ,  6 A, and  6 B, the output light angle and intensity of the optical devices  13  of the first embodiment and the optical devices  13 ″ of the third embodiment are compared. The test is performed with the same conditions.  
         [0054]     As shown in  FIGS. 5A and 6A , each of the optical devices  13  and  13 ″ are provided over the sinking type LED package structure, wherein both each of the optical devices  13  and  13 ″ have the same included angle between the reflection surface  131  and each of the light-emitting diodes  15 . Comparing to each of the optical devices  13 , each of the optical devices  13 ″ is further provided with a slanted side surface  133 .  
         [0055]     As shown in  FIGS. 5B and 6B , wherein the horizontal axis stands for output light angle and the vertical axis stands for output light intensity, the output light angle of each of the optical devices  13  is primarily concentrated at about  106  degrees and a small portion at about 11 degrees. The output light angle of each of the optical devices  13 ″ is primarily concentrated at about 75 degrees, and the output light of small angle is gradually decreased. Therefore, according to the test results, the present invention can effectively decrease the light outputted from the front surface.  
         [0056]     Therefore, the LED backlight module of the present invention can solve defects of conventional technology by not only via optical devices control light paths to direct light emitted directly from LED chips to a specific direction instead of direct emit from the front surface such that achieve color-mixing and uniform effects; but also save production cost and enhance industrial applicability.  
         [0057]     The embodiments described hereinabove are merely provided to exemplary illustrate the characteristic and utility of the present invention, and are not used for limiting the scope of substantial technical content of the present invention. The scope of substantial technical content of the present invention should be generally defined as the following claims, and any technical embbodiments or methods which is totally the same or is an equivalent modification of that defined in the following claims by anyone should be considered as containing in the claims.