Abstract:
A light guide plate having a top surface through which light is emitted, a bottom surface opposite to the top surface and a side surface between the top and bottom surfaces, a bottom reflector on the bottom surface for reflecting light at the bottom surface back into the light guide plate, light emitting diodes at the side surface and a side reflector on the side surface for reflecting light at the side surface back into the light guide plate, wherein the side reflector on the side surface has an opening corresponding to at least one of the light emitting diodes

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The embodiments of the invention relate to Light Emitting Diode (LED) lighting, and more particularly, to a LED lighting with a light guide plate having a side reflector. Although embodiments of the invention are suitable for a wide scope of applications, it is particularly suitable for increasing the light redirection efficiency of a light guide plate receiving light from a light emitting diode. 
         [0003]    2. Discussion of the Related Art 
         [0004]    In general, LED lighting is either a direct type or a dispersion type. The direct type of LED lighting has light emitting diodes that emit light directly through a lens or directly through a diffuser. The dispersion type of LED lighting has light emitting diodes that emit light into a waveguide, which redirects and disperses the light. Although a diffuser can minimize the harshness of the light from a direct type of LED lighting, the dispersed light from a dispersion type of LED lighting is easier on the eyes. 
         [0005]      FIG. 1   a  is an exploded perspective of dispersion type LED lighting according to the prior art. As shown in  FIG. 1 , the LED lighting  100  according to the prior art includes a light guide plate  101 , LEDs  110  on first and second light strips  121  and  122 , a bottom reflector  130  and side reflectors  131 - 134  that surround the light guide plate  101 . The light guide plate  101  has a top surface  101   a  through which light is emitted, side surfaces  101   b - 101   e  through which light can be emitted or received, and bottom surface  101   f  at which light is reflected by the bottom reflector  130 . The LEDs  110  on first and second light strips  121  and  122  emit light into two opposing side surfaces  101   b  and  101   d  of the light guide plate  101 . The side reflectors  131 - 134  surrounding the light guide plate  101  reflect light from the side surfaces  101   b - 101   e  back into the side surfaces  101   b - 101   e , respectively. The first and second light strips  121  and  122  have a reflective capability to also reflect light from the side surfaces  101   b - 101   e  back into the side surfaces  101   b - 101   e , respectively. 
         [0006]      FIG. 1   b  is an assembled perspective view of the prior art.  FIG. 1   c  is a cross-sectional view along the line I-I′ of the assembled perspective view shown in  FIG. 1   b . As shown in  FIGS. 1   b  and  1   c , the side reflectors  131 - 134  cover a peripheral portion of the top surface  101   a  when the LED lighting  100  is assembled. Such a covering of the top surface  101   a  reduces the light output from the LED lighting  100 . 
         [0007]    As also shown in  FIG. 1   c , the reflected light L 1  is light from a side surface  101   b  that is reflected by the side reflector  131  back into the side surface  101   b  of the light guide plate  101 . However, light from the side surface that is reflected many times by the side-reflector, such as reflected light L 2 , is not as bright as the reflected light L 1 . Light reflected off of the light strip, such as reflected light L 3 , or reflected off both of the light strip and the side reflector, such as reflected light L 4 , has even further reduced brightness than the reflected light L 1 , which is light reflected directly back into a side surface by a side reflector. Such reductions in the brightness of reflected light decreases the light redirection efficiency because light, which initially came from the LEDs  110 , is lost and can not be redirected through the top surface  101   a  of the light guide plate  101 . 
       SUMMARY OF THE INVENTION 
       [0008]    Accordingly, embodiments of the invention are directed to a LED lighting with a light guide plate having a side reflector that substantially obviates one or more of the problems due to limitations and disadvantages of the related art. 
         [0009]    An object of embodiments of the invention is to provide a side reflector for light guide plate of LED lighting that prevents light loss. 
         [0010]    Another object of embodiments of the invention is to provide a side reflector for light guide plate of LED that increases the light redirection efficiency. 
         [0011]    Additional features and advantages of embodiments of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of embodiments of the invention. The objectives and other advantages of the embodiments of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
         [0012]    To achieve these and other advantages and in accordance with the purpose of embodiments of the invention, as embodied and broadly described, the LED lighting includes a light guide plate having a top surface through which light is emitted, a bottom surface opposite to the top surface and a side surface between the top and bottom surfaces, a bottom reflector on the bottom surface for reflecting light at the bottom surface back into the light guide plate, light emitting diodes at the side surface and a side reflector on the side surface for reflecting light at the side surface back into the light guide plate, wherein the side reflector on the side surface has an opening corresponding to at least one of the light emitting diodes. 
         [0013]    In another aspect, the LED lighting includes a light guide plate having a top surface through which light is emitted, a bottom surface opposite to the top surface and side surfaces between the top and bottom surfaces, a bottom reflector on the bottom surface for reflecting light at the bottom surface back into the light guide plate, a light strip having a plurality of light emitting diodes at least at one of the side surfaces, side reflectors on each of the side surfaces for reflecting light at the side surfaces back into the light guide plate, wherein a side reflector on the at least one of the side surfaces is positioned between the light guide plate and the light strip, and has an opening corresponding to at least one of the plurality of light emitting diodes. 
         [0014]    In yet another aspect, the LED lighting includes a light guide plate having a top surface through which light is emitted, a bottom surface opposite to the top surface and side surfaces between the top and bottom surfaces, a bottom reflector on the bottom surface for reflecting light at the bottom surface back into the light guide plate, first and second pluralities of light emitting diodes respectively at opposing side surfaces, and side reflectors on each of the side surfaces for reflecting light at the side surfaces back into the light guide plate, wherein side reflectors at the opposing side surfaces each have at least an opening corresponding to at least one of the first and second pluralities of light emitting diodes. 
         [0015]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of embodiments of the invention as claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of embodiments of the invention. 
           [0017]      FIG. 1   a  is an exploded perspective of dispersion type LED lighting according to the prior art. 
           [0018]      FIG. 1   b  is an assembled perspective view of the prior art. 
           [0019]      FIG. 1   c  is a cross-sectional view along the line I-I′ of the assembled perspective view shown in  FIG. 1   b.    
           [0020]      FIG. 2   a  is an exploded perspective view of a first exemplary embodiment of the invention. 
           [0021]      FIG. 2   b  is an assembled perspective view of the first exemplary embodiment of the invention. 
           [0022]      FIG. 3   a  is an exploded perspective view of a second exemplary embodiment of the invention. 
           [0023]      FIG. 3   b  is an assembled perspective view of the second exemplary embodiment of the invention. 
           [0024]      FIG. 4   a  is an exploded perspective view of a third exemplary embodiment of the invention. 
           [0025]      FIG. 4   b  is an assembled perspective view of the third exemplary embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]    Reference will now be made in detail to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. In the drawings, the thicknesses of layers and regions are exaggerated for clarity. Like reference numerals in the drawings denote like elements. 
         [0027]      FIG. 2   a  is an exploded perspective view of a first exemplary embodiment of the invention. As shown in  FIG. 2   a , the LED lighting  200  according to the first exemplary embodiment includes a light guide plate  101 , LEDs  210   a  and  210   b  on first and second light strips  221  and  222 , a bottom reflector  230  and side reflectors  231 - 234  on the sides of the light guide plate  101 . The light guide plate  101  has a top surface  101   a  through which light is emitted, side surfaces  101   b - 101   e  at which light is reflected by the side reflectors  231 - 234 , and bottom surface  101   f  at which light is reflected by the bottom reflector  230 . The top surface  101   a  opposes the bottom surface  101   f  and the side surfaces  101   b - 101   e  are located between the top surface  101   a  and the bottom surface  101   f . The LEDs  210   a  and  210   b  on first and second light strips  221  and  222  emit light into two opposing side surfaces  101   b  and  101   d  of the light guide plate  101 . The side reflectors  231 - 234  are positioned on each of the side surfaces  101   b - 101   e  so as to reflect light at the side surfaces back into the light guide plate  101 . 
         [0028]    The side reflectors  232  and  234  on side surfaces  101   b  and  101   d  cover all of side surfaces  101   b  and  101   d . The side reflectors  231  and  233  on side surfaces  101   b  and  101   d  have slit openings  241  and  242 , respectively. The slit opening  241  corresponds to LEDs  210   a  on the first light strip  221 . The slit opening  242  corresponds to LEDs  210   b  on the second light strip  222 . The side reflector  231  is positioned between side surfaces  101   b  and the first light strip  221 . The side reflector  233  is positioned between side surfaces  101   d  and the second light strip  222 . 
         [0029]    The side reflector  231  on side surface  101   b  reflects light, which travels directly across the light guide plate  101  from the LEDs  210   b  on the second light strip  222 , back into the light guide plate  101 . The side reflector  233  on side surface  101   d  reflects light, which travels directly across the light guide plate  101  from the LEDs  210   a  on the first light strip  221 , back into the light guide plate  101 . By reflecting light that travels directly across the light guide plate  101  from the LEDs  210   a  and  210   b  at the side surfaces  101   b  and  101   d  through which light is received from the LEDs  210   a  and  210   b , the light redirection efficiency is improved. 
         [0030]    The side reflectors  231 - 234  in the first exemplary embodiment shown in  FIG. 2   a  are coated onto the light guide plate  101 . For example, the side reflectors  231 - 234  can be a painted layer applied using a paint sprayer. In another example, the side reflectors  231 - 234  can be a deposited layer applied using chemical vapor deposition, plasma deposition or some other type of deposition process that can deposit a metallic layer. 
         [0031]    A mask can be used for the slit openings  241 , and the top and bottom surfaces  101   a  and  101   f  of the light guide plate  101  during the coating process for the side reflectors  231 - 234 . In that alternative, the bottom surface  101   f  can also be coated so as to alleviate the need for a separate bottom reflector  130 . The masking defines the slit openings and prevents any coating of side reflector material onto the top surface  101   a  of the light guide plate  101 . By providing the side reflectors on the side surfaces  101   b - 101   d  such that side reflectors do not overlap onto the top surface  101   a  of the light guide plate  101 , light loss is prevented in the LED lighting  200 . 
         [0032]      FIG. 2   b  is an assembled perspective view of the first exemplary embodiment of the invention. As shown in  FIG. 2   b , LEDs  210   a  on the first light strip  221  can be positioned within the slit opening  241  of the side reflector  231 . Further, the LEDs  210   a  on the first light strip  221  can be adhesively attached to side surface  101   b  of the light guide plate  101 . The LEDs  210   b  on the second light strip  222  can be positioned within the slit opening  242  of the side reflector  233 . Further, the LEDs  210  on the second light strip  222  can be adhesively attached to side surface  101   d  of the light guide plate  101 . 
         [0033]      FIG. 3   a  is an exploded perspective view of a second exemplary embodiment of the invention. As shown in  FIG. 3   a , the LED lighting  300  according to the second exemplary embodiment includes a light guide plate  101 , LEDs  310   a  and  310   b  on first and second light strips  321  and  322 , a bottom reflector  330  and side reflectors  331 - 334  that are adhesively bonded to the sides of the light guide plate  101 . The light guide plate  101  has a top surface  101   a  through which light is emitted, side surfaces  101   b - 101   e  at which is reflected by the side reflectors  331 - 334 , and bottom surface  101   f  at which light is reflected by the bottom reflector  330 . The top surface  101   a  opposes the bottom surface  101   f  and the side surfaces  101   b - 101   e  are located between the top surface  101   a  and the bottom surface  101   f . The LEDs  310   a  and  310   b  on first and second light strips  321  and  322  emit light into two opposing side surfaces  101   b  and  101   d  of the light guide plate  101 . The side reflectors  331 - 334  are adhered onto each of the side surfaces  101   b - 101   e  so as to reflect light at the side surfaces back into the light guide plate  101 . 
         [0034]    The side reflectors  332  and  334  on side surfaces  101   b  and  101   d  cover all of side surfaces  101   b  and  101   d . The side reflectors  331  and  333  on side surfaces  101   b  and  101   d  each have single aperture openings  341  and  342 , respectively. The single aperture opening  341  corresponds to LEDs  310   a  on the first light strip  321 . The single aperture opening  342  corresponds to LEDs  310   b  on the second light strip  322 . The side reflector  331  is positioned between side surfaces  101   b  and the first light strip  321 . The side reflector  333  is positioned between side surfaces  110   d  and the second light strip  322 . 
         [0035]    The side reflector  331  on side surface  101   b  reflects light, which travels directly across the light guide plate  101  from the LEDs  310   b  on the second light strip  322 , back into the light guide plate  101 . The side reflector  333  on side surface  110   d  reflects light, which travels directly across the light guide plate  101  from the LEDs  310   a  on the first light strip  321 , back into the light guide plate  101 . A side reflector having a single aperture opening reflects more light directly into the light guide plate  101  at the side surface than a side reflector having a slit opening, as described in the first embodiment, because of the increased surface area of such a side reflector at ends of the side reflector. By reflecting light that travels directly across the light guide plate  101  from the LEDs  310   a  and  310   b  at the side surfaces  101   d  and  101   b  through which light is received from the LEDs  310   b  and  310   a , the light redirection efficiency is improved. 
         [0036]    The side reflectors  331 - 334  in the second exemplary embodiment shown in  FIG. 3   a  are adhesively applied onto the light guide plate  101 . For example, the side reflectors without openings can be stickers while the side reflectors with openings can be backed stickers such that a sticker with an opening can be applied correctly to a side surface and then the backing is removed. The edges of such stickers can be trimmed so that the stickers are only on the side surfaces of the light guide plate. In another example, the side reflectors  331 - 334  can be a tape applied to the side surfaces with the edges of the tape being trimmed so that the tape is only on the side surfaces and the openings are then cut out from the tape. By providing the side reflectors on the side surfaces  101   b - 101   d  such that side reflectors do not overlap onto the top surface  101   a  of the light guide plate  101 , light loss is prevented in the LED lighting  300 . 
         [0037]      FIG. 3   b  is an assembled perspective view of the second exemplary embodiment of the invention. As shown in  FIG. 3   b , LEDs  310   a  on the first light strip  321  can be positioned within the single aperture opening  341  of the side reflector  331 . Further, the LEDs  310   a  on the first light strip  321  can be adhesively attached to side surface  101   b  of the light guide plate  101 . The LEDs  310   b  on the second light strip  322  can be positioned within the single aperture opening  342  of the side reflector  333 . Further, the LEDs  310   b  on the second light strip  322  can be adhesively attached to side surface  101   d  of the light guide plate  101 . In the alternative, the openings in the side reflectors  331  and  333  can be strip openings, such as described in the first embodiment, to simplify alignment of the LEDs to the openings in the side reflectors but the light redirection efficiency of the lighting device will be slightly decreased. 
         [0038]      FIG. 4   a  is an exploded perspective view of a third exemplary embodiment of the invention. As shown in  FIG. 4   a , the LED lighting  400  according to the third exemplary embodiment includes a light guide plate  101 , LEDs  410   a - 410   d  on first, second, third and fourth light strips  421 - 424 , a bottom reflector  430  and side reflectors  431 - 434  that are adhesively bonded to the sides of the light guide plate  101 . The light guide plate  101  has a top surface  101   a  through which light is emitted, side surfaces  101   b - 101   e  at which is reflected by the side reflectors  431 - 434 , and bottom surface  101   f  at which light is reflected by the bottom reflector  430 . The top surface  101   a  opposes the bottom surface  101   f  and the side surfaces  101   b - 101   e  are located between the top surface  101   a  and the bottom surface  101   f . The LEDs  410   a  and  410   b  on first and second light strips  421  and  422  emit light into two opposing side surfaces  101   b  and  101   d  of the light guide plate  101 . The LEDs  410   c  and  410   d  on third and fourth light strips  423  and  424  emit light into two other opposing side surfaces  101   c  and  101   e  of the light guide plate  101 . The side reflectors  431 - 434  are adhered onto each of the side surfaces  101   b - 101   e  so as to reflect light at the side surfaces back into the light guide plate  101 . 
         [0039]    The side reflectors  431 - 434  on side surfaces  101   b - 101   e  have aperture openings  441 - 444 , respectively. The aperture openings  441  respectively correspond to LEDs  410   a  on the first light strip  421 . The aperture openings  442  respectively correspond to LEDs  410   b  on the second light strip  422 . The aperture openings  443  respectively correspond to LEDs  410   c  on the third light strip  423 . The aperture openings  444  respectively correspond to LEDs  410   d  on the fourth light strip  424 . The side reflector  431  is positioned between side surfaces  101   b  and the first light strip  421 . The side reflector  432  is positioned between side surfaces  101   c  and the third light strip  423 . The side reflector  433  is positioned between side surfaces  101   d  and the second light strip  422 . The side reflector  434  is positioned between side surfaces  101   e  and the fourth light strip  424 . 
         [0040]    The first side reflector  431  on side surface  101   b  reflects light, which travels directly across the light guide plate  101  from the LEDs  410   b  on the second light strip  422 , back into the light guide plate  101 . The second side reflector  433  on side surface  101   d  reflects light, which travels directly across the light guide plate  101  from the LEDs  410   a  on the first light strip  421 , back into the light guide plate  101 . The third side reflector  432  on side surface  101   c  reflects light, which travels directly across the light guide plate  101  from the LEDs  410   d  on the fourth light strip  424 , back into the light guide plate  101 . The fourth side reflector  434  on side surface  101   e  reflects light, which travels directly across the light guide plate  101  from the LEDs  410   c  on the third light strip  423 , back into the light guide plate  101 . A side reflector having respective aperture openings for each of the LEDs reflects more light directly into the light guide plate at the side surfaces than a side reflector having a slit opening, as described in the first embodiment, or a side reflector having a single aperture, as described in the second embodiment, because of the increased surface area of such a side reflector at ends of the side reflector and in between the LEDs. By reflecting light that travels directly across the light guide plate  101  from the LEDs  410   a ,  410   b ,  410   c  and  410  at the side surfaces  101   d ,  101   b ,  101   e  and  101  through which light is received from the LEDs  410   b ,  410   a ,  410   d  and  410   c , the light redirection efficiency is improved. 
         [0041]    The side reflectors  431 - 434  in the third exemplary embodiment shown in  FIG. 4   a  are adhesively applied onto the light guide plate  101 . For example, the side reflectors can be painted, metalized or metallic templates that each have a plurality of apertures. The base material of the template can be a fibrous material, an elastomer, a plastic or a metal. An example of a fibrous material is cardboard or cardstock. An example of an elastomer is silicone, rubber or foam. The size of such templates matches or is slightly less than the side surfaces of the light guide plate while the thickness of such templates is larger or the same as the distance at which the LEDs protrude from the light strips. By providing the side reflectors only on the side surfaces  101   b - 101   d  of the light guide plate  101  such that side reflectors do not overlap onto the top surface  101   a  of the light guide plate  101 , light loss is prevented in the LED lighting  400 . 
         [0042]      FIG. 4   b  is an assembled perspective view of the third exemplary embodiment of the invention. As shown in  FIG. 4   b , LEDs  410   a  on the first light strip  421  are respectively positioned within the aperture openings  441  of the first side reflector  431 . LEDs on the third light strip  423  can be respectively positioned within the aperture openings  443  of the second side reflector  432 . Further, LEDs on the second light strip  422  can be respectively positioned within the aperture openings of a third side reflector  433  and LEDs on the fourth light strip  424  can be respectively positioned within the aperture openings of the fourth side reflector  434 . 
         [0043]    The LEDs can be adhesively attached to the side reflectors. In the alternative, the light strips can be adhesively attached to the side reflectors. In yet another alternative, both the LEDs and the light strips are adhesively attached to the side reflectors. 
         [0044]    The openings in the side reflectors can be strip openings, such as described in the first embodiment, or a single aperture opening, such as described in the second embodiment, to simplify alignment of the LEDs to the openings in the side reflectors but the light redirection efficiency of the light device will be decreased. Although rectangular lighting devices are shown in the first, second and third embodiments, the lighting devices according to embodiments of the invention can have any polygonal shape, curves or any combination of curved sides and straight sides. For example, the lighting devices according to embodiments of the invention can have a circular shape, elliptical shape or a trapezoidal shape. 
         [0045]    It will be apparent to those skilled in the art that various modifications and variations can be made in the embodiments of the invention without departing from the spirit or scope of the invention. Thus, it is intended that embodiments of the invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.