Abstract:
A module for equalizing light in liquid crystal display, having a light source and at least one gapless microlens array, is described. The gapless microlens array has a substrate and a plurality of bumps located on the substrate, and the bumps are connected closely with each other so that there is no gap between the bumps. Light is gathered, equalized and diffused by using the gapless microlens array.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a back light module of a panel, and more particularly to a module for equalizing light.  
       BACKGROUND OF THE INVENTION  
       [0002]     User demand for entertainment equipment is particularly high as a result of the rapid development of multimedia applications. Conventionally, the cathode ray tube (CRT) display, which is a type of monitor, is commonly used. However, the cathode ray tube display does not meet the needs of multimedia technology because of the large volume thereof. Therefore, many flat panel display techniques such as liquid crystal display (LCD), plasma display panel (PDP), and field emission display (FED) have been recently developed. Of these techniques, the liquid crystal display (LCD) is attracting attention in the field of displays as a full-color display apparatus.  
         [0003]     The LCD (Liquid Crystal Display) is a planar display with low power consumption. In comparison with the CRT (Cathode Ray Tube) of the same screen size, the LCD is much smaller in its space occupation and weight. Unlike the curved screen in conventional CRTs, it has a planar display screen. With these advantages, LCDs have been widely used in various products, including palm calculators, electronic dictionaries, watches, mobile phones, notebook computers, communication terminals, display panels or even personal desktop computers.  
         [0004]     A conventional back light type LCD comprises a front-end liquid crystal panel and a back-end back light module. Therefore, a large back light module is required for providing enough illumination to pass through the liquid crystal layer to show the information of the LCD. Typically, fluorescent lamps are used as the back light source. The light passes through a back light film to provide uniform illumination of the liquid crystal panel.  
         [0005]      FIG. 1  illustrates a cross-sectional view of a conventional back light module. The main components of the back light module  10  comprise a light source  12 , a light guide  14 , a diffusion sheet  16  and a brightness enhancement film  18 . The operation method of the conventional back light module  10  is to use this light guide  14  to lead the light  12  to pass through the optical films to generate a uniform light. Typically, a lamp, light emitting diode (LED) or cold cathode fluorescent lamp (CCFL) can be used as the light  12  of the back light module  10 . Generally, a large-sized panel always uses a CCFL as the back light source because the CCFL has inherent advantages, such as a long life span and high illuminating efficiency. On the other hand, the LED is a suitable back light source for a small size panel.  
         [0006]     The light guide  14  is used to guide the light  12 . The brightness enhancement film  18  can be a prism made of a resin material. A sawtooth-shaped resin is formed over a substrate to generate a spotlighting efficiency. A 60% brightness efficiency can be increased by assembling the brightness enhancement film  18  in the back light module  12 . Moreover, a reflective plate  22  is assembled on the other side of the light  12 , which also can increase the brightness efficiency. Typically, a protective plate  20  is assembled on the top of the back light module  10  to protect the optical components thereof.  
         [0007]     There are two types of the back light module, edge-side type and direct type.  FIG. 1  illustrates the structure of the direct type back light module.  FIG. 2  illustrates the structure of the edge-side type back light module. The main difference between the two types of back light modules is that the light  12  is located on the side of the light guide  14  in the edge side type back light module. Typically, only one CCFL is located on the side of the edge side type back light module to serve as the light  12 . A V-shaped light guide  14  and a reflective plate  22  are used in this module to reflect the light uniformly into the module. Such structure can reduce the thickness of the back light module. Therefore, the structure is suitable for use in a notebook. However, it is difficult to get a uniform brightness in this structure. The light  12  is located on the bottom in the direct type back light module. This type of back light module uses at least two lamps and this structure provides a brighter light. The power consumption, however, is also increased. The thickness of the back light module is also increased. Therefore, this structure is suitable for a LCD monitor or a LCD television.  
       SUMMARY OF THE INVENTION  
       [0008]     According to the above descriptions, the conventional optical films in a back light module include a light guide, a diffusion sheet and a brightness enhancement film. This structure can cause a situation where the light is absorbed and reflected among these optical films, which degrades the brightness of the light.  
         [0009]     Therefore, the main object of the present invention is to provide a module for equalizing light in a liquid crystal display. A gapless microlens array is used to form a gapless microlens structure, which can get a better efficiency for collecting and equalizing light efficiency.  
         [0010]     Another object of the present invention is to provide a module for equalizing light in a liquid crystal display. A gapless microlens array replaces the conventional diffusion sheet or the brightness enhancement film.  
         [0011]     Accordingly, the uniform light module of the present invention comprises a light source and a gapless microlens array. The gapless microlens array is used to equalize the light. The array is composed of a substrate and a plurality of bulges located on the substrate. These bulges are connected together and there are no spaces between them.  
         [0012]     According to the preferred embodiment of the present invention, the gapless microlens array is formed of a macromolecular transparent material, such as Polyimide (PI), Polymethyl Methacrylate (PMMA) and Polycarbonate (PC). The top view of the bugle can be a hexagon, a square, a polygon or a combined structure. The gapless microlens array replaces the conventional diffusion sheet or brightness enhancement film. However, the diffusion sheet or the brightness enhancement film also can be assembled on the back light module of the present invention when necessary. Moreover, a prism or brightness-enhancing structure also can be assembled on the back light module to increase the light collection efficiency.  
         [0013]     The uniform light module reduces the components of the back light module. The energy degradation due to the absorption or reflection of the components can be reduced. Therefore, the brightness efficiency can be increased. Moreover, the ease of assembling this structure makes the back light module smaller and cheaper. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     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:  
         [0015]      FIG. 1  illustrates the structure of the direct-type back light module;  
         [0016]      FIG. 2  illustrates the structure of the edge side-type back light module;  
         [0017]      FIG. 3  illustrates a cross-sectional diagram of the gapless microlens array of the present invention;  
         [0018]      FIG. 4  illustrates a top view diagram of the gapless microlens array according to the first embodiment;  
         [0019]      FIG. 5  illustrates a top view diagram of the gapless microlens array according to the second embodiment;  
         [0020]      FIG. 6  illustrates a cross-sectional diagram of a three-dimensions gapless microstructure array model used to manufacture the gapless microlens array according to the preferred embodiment of the present invention; and  
         [0021]      FIG. 7  and  FIG. 8  respectively illustrates a schematic diagram of using the gapless microlens array in the back light module of a liquid crystal display according to the preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0022]     The present invention provides a uniform light module with one or more one gapless microlens array.  
         [0023]     Microlenses are widely used in the optical fiber, optical communication and optical electrical products. For example, a microlens is assembled in the end terminal of the optical fiber to collect light. However, some gaps exist between the microlens of the microlens array, which can affect the dots per inch.  
         [0024]     Therefore, the present invention uses a gapless microlens array to solve the above problem.  FIG. 3  illustrates a cross-sectional diagram of the gapless microlens array of the present invention. Referring to  FIG. 3 , the gapless microlens array  100  of the present invention comprises a substrate  102  and a plurality of bulges  104  located on the substrate  102 . These bulges are connected together. In other words, there are no spaces between these bulges.  
         [0025]     According to the preferred embodiment, the preferred cross-sectional view of the bulge  104  is a ball and similar lens structure. Therefore, light collection and equalization are improved. The top view of the bugle  104  can be a hexagon as shown in  FIG. 4  or a square as shown in  FIG. 5 . This is because a hexagon or a square structure can fit tightly between the bulges  104 . However, other structures can also be used in the present invention.  
         [0026]     For achieving mass production, micro injection forming technology, micro pressure forming technology or UV light forming technology are used in the present invention to form the gapless microlens array. The metal model used in the micro injection forming technology or micro pressure forming technology is a three-dimensions microstructure array model. This model is formed by an electroform or a discharge working technology.  FIG. 6  illustrates a cross-sectional diagram of a three-dimensions gapless microstructure array model used to manufacture the gapless microlens array according to the preferred embodiment of the present invention. The following paragraphs describe the manufacturing method.  
         [0027]     Referring to  FIG. 6 , the manufacturing method of the three-dimensions gapless microstructure array model  200  first adopts a spin coating technology to form buffer layer  204  over the substrate  202 . The material for forming the buffer layer  204  can be a Polyimide or a Polyamide. Next, a photoresist layer is formed over the buffer layer  204 . Then, a photolithography process is performed to pattern the photoresist layer. A thermal process is performed to heat the substrate  202  until the temperature of the photoresist material is higher than the glass transforming temperature. At this time, the photoresist material is melted to form the bumps  206  on the buffer layer  204 . The preferred photoresist material is a material with a glass-transforming temperature of about 100° C. to 350° C., such as Polymethyl Methacrylate. After that, a sputtering process is performed to form a conductive metal layer (not shown in the figure) over the bumps  206 . Next, another metal layer  208  is formed over the bumps  206 . This metal layer  208  is used to eliminate the spaces between the bumps  206 . The material for forming the conductive metal layer can be copper. The material for forming the metal layer  208  can be nickel. This method provides a more precise structure. After the three-dimensional gapless microstructure array model  200  is finished, manufacture of a gapless microlens array can start.  
         [0028]     The gapless microlens array of the present invention is manufactured by micro injection forming technology, micro pressure forming technology or UV light forming technology. According to the preferred embodiment of the present invention, the gapless microlens array can be formed from a macromolecular transparent material, such as the Polyimide (PI), Polymethyl Methacrylate (PMMA) and Polycarbonate (PC). The gapless microlens array of the present invention has a better light diffusion efficiency, which can uniformly diffuse the light. Moreover, the bulges can be used as the lens, which can improve the light collection efficiency. In other words, the gapless microlens array can replace the diffusion sheet or the brightness enhancement film in the conventional back light module. Moreover, the different appearances and the different curves of the bulges can provide brightness efficiency and scattering efficiency. The user can change the appearance or the curve ratio according to the requirement. Generally, when the distribution of the bulges is more highly concentrated, light collection and equalization is improved.  
         [0029]      FIG. 7  illustrates a schematic diagram of using the gapless microlens array in the back light module of a liquid crystal display according to the preferred embodiment of the present invention. Referring to  FIG. 7 , a light guide  304  is located over the light source  302  to lead the light into the back light module. However, in another embodiment, the light guide  304  can also be removed. A plurality of CCFL can be used to serve as the light source  302 . A reflective plate  300  is used to enhance the light. The gapless microlens array  100  of the present invention is assembled in the above of the light guide  304 . The gapless microlens array  100  can be assembled toward or away from the light guide  304  in the back light module. Moreover, a protective plate  306  is assembled in the top of the back light module to protect this module. In accordance with the preferred embodiment, the gapless microlens array  100  can concentrate the light  302  led by the light guide  304  between positive and negative about 17 degrees that the liquid crystal display can accept.  
         [0030]     On the other hand, a plurality of gapless microlens arrays  100  also can be used in the back light module. Moreover, the gapless microlens arrays  100  can also be used with a conventional diffusion sheet, a brightness enhancement film or prism for different optical products. When a diffusion sheet is assembled into the back light module, the location of this diffusion sheet is over the gapless microlens arrays  100  of the  FIG. 7 . In other words, the location is between the protective plate  306  and the gapless microlens arrays  100 . When a brightness enhancement film is assembled into the back light module, the location of this brightness enhancement film is under the gapless microlens arrays  100  of the  FIG. 7 . In other words, the location is between the light guide  304  and the gapless microlens arrays  100 . Generally, the brightness enhancement film is a prism or a cylinder structure. The principle of the brightness enhancement film is well known in the art, and is not further explained here.  
         [0031]     On the other hand, the substrate for forming the gapless microlens array can not only form the bulges on one side but also form the other structure on the other side. Referring to  FIG. 8 , bulges  404  are formed on one side of the substrate  402  and the other microstructure  406  are formed on the other side of the substrate  402 . The microstructure can be the gapless structure as described above to improve the brightness. Moreover, the material of the substrate  402  can be the material forming the light guide for simplifying the components in the back light module. On the other hand, a diffusion sheet  408  also can be assembled into the back light module as shown in the  FIG. 8   
         [0032]     The uniform light module with gapless microlens array of the present invention can reduce the components required in the module. Therefore, the volume of the back light module can be reduced. Moreover, the energy degradation due to the absorption or reflection of the components can be reduced. Therefore, the brightness efficiency can be increased. Moreover, the ease of assembling easily assembling can help the back light module to reduce volume and cost.  
         [0033]     As is understood by a person skilled in the art, the foregoing preferred embodiments of the present invention are illustrative of the present invention rather than limiting of the present invention. It is intended that this description cover various modifications and similar arrangements included within the spirit and scope of the appended claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structure.