Abstract:
A planer light source device includes: a light source; alight source supporting member configured to support the light source and having a first face and a second face that is opposite to the first face; alight guide plate having a side face opposed to the first face of the light source supporting member and a light emitting face for emitting light from the light source; a metal frame configured to support the light guide plate; and a resin frame disposed to be overlaid on the second face of the light source supporting member. The resin frame includes a connection part for connecting with the metal frame within a plate thickness of the metal frame.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2006-320592, filed on Nov. 28, 2006, the entire contents of which are incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]      1 . Field of the Invention 
         [0003]    The present invention relates to a planer light source device using a light source. 
         [0004]    2. Description of the Related Art 
         [0005]    A planer light source device, for example, a planer light source device of a non-emissive display device such as a liquid crystal display, has a side light type (also called an edge light type) and a direct type. The planer light source device of the side light type has a light source disposed on the side face of a rear frame, whereas the planer light source device of the direct type has a light source disposed on the rear face of the rear frame opposed to a display part. 
         [0006]    Also, the planer light source device of the side light type includes a light guide plate for guiding the light from the light source in a desired direction, in which the light emitted from the light source including a linear light source such as a Cold Cathode Fluorescent Lamp (hereinafter referred to as CCFL) or a point light source such as a Light Emitting Diode (hereinafter referred to as LED) is reflected within the light guide plate and diffused with a diffusion pattern provided within the light guide plate to direct the light at a display screen. 
         [0007]    Further, a middle frame is disposed for sandwiching the light guide plate with the rear frame. A display panel is provided on the screen side of the light guide plate. A front frame that supports the display panel, the middle frame and the rear frame and has an opening is disposed on the screen side of the display panel. 
         [0008]    In the planer light source device, a step portion is provided on the side face of the middle frame, and a claw portion provided on the rear frame is fitted into the step portion of the middle frame to fix the middle frame and the rear frame together. 
         [0009]    Also, in the planer light source device (e.g., see JP-A-2002-40394), a window is provided in an engagement piece of a back face frame in contact with the side face of an intermediate frame, and engaged by a projection provided in the intermediate frame to fix the intermediate frame and the back face frame. 
         [0010]    However, it is required to provide the step portion or projection on the side face of the middle frame, so that the thickness of the side face of the middle frame is increased. Also, since the side face of the middle frame and the side face of the rear frame overlap, the planer light source device has a wider frame area (wider peripheral area of the frame of the display screen). 
         [0011]    Further, the peripheral portion of the light source is heated to high temperature due to heat generated from the light source, which cases the emission light flux of the light source to be lower and results in a problem that the light source is degraded in the life and reliability. Thus, there is a demand that the contact area between a lamp reflector and the rear frame is increased, whereby it is difficult to provide a fixing structure of the middle frame and the rear frame, which results in a problem that a movement occurs due to vibration or shock. 
         [0012]    Also, in JP-A-2002-40394, since the projection provided in the intermediate frame is not overlaid on the side face of a reflective sheet, the positional regulation of the reflective sheet could not be made when the planer light source device is assembled from the intermediate frame. 
       SUMMARY OF THE INVENTION 
       [0013]    This invention has been achieved in the light of the above-mentioned problems, and it is an object of the invention to provide a planer light source device using a light source with a narrow frame, which is superior in the assembling ability and the vibration and shock resistance without increasing the manufacturing processes. 
         [0014]    According to an aspect of the invention, there is provided a planer light source device includes: a light source; a light source supporting member configured to support the light source and having a first face and a second face that is opposite to the first face; a light guide plate having a side face opposed to the first face of the light source supporting member and a light emitting face for emitting light from the light source; a metal frame configured to support the light guide plate; and a resin frame disposed to be overlaid on the second face of the light source supporting member. The resin frame includes a connection part for connecting with the metal frame within a plate thickness of the metal frame. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is an exploded perspective view of a planer light source device according to an embodiment 1 of the present invention; 
           [0016]      FIGS. 2A and 2B  are views for explaining a connection part between a middle frame and a rear frame according to the embodiment 1 of the invention; 
           [0017]      FIG. 3  is a front view for explaining a convex part of the middle frame according to the embodiment 1 of the invention; 
           [0018]      FIG. 4  is a front view for explaining a concave part of the rear frame according to the embodiment 1 of the invention; 
           [0019]      FIG. 5  is a view for explaining another connection part between the middle frame and the rear frame according to the embodiment 1 of the invention; 
           [0020]      FIGS. 6A and 6B  are views for explaining a connection part between the middle frame and the rear frame according to an embodiment 2 of the invention; 
           [0021]      FIGS. 7A and 7B  are views for explaining a method for fitting the rear frame and the front frame according to the embodiment 2 of the invention; and 
           [0022]      FIG. 8  is a view for explaining another method for connecting the middle frame and the rear frame according to the embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    The preferred embodiments of the invention will be described below. The following explanation is intended for explaining the embodiments of the invention, but the invention is not limited to the following embodiments. To clarify the explanation, the following explanation may be appropriately omitted or simplified. Also, it is apparent to those skilled in the art that the components of the following embodiments may be easily changed, added or replaced within the scope of the invention. 
       Embodiment 1 
       [0024]      FIG. 1  is an exploded perspective view of a planer light source device according to an embodiment 1 of the invention.  FIG. 2A  is a view for explaining a connection part between a middle frame  7  and a rear frame  8  according to the embodiment 1 of the invention and  FIG. 2B  is a cross-sectional view of  FIG. 2A , taken along the line A-A.  FIG. 3  is a front view for explaining a convex part  7   c  of the middle frame  7  according to the embodiment 1 of the invention.  FIG. 4  is a front view for explaining a concave part  8   b  of the rear frame  8  according to the embodiment 1 of the invention.  FIG. 5  is a view for explaining another connection part between the middle frame  7  and the rear frame  8  according to the embodiment 1 of the invention. 
         [0025]    In  FIGS. 1 to 5 , a light source  2  such as a cold cathode fluorescent lamp (CCFL) covered with a lamp reflector  1  that is a light source supporting member is disposed near a side face  3   a  of a light guide plate  3 . The light from the light source  2  is incident on the side face  3   a  of the light guide plate  3 , and emitted from a light emitting face  3   b  of the light guide plate  3  (herein, the light emitting face means an upper surface of the light guide plate  3  as seen in the drawing). The optical sheets  5  such as a diffusion sheet for diffusing the light from the light source  2  and illuminating the display panel  4  uniformly, and a lens sheet for changing the angle of light from the light source  1  and increasing the brightness on a display screen  4   a  of a display panel  4  in the front direction are provided on the light emitting face  3   b  of the light guide plate  3 , and a reflective sheet  6  for effectively reflecting the light from the light source  1  to the light emitting face  3   b  of the light guide plate  3  is provided on a counter light emitting face  3   c  of the light guide plate  3  (herein, the counter light emitting face means a lower surface of the light guide plate  3  as seen in the drawing). 
         [0026]    The lamp reflector  1 , the light source  2 , the light guide plate  3 , the optical sheets  5  and the reflective sheet  6  are sandwiched between the middle frame  7  made of resin and the rear frame  8  made of metal. The middle frame  7  is provided with an opening  7   a , which corresponds to the light emitting face  3   b  of the light guide plate  3 . The light emitted from the light emitting face  3   b  of the light guide plate  3  emanates through the opening  7   a  of the middle frame  7 . 
         [0027]    Further, the lamp reflector  1 , the light source  2 , the light guide plate  3 , the display panel  4 , the optical sheets  5 , the reflective sheet  6 , the middle frame  7  and the rear frame  8  are supported by a front frame  9  having an opening  9   a.    
         [0028]    Though the lamp reflector  1  and the light source  2  are provided on only one side face  3   a  of the light guide plate  3  in  FIG. 1 , the invention is not limited to this configuration, but the light source and a light source board may be provided on two or more side faces of the light guide plate. Further, the light source  1  may be a point light source such as an LED or a laser diode (Laser Diode), in which if the point light source is employed, it is mounted and disposed on the light source board. 
         [0029]    Also, the light guide plate  3  is made of resin such as polyethylene terephthalate (PET), acrylic (such as PMMA: polymethyl methacrylate), polycarbonate (PC) or cycloolefin, or glass. Further, a light scattering portion (not shown) for disordering the light propagation direction to guide the light to the light emitting face  3   b  is formed on the counter light emitting face  3   c  of the light guide plate  3 . This light scattering portion functions as means for taking the light out of the light guide plate  3  by disordering the total reflection condition of light propagating within the light guide plate. More specifically, the means for scattering may be a method for printing the dot pattern on the counter light emitting face  3   c  of the light guide plate  3 , a method for roughening the counter light emitting face  3   c , or a method for forming the counter light emitting face  3   c  with irregularities such as micro spheres or prisms for changing the propagation direction of light. 
         [0030]    Also, the optical sheets  5  have the lens sheet sandwiched between the diffusion sheets, for example. Also, to increase the brightness of the display panel  4 , a plurality of lens sheets may be combined in consideration of the direction of prisms formed on the surface of the lens sheet. Also, the diffusion sheet may be a combination of two or more sheets to improve the diffusivity. It is preferable to optimize the use of the optical sheets  5  in view of the required brightness or flux distribution characteristic. 
         [0031]    Further, the reflective sheet  6  may be made of a material of polypropylene (PP) or polyethylene terephthalate (PET) mixed with barium sulfate or titanium oxide, a material of resin formed with minute bubbles, a material of metal plate on which silver is deposited, or a material of metal plate coated with paint containing titanium oxide. 
         [0032]    As shown in  FIGS. 1 to 4 , in this embodiment, a side face  7   b  of the middle frame  7  made of resin such as polycarbonate (PC) or acrylonitrile/butadiene/styrene (ABS) has a convex part  7   c  connected with a concave part  8   b  formed on a side face  8   a  of the rear frame  8  containing a metal frame made of aluminum, stainless or iron within the plate thickness t of the rear frame  8  on the opposite face  1   b  of the side face  1   a  of the lamp reflector  1  opposed to the side face  3   a  of the light guide plate  3 . With this convex part  7   c , when the planer light source device is assembled in the order of the optical sheets  5 , the light guide plate  3 , the reflective sheet  6 , the lamp reflector  1  and the rear frame  8  by turning the middle frame  7  upside down, the positional regulation for disposing the lamp reflector  1  is facilitated. 
         [0033]    Since the side face  8   a  of the rear frame  8  is contact with the face  1   b  of the lamp reflector  1 , it has a function of conducting the heat of the lamp reflector  1  that is heated to high temperature due to heat generated from the light source  2  to the rear frame  8  and dissipating the heat to the surroundings. Particularly, if an aluminum housing having high thermal conductivity is employed for the rear frame  8 , the heat from the light source  2  can be diffused efficiently to decrease the temperature of the light source  2 . 
         [0034]    Also, since it is unnecessary to provide a step portion or projection having the plate thickness or more on the side face  7   b  of the middle frame  7 , the thickness of the side face  7   b  of the middle frame  7  can be suppressed within the plate thickness. Therefore, the structure of the middle frame  7  is simplified, whereby the thickness and weight can be reduced. Further, since the side face  7   b  of the middle frame  7  and the side face  8   a  of the rear frame  8  are connected within the plate thickness of the rear frame  8 , the planer light source device can have a narrower frame at the periphery of the display screen. 
         [0035]    As shown in  FIG. 3 , the convex part  7   c  of the middle frame  7  and the concave part  8   b  formed on the side face  8   a  of the rear frame  8  can be easily fitted together by forming a notch  7   e  on the convex part  7   c  of the middle frame  7  to reach a top face  7   d  of the convex part  7   c.    
         [0036]    As shown in  FIGS. 3 and 4 , a projection part  7   f  overlaid on the opposite face  1   b  of the side face  1   a  of the lamp reflector  1  opposed to the side face  3   a  of the light guide plate  3  is formed in the convex part  7   c  of the middle frame  7 , and a lock part  8   c  engaged by the projection part  7   f  is formed within the plate thickness t of the rear frame  8  at the position corresponding to the projection part  7   f  of the middle frame  7  in the concave part  8   b  formed on the side face  8   a  of the rear frame  8 . Thereby, the middle frame  7  and the rear frame  8  can be fixed more tightly. When a vibration or shock is applied from the outside, it is possible to regulate the movement of the lamp reflector  1 , the light source  2 , the light guide plate  3 , the optical sheets  5  and the reflective sheet  6 . 
         [0037]    Assuming that the height of the notch  7   e  from the top face  7   d  of the convex part  7   c  in the middle frame  7  is h, and the height of the convex part  7   c  having convex-like shape in the middle frame  7  is H, as the value of H-h (which is the deference between the height H of the convex part  7   c  and the height h of the notch  7   e ) is smaller, the convex part  7   c  having convex-like shape in the middle frame  7  and the concave part  8   b  formed on the side face  8   a  in the rear frame  8  can be fitted together more easily. As the value of H-h is larger, the middle frame  7  and the rear frame  8  can be fixed more tightly. 
         [0038]    Next, assuming that the width of the projection part  7   f  in the middle frame  7  is w as shown in  FIGS. 3 and 4 , as the value of w is larger, the engagement strength of the projection part  7   f  of the middle frame  7  with the lock part  8   c  of the rear frame  8  is increased. Also, assuming that the width of the lock part  8   c  in the rear frame  8  is v, v≧w is particularly preferable to fix the projection part  7   f  in the middle frame  7  and the lock part  8   c  in the rear frame  8  securely. 
         [0039]    Also, though in this embodiment, the projection part  7   f  formed in the convex part  7   c  of the middle frame  7  is formed on both sides of the notch  7   e , the projection part  7   f  may be formed on only one side, and fixed with the lock part  8   c  in the rear frame  8 , as shown in  FIG. 5 . Since the other configurations and effects are analogous, the explanation thereof is omitted. 
       Embodiment 2 
       [0040]    Referring to  FIGS. 6 and 7 , an embodiment 2 of the invention will be described below. In this embodiment, the configurations of the lamp reflector  1 , the light source  2 , the light guide plate  3 , the display panel  4 , the optical sheets  5 , the reflective sheet  6 , and the middle frame  7  is the same as in the embodiment 1, wherein the same reference numerals are attached to those parts, and the explanation thereof is omitted. In the following explanation, the shape of the rear frame  8  and the front frame  9  will be particularly described with reference to  FIGS. 6 and 7 . Herein, the same reference numerals are attached to the same parts as in  FIGS. 1 to 5 . 
         [0041]      FIG. 6A  is a view for explaining a connection part between the middle frame  7  and the rear frame  8  according to the embodiment 2 of the invention, and  FIG. 6B  is a cross-sectional view of  FIG. 6A , taken along the line B-B.  FIG. 7A  is a view for explaining a method for fitting the rear frame  8  and the front frame  9  according to the embodiment 2 of the invention, and  FIG. 7B  is a cross-sectional view of  FIG. 7A , taken along the line C-C. 
         [0042]    In  FIGS. 6 and 7 , a bridge part  8   d  contacted with the convex part  7   c  of the middle frame  7  is formed in the concave part  8   b  formed on the side face  8   a  of the rear frame  8 , and has a shape overhanging in the opposite direction to the light source  2  in the plate thickness direction. Further, the front frame  9  that supports the lamp reflector  1 , the light source  2 , the light guide plate  3 , the display panel  4 , the optical sheets  5 , the reflective sheet  6 , the middle frame  7  and the rear frame  8  is provided with a hole  9   c  at a position of the side face  9   b  overlaid on the side face  8   a  of the rear frame  8 , the position corresponding to the bridge part  8   d  formed in the rear frame  8 . Also, the bridge part  8   d  of the rear frame  8  and the hole  9   c  of the frame  9  can be fitted together within the plate thickness of the frame  9 . Also, the hole  9   c  may be a notch. A method for connecting the convex part  7   c  of the middle frame  7  and the concave part  8   b  of the rear frame  8  is the same as in the embodiment 1. 
         [0043]    With this constitution, even when a vibration or shock is applied from the outside in the Y direction as shown in  FIG. 1 , the fitting of the convex part  7   c  of the middle frame  7  and the concave part  8   b  of the rear frame  8  can be securely kept from being released. Further, since it is unnecessary to provide the rear frame  8  and the front frame  9  with a fitting structure, the structure of the rear frame  8  and the front frame  9  can be simplified. 
         [0044]    Since the plate thickness of the bridge part  8   d  formed in the concave part  8   b  of the rear frame  8  is within the plate thickness of the front frame  9 , the bridge part  8   d  of the rear frame  8  is fitted into the hole  9   c  of the front frame  9 , without influence on the frame of the planer light source device. 
         [0045]    The other configurations are the same as in the embodiment 1. 
         [0046]    Though in the embodiments 1 and 2, the projection part  7   f  of the middle frame  7  and the lock part  8   c  of the rear frame  8  are engaged and fixed when the convex part  7   c  of the middle frame  7  and the concave part  8   b  of the rear frame  8  are fixed, as shown in  FIGS. 1 to 7 , the middle frame  7  and the rear frame  8  may be fixed via an adhesive resin such as a double-faced tape or adhesive without providing the projection part  7   f  or the lock part  8   c.    
         [0047]    Also, though in the embodiments 1 and 2, three convex parts  7   c  of the middle frame  7  are formed on one side face of the middle frame  7 , one convex part  7   c  may be provided on one side face of the middle frame  7  and fitted with the concave part  8   b  formed on the side face  8   a  of the rear frame  8 , whereby the area where the side face  8   a  of the rear frame  8  contacts the face  1   b  of the lamp reflector  1  is larger, and further the heat from the light source  2  can be diffused more efficiently. The position, number and shape of the convex part  7   c  can be arbitrarily determined in view of the overall structure of the planer light source device. 
         [0048]    Moreover, though in the embodiments 1 and 2, the convex part  7   c  of the middle frame  7  is provided on the side face at only one side, it may be provided on the side faces at opposed two sides or all the four sides, so that the middle frame  7  is connected with the rear frame  8  within the plate thickness of the rear frame  8 , allowing the side faces at all the four sides to be narrower frame. 
         [0049]    Also, in the embodiments, the convex part  7   c  of the middle frame  7  is formed in the direction (downward on the drawing) of the optical sheets  5  and fitted with the concave part  8   b  formed on the side face  8   a  of the rear frame  8 . However, as shown in  FIG. 8 , a convex part  8   e  may be formed on the side face  8   a  of the rear frame  8 , and a concave part  7   g  on the side face  7   b  of the middle frame  7  may be fitted with the convex part  8   e  on the side face  8   a  of the rear frame  8 . 
         [0050]    Though in the embodiments, the light guide plate  3  is like a board, the light guide plate is not limited to this form but may be like a wedge in which the thickness of the light guide plate  3  is smaller as the distance from the light source  2  is larger, whereby the incident light can be taken out efficiently and guided to the light emitting face  3   b  efficiently.