Abstract:
An optical film assembly comprises a plurality of optical films and a merging region. The optical films can be chosen arbitrarily and are superposed layer by layer. The merging region is formed by hot pressing and merging the optical films together so as to integrate them into an optical film assembly which is advantageous to the fabrication process of the backlight module. Also, a method and an apparatus for manufacturing the optical film assembly are also provided to produce the optical film assembly.

Description:
[0001]    This application is a Divisional of co-pending Application Ser. No. 11/473,264 filed on Jun. 23, 2006, which claims priority to Application No. 94121267 filed in Taiwan, on Jun. 24, 2005. The entire contents of all of the above applications are hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to an optical film assembly, and more particularly to the optical film assembly that can be integrated by a plurality of optical films. 
         [0004]    2. Description of the Prior Art 
         [0005]    Among the image displaying apparatuses, a liquid crystal display (LCD) has the following advantages: light weight, small volume, lower power consumption, and no radiation, and that is why it can be applied widely to various equipments. 
         [0006]    The LCD can be mainly divided into two parts. The first part is a backlight module for providing stable and even light. The second part is a liquid crystal panel having two substrates and a liquid crystal layer hold between the substrates. The liquid crystal panel is located in the light projectile place of the backlight module. By controlling the orientation of liquid crystal molecules to change the ways of light in the liquid crystal panel, the diverse regions in the liquid crystal panel can show various brightness or colors to achieve versatile image displaying. For the light of the liquid crystal panel is adopted from the backlight module, so the features of the LCD such as brightness, even intensity, contrast, and available visual angle . . . etc would be greatly affected by the backlight module. 
         [0007]    Therefore, in order to make the light of backlight module diffuse evenly, the backlight module adapts and cooperates multilayer optical films including the diffusion sheets and the prism sheets to produce a better light distribution and heighten the quality display. 
         [0008]    Please refer to  FIG. 1 , an exploded view of a typical backlight module. As shown, the backlight module comprises a reflector  10 , a frame  11 , a light guide plate  12 , a plurality of optical films  13 , and a light source (not shown in the figure) disposed relevantly according to the light projecting ways. 
         [0009]    The combination of the frame  11  and the reflector  10  form a box shape to bear the light guide plate  12 , a plurality of the optical films  13 , and other components of the backlight module. 
         [0010]    The light guide plate  12  is disposed inside of the frame  11  on the top of the reflector  10 . The light source (not shown here) can be disposed in a lateral side or a bottom side of the light guide plate  12 . Light of the light source projects onto the light guide plate  12  and can be guided by the light guide plate  12 . A lower portion of light can also be transmitted onto the light guide plate  12  by the reflecting of the reflector  10 . 
         [0011]    Each of the optical films  13  can be selected as different types depending on the demand of designs. For example, as shown in  FIG. 1 , the optical films  13  comprise a diffusion sheet  131 , a first prism sheet  132 , and a second prism sheet  133 . 
         [0012]    The diffusion sheet  131  is disposed above the light guide plate  12  so that the light projected from the light guide plate  12  can be diffused evenly by the diffusion sheet  131 . 
         [0013]    The first prism sheet  132  is disposed above the diffusion sheet  131 . By utilizing an injection molding process or sticking an acrylic resin on the first prism sheet  132 , the first prism sheet  132  can have a saw-toothed surface that can re-concentrate the light which has already proliferated so as to reduce the loss of light and increase the brightness of the backlight module. 
         [0014]    The second prism sheet  133  is disposed above the first prism sheet  132  to present a function similar to that of the first prism sheet  132 . The focusing direction of the second prism sheet  133  is perpendicular and interlaced with the focusing direction of the first prism sheet  132 . 
         [0015]    The above-mentioned optical films can help backlight module to provide a brighter light. 
         [0016]    In the process of assembling the backlight module, the frame  11  and the reflector  10  are assembled together first, and then the light guide plate  12  and the light source are put in. After that, the optical films  13  is layered onto the light guide plate  12  or into the frame  11  one by one. If any errors happens in the assembly process, the optical films  13  would become warped or have interference patterns that highly degrade the quality of image displaying. 
         [0017]    Furthermore, if any of the optical films  13  has different properties on opposing sides. It is quite possible to disposed them with wrong facing without consciousness. 
         [0018]    Therefore, the process of assembling the backlight module needs a lot of labor and time, and so is low efficiency. 
         [0019]    Besides, each aforesaid optical film  13  needs to be cut for many times so as to get the needful size. Such a manufacturing mode may also increase the cost in time and labor. 
         [0020]    Therefore, how to increase the efficiency of assembling the optical films and lower the cost in manufacturing are objects for people whom are familiar with this art to dedicate. 
       SUMMARY OF THE INVENTION 
       [0021]    One object of the present invention is to provide an optical film assembly which is made up by plurality of optical films to reduce assembly procedures. 
         [0022]    A further object of the present invention is also to provide a manufacturing method for the present optical film which just needs to be cut for once, and thereby the optical film assembly composed of numerous optical films from a reduced assembly scheme can be obtained. 
         [0023]    One more object of the present invention is to provide a manufacturing apparatus for the present optical film. 
         [0024]    The optical film assembly in accordance with the present invention includes a plurality of optical films and a merging region. Each of the optical films is superposed layer by layer and the merging region is formed by hot pressing the optical films. 
         [0025]    The present invention also discloses a manufacturing method of manufacturing the optical film assembly. The method includes the following steps: 
         [0026]    Superposing a plurality of optical films; 
         [0027]    Hot pressing part of the optical films so as to make the optical films adhered to each other; and 
         [0028]    Cutting the optical films 
         [0029]    The present invention also discloses an apparatus which can adapt to partially adhere a first optical film to a second optical film. The apparatus includes a cutting platform, a first roller, a second roller, and a thermal cutter. 
         [0030]    The cutting platform can be an arbitrary platform which is used to bear weight while in cutting the first optical film and the second optical film. 
         [0031]    The first roller can transmit the first optical film along a first path who passes through the cutting platform. 
         [0032]    The second roller can transmit the second optical film along a second path who passes through the cutting platform and overlaps the first path. 
         [0033]    The thermal cutter, located above the cutting platform, can move vertically for cutting the first optical film and the second optical film to a predetermined shape. 
         [0034]    Therefore, while in cutting the first optical film and the second optical film, this thermal cutter can heat and bond the cut optical films simultaneously. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]    Other features and advantages of this invention will become more apparent in the following detailed description of the preferred embodiments of this invention, with reference to the accompanying drawings, in which: 
           [0036]      FIG. 1  shows an exploded view of a typical backlight module; 
           [0037]      FIG. 2  shows a perspective view of an embodiment of an optical film assembly according to the present invention; 
           [0038]      FIG. 3  shows an exploded view of a backlight module where the optical film assembly is applied in according to the present invention; 
           [0039]      FIG. 4  shows a flow chart of an embodiment of the manufacturing method according to the present invention; and 
           [0040]      FIG. 5  shows a perspective view of an embodiment of the manufacturing apparatus according to the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0041]    Please refer to  FIG. 2 , a perspective view of an embodiment of an optical film assembly  20  according to the present invention. As shown in  FIG. 2 , the optical film assembly  20  can include a plurality of optical films similar to that described in the background section. 
         [0042]    The optical films of the present invention can be any type. For example, the optical films can be selected from the group consisting of diffusion sheet and brightness enhancement film (such as prism sheet). In this embodiment, as shown in  FIG. 2 , the optical films include a lower diffusion sheet  201 , a first prism sheet  202 , a second prism  203 , and an upper diffusion sheet  204 . Besides, each of the optical films is superposed layer by layer. 
         [0043]    The first prism sheet  202  is superposed above the lower diffusion sheet  201 . The first prism sheet  202  has a saw-toothed surface that makes the proliferated light re-concentrated again so as to reduce the loss of light and increase the brightness of the backlight module. 
         [0044]    The second prism sheet  203  is superposed above the first prism sheet  202  and has a function similar to that of the first prism sheet  202 . The focusing direction of the second prism sheet  203  is perpendicular to and interlaced with the focusing direction of the first prism sheet  202 . 
         [0045]    The upper diffusion sheet  204  is superposed above the second prism sheet  203 . The light projected from the second prism sheet  203  can be diffused evenly by the upper diffusion sheet  204 . 
         [0046]    Besides, the optical film assembly according to the present invention further includes a merging region  205 . The merging region is formed by heating, pressing, or hot pressing the optical films so as to make the optical films adhered to each other. Thus, the optical films  201 , 202 , 203 , 204  can be integrated into an independent optical film assembly  20  and thus can be fabricated in a backlight module directly non-like the prior art which needs to be assembled one by one and therefore spends a lot of labor and time. Above description means that the adjacent optical films  201 , 202 , 203 , 204  can be adhered temporarily or permanently after heating, pressing, or hot pressing the optical films  201 , 202 , 203 , 204  so as to fix the relative positions of the optical films  201 , 202 , 203 , 204  temporarily or permanently. In a preferred embodiment, the optical films  201 , 202 , 203 , 204  are heated up around the Glass Transition Temperature so as to have stickiness on a plurality of surfaces of the optical films  201 , 202 , 203 , 204  for making the adjacent optical films  201 , 202 , 203 , 204  adhered each other temporarily or permanently. 
         [0047]    It should be noticed that the location and the shape of the merging region  205  can be varied depending on the demands of the designs. 
         [0048]    For example, the merging region  205  can locate in corner of the optical film assembly  20 . In another word, the optical films of the optical film assembly  20  are hot pressed only in their respective corners. Moreover, the merging region  205  also can locate at an edge of the optical film assembly  20 . Similarly, the merging region  205  also can locate at the periphery of the optical film assembly  20 . In addition, the merging region  205  can comprise a-line or a dot or any other shapes. 
         [0049]    Please refer to  FIG. 3 , an exploded view of a backlight module where the optical film assembly  20  is applied in according to the present invention . As shown, the backlight module includes a reflector  21 , a frame  22 , a light guide plate  23 , an optical film assembly  20 , and a light source (not shown in the figure) which is properly disposed according to the light projecting ways. 
         [0050]    The combination of the frame  22  and the reflector  21  form as a box shape which can bear the light guide plate  23 , the optical film assembly  20 , and other components of the backlight module. 
         [0051]    The light guide plate  23  is disposed inside of the frame  22 , on top of the reflector  21 , and a light source (not shown) can be disposed in its lateral side or bottom side. Light of the light source projecting onto the light guide plate  23  can be guided by the light guide plate  23 . A bottom part of light can be transmitted onto the light guide plate  23  again by the reflecting of the reflector  21 . 
         [0052]    The optical film assembly  20  can be fabricated in the backlight module directly on top of the light guide plate  23  so as to reduce the consuming of manpower and working-hours in assembling. 
         [0053]    The present invention also discloses a manufacturing method for manufacturing the optical film assembly  20  shown in  FIG. 2 . Please refer to  FIG. 4  which shows a flow chart of an embodiment of the manufacturing method according to the present invention. The manufacturing method includes the following steps: 
         [0054]    Si: Superpose a plurality of optical films. These optical films are selected from the group consisting of diffusion sheet and brightness enhancement film (such as prism sheet). They are layer-wise superposed in order according to respective property of the optical films. 
         [0055]    S 2 : Hot press part of the optical films so as to make the optical films adhered to each other. In this step, to heat and thus soften a predetermined area of the optical films is carried out so as to make the predetermined area of the optical films hot press and adhered mutually to form a hot pressed part of the optical films. The way of heating and hot pressing the predetermined areas of the optical films directly can avoid using various types of glue or fixing agents so as to prevent from the residual materials sticking on the optical films that would definitely affect the quality of the optical films. 
         [0056]    S 3 : Cut the optical films. 
         [0057]    In a preferred embodiment, the steps of hot pressing and cutting the optical films are performed simultaneously so as to reduce the manufacturing procedures. In another word, to heat the predetermined area of these optical films can be performed simultaneously with the cutting. 
         [0058]    Further, the step of hot pressing the predetermined area of the optical films to form a hot pressed part of the optical films can be performed by cutting the optical films, such as heat cutting or laser cutting. Taking the heat cutting for an example, a cutting tool is provided with enough temperature to hot press and adhere the optical films, so that the optical films can be cut and hot press to form a hot pressed part of the optical films simultaneously 
         [0059]    While in cutting these optical films to a needful size, the predetermined areas of these optical films are hot pressed and a hot pressed part of the optical films is formed among the optical films to integrate these optical films into an optical film assembly as shown in  FIG. 2 . Above description means that the adjacent optical films can be adhered temporarily or permanently after heating, pressing, or hot pressing the optical films so as to fix the relative positions of the optical films temporarily or permanently. In a preferred embodiment, the optical films are heated up around the Glass Transition Temperature so as to have stickiness on a plurality of surfaces of the optical films for making the adjacent optical films adhered each other temporarily or permanently. 
         [0060]    Similarly, location and shape of the hot pressed part of the optical films can be dependent on the demands of the designs, such as the hot pressed part of the optical films in the corner, at the edge, or the periphery of the optical film assembly. In addition, the hot pressed part of the optical films can comprise a line, a dot, or any other shape. 
         [0061]    The present invention also discloses a manufacturing apparatus for manufacturing the optical film assembly  20  as shown in  FIG. 2  in accordance with the method shown in  FIG. 4 . 
         [0062]    Please refer to  FIG. 5 , a perspective view of an embodiment of the manufacturing apparatus according to the present invention is shown. The manufacturing apparatus, adapted to partially adhere a first optical film  30  to a second optical film  31  includes a cutting platform  32 , a first roller  33 , a second roller  34 , and a thermal cutter  35 . 
         [0063]    The cutting platform  32  can be an arbitrary platform used to bear weight while cutting the first optical film  30  and the second optical film  31 . 
         [0064]    The first roller  33  is used to load the first optical film  30 . As shown, the first optical film  30  can be coiled around the first roller  33 . 
         [0065]    The first roller  33  transmits the first optical film  30  along a first path  331  above the cutting platform  32 . 
         [0066]    The second roller  34  is used to load the second optical film  31 . As shown, the second optical film  31  can be coiled around the second roller  34 . The second roller  34  transmits the second optical film  31  along a second path  341  above the cutting platform  32  and overlaps the first path  331 . The intersecting angle between the first path  331  and the second path  341  depends on the demands. For example, if the first optical film  30  is a prism sheet and the second optical film  31  is also a prism sheet, the intersecting angle can be ninety degrees so as to make perpendicular the focusing directions of these two films. 
         [0067]    The thermal cutter  35  is on the top of the cutting platform  32  which can move vertically for cutting the first optical film  30  and the second optical film  31  to a predetermined shape. Therefore, while the thermal cutter  35  cuts the first optical film  30  and the second  31  optical films, this thermal cutter  35  heats and cuts the optical films substantially at the same time, and makes the sections near the cut to be adhered mutually. 
         [0068]    In a preferred embodiment, the manufacturing apparatus further includes a fixer  36 . In addition, shape of the thermal cutter  35  can be formed as a hollow frame. The thermal cutter  35  can cut the first optical film  30  and the second optical film  31  to a predetermined shape. The location of the fixer  36  can be on top of the cutting platform  32  and inside the thermal cutter  35 . 
         [0069]    Before the thermal cutter proceeds to cut, the fixer  36  can move lower in advance to fix the first optical film  30  and the second optical film  31  on the cutting platform  32  by pressing in order to avoid the first optical film  30  and the second optical film  31  being warped. 
         [0070]    After the thermal cutter  35  adheres and cuts the first optical film  30  and the second optical film  31  to form an optical film assembly, the optical film assembly and the thermal cutter  35  can be separated by pushing from the fixer  36 . 
         [0071]      FIG. 5  illustrates an example of a manufacturing apparatus which are applied to two pieces of optical films. If more than two pieces of optical films is involved to be cut simultaneously, a set of roller can be added. For example, in the case that three pieces of optical films are to be cut and hot pressed simultaneously, the manufacturing apparatus can have a third roller for transmitting a third optical film along a third path on the platform. The arrangement of the intersecting angles between the first path, the second path, and the third path can depend on the properties of the third optical film, the second optical film, and the first optical film. 
         [0072]    Besides, in another embodiment, all the optical films to be cut can be properly loaded to the same roller. 
         [0073]    In summary, the optical film assembly according to the present invention can be not only assembled into the backlight module directly but also can reduce the consuming of labor as well as time. Furthermore, the integrated films can provide a better structure strength to avoid possible single-layer warping while in being placed into the backlight module. Besides, because the optical film assembly is thicker than a typical single optical film, the optical film assembly is more convenient for robots to handle and thus the manufacturing automation can be feasible. 
         [0074]    Also, the optical film assembly can be made by the above-mentioned method and the above-mentioned apparatus. By providing the present invention, the optical films are cut, hot pressed and adhered simultaneously in a single step to get the optical film assembly with the needful size and shape, which the assembly having plural films can be easily placed into the backlight module at a time. Upon such an arrangement, the procedures of cutting as well as the alignment process during manufacturing can be greatly simplified. 
         [0075]    The embodiment above is to illustrate the invention in detail but not to give a specific embodiment. Any modification that doesn&#39;t exceed the essence of the invention should belong to this invention. Thus the invention should be safeguarded according to the claims as follows.