Abstract:
An apparatus for planar lighting configurable with light emitting devices is disclosed. The apparatus for planar lighting includes a plurality of light sources arranged on a circuit board; a reflective layer disposed on the circuit board; a transmission regulation layer disposed on the reflective layer and provided with a hole pattern allowing light to be transmitted therethrough, wherein a size of the hole disposed proximate to the light source is smaller than a size of the hole disposed between adjacent two light sources; a spacer disposed between the reflective layer and the transmission regulation layer such that the spacer maintains a distance between the reflective layer and the transmission regulation layer, wherein the spacer comprises at least one protrusion formed by bending a plate member; and an optical sheet disposed on the transmission regulation layer.

Description:
[0001]    This application claims the benefit of the Korean Patent Application No. 10-2013-0007295, filed on Jan. 23, 2013, which is hereby incorporated by reference as if fully set forth herein. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to an apparatus for planar lighting, and more particularly, to an apparatus for planar lighting that may be configured using light emitting devices. 
         [0004]    2. Discussion of the Related Art 
         [0005]    Among displays, a liquid crystal display (LCD) is used in a wide range of applications including televisions, laptop computers, desktop computer monitors, and mobile phones. 
         [0006]    Since LCDs are not self-emissive, a light emitting apparatus to illuminate the liquid crystal panel is needed to display image information. 
         [0007]    Since the light emitting apparatus of an LCD is coupled to the rear surface of the liquid crystal panel, it is often called a backlight unit. The backlight unit is an apparatus that forms a uniform surface light source and supplies the same to the backlight unit. 
         [0008]    A light emitting diode (LED) is structured by stacking an n-type semiconductor layer, a light emitting layer, and a p-type semiconductor layer on a substrate and forming electrodes on the p-type and n-type semiconductor layers. The LED emits light when recombination of electrons and holes supplied from semiconductor layers occurs in the light emitting layer and thereby light is produced and emitted outside. 
         [0009]    LEDs may be used as a light source of a backlight unit (BLU) by configuring an LED package. 
         [0010]    Since the backlight unit as described above provides a surface light source to the liquid crystal panel, it may be viewed as an example of an apparatus for planar lighting. Such a planar lighting apparatus, which is capable of uniformly emitting light through a flat surface, usually represent a relatively thin light source. 
         [0011]    Given the planar lighting apparatus as above, it may be possible to increase the lighting efficiency of a display and manufacture a slim display. 
       SUMMARY OF THE INVENTION 
       [0012]    Accordingly, the present invention is directed to an apparatus for planar lighting that substantially obviates one or more problems due to limitations and disadvantages of the related art. 
         [0013]    An object of the present invention is to provide an apparatus for planar lighting with a light guide layer which may provide a support structure to maintain a constant height of the light guide layer. 
         [0014]    Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
         [0015]    To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, an apparatus for planar lighting includes a plurality of light sources arranged on a circuit board; a reflective layer disposed on the circuit board; a transmission regulation layer disposed on the reflective layer and provided with a hole pattern allowing light to be transmitted therethrough, wherein a size of the hole disposed proximate to the light source is smaller than a size of the hole disposed between adjacent two light sources; a spacer disposed between the reflective layer and the transmission regulation layer such that the spacer maintains a distance between the reflective layer and the transmission regulation layer, wherein the spacer comprises at least one protrusion formed by bending a plate member; and an optical sheet disposed on the transmission regulation layer. 
         [0016]    In another aspect of the present invention, there is provided an apparatus for planar lighting including a plurality of light sources arranged on a circuit board; a reflective layer disposed on the circuit board; a transmission regulation layer disposed on the reflective layer and provided with a hole pattern allowing light to be transmitted therethrough, wherein a size of the hole disposed proximate to the light source is smaller than a size of the hole disposed between adjacent two light sources; a spacer disposed between the reflective layer and the transmission regulation layer to form a light guide layer, wherein the spacer maintains a distance between the reflective layer and the transmission regulation layer, and wherein the spacer is provided with at least one protrusion connected through an extension portion; and an optical sheet disposed on the transmission regulation layer. 
         [0017]    It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings: 
           [0019]      FIG. 1  is a cross-sectional view illustrating an apparatus for planar lighting according to an embodiment; 
           [0020]      FIG. 2  is a perspective view illustrating an example of a spacer; 
           [0021]      FIGS. 3 to 5  are cross-sectional views schematically illustrating various examples of the spacer; 
           [0022]      FIGS. 6 to 10  are plan views schematically illustrating various examples of an arrangement of light sources and a spacer; 
           [0023]      FIGS. 11 to 14  are cross-sectional views schematically illustrating various examples of a spacer including a protrusion to cover the light source; and 
           [0024]      FIG. 15  is a cross-sectional view illustrating another example of a spacer. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    Reference will now be made in detail to the preferred embodiments of the present invention. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
         [0026]    Various modifications and variations are possible in the present invention, and a few specific embodiments are exemplarily shown in the accompanying drawings and described in detail below. However, these are not intended to limit the scope of the present invention. Various equivalents and modifications may be made without departing from the spirit of the invention, which is defined in the claims. 
         [0027]    As used herein, the term “on” in the context of a layer, region, or substrate disposed on another constituent means that the layer, region, or substrate is disposed directly on another constituent or indirectly on another constituent with an element interposed. 
         [0028]    In the disclosure below, the terms “first” and “second” may be used to describe various elements, components, regions, layers, and/or areas. It should be understood that the elements, components, regions, layers, and/or areas are not limited by these terms. 
         [0029]      FIG. 1  is a cross-sectional view illustrating an apparatus for planar lighting according to an embodiment. 
         [0030]    A planar lighting apparatus  20  may be disposed on a lower cover  16 , and a liquid crystal panel (not shown) may be disposed on the planar lighting apparatus  20 . 
         [0031]    The planar lighting apparatus  20  includes a plurality of light sources  22  mounted on a circuit board  21  disposed at the upper side of the lower cover  16 . The light sources  22  may be mounted on the circuit board  21  in a manner that a light emitting diode (LED) package is surface-mounted on the circuit board  21 . 
         [0032]    In such a light source  22  including the LED package, a pair of electrodes  222  may be arranged through a sub-mount substrate  221 , an LED  223  is connected and mounted to the electrodes  222 , and a fluorescent layer  224  having a mixed silicone resin may be disposed at the outer side of the LED  223 . 
         [0033]    In addition, the upper surface of the fluorescent layer  224  may be flat, and an optical layer  225  having an optical property of reflection or transmission may be disposed on the upper surface of the fluorescent layer  224 . 
         [0034]    The optical layer  225  may be formed of a material manufactured by mixing phenylpropanolamine (PPA), epoxy molding compound (EMC), micro cell polyethylene terephthalate (MCPET), silver (Ag), and aluminum (Al) having a high reflectivity with a bead having physical properties of reflection, transmission or refraction such as titanium (Ti), aluminum (Al), silver (Ag) and silicon dioxide (SiO 2 ) and a resin. 
         [0035]    The light emitted upward from the LED  223  by the optical layer  225  may be reflected toward the side of the fluorescent layer  234 . Herein, the LED  223  may be a blue LED, and the fluorescent substance constituting the fluorescent layer  234  may be a yellow phosphor. Thereby, white light may be emitted from the light source  22 . 
         [0036]    The light source  22  installed on the circuit board  21  may be disposed in a seating groove  161  provided on the upper surface of the lower cover  16 . In addition, the seating grooves  161  may be arranged spaced a certain distance from each other, and thereby the circuit boards  21  disposed on the seating grooves  161  may also be arranged spaced a certain distance from each other. Accordingly, the light sources  22  may be arranged spaced a certain distance from each other on the lower cover  16 . 
         [0037]    Such light sources  22  may be arranged in a line, or in a zigzag pattern. 
         [0038]    At this time, a reflective layer  23  may be disposed in the space between the light sources  22  on the circuit board. Thereby, the light sources  22  may protrude above the reflective layer  23 . 
         [0039]    In addition, a transmission regulation layer  15  provided with a pattern of holes  151  arranged a certain distance from the reflective layer  23  and allowing light to be transmitted therethrough may be disposed on the reflective layer  23 . 
         [0040]    The transmission regulation layer  15  may be a reflective sheet which causes a part of light emitted by the light sources  22  to be transmitted therethrough and reflects the remainder thereof. 
         [0041]    The transmission regulation layer  15  may be implemented by a hole patterned reflective sheet having a plurality of holes  151 . That is, light emitted from the light sources  22  or reflected from the reflective layer  23  may be transmitted through the holes  151 , and the light incident on the other regions may be reflected back to the reflective layer  23  or refracted or reflected by a spacer  30 . 
         [0042]    The radius of the holes  151  may increase as the distance from the center of the light source  22  increases such that transmissivity of light becomes greater than the reflectivity of light as the distance from the light source  22  increases. 
         [0043]    That is, the size of the hole  151  disposed between adjacent two light sources  22  is greater than the other holes  151 . 
         [0044]    In addition, the size of the holes  151  increases with a distance from a position on a light source toward a position between adjacent two light sources. And then, the size of the holes  151  decreases as a distance from the position between adjacent two light sources increases. 
         [0045]    The light intensity increases when the distance from the light source  22  decreases, while the light intensity decreases when the distance increases. Accordingly, to maintain uniform luminance throughout the entire display panel employing the planar lighting apparatus, the amount of transmitted light may need to be increased as the distance from the light source  22  increases. 
         [0046]    In this way, the light emitted from the light source through the space between the reflective layer  23  and the transmission regulation layer  15  diffuses in a lateral direction. The light diffusing in this manner is emitted upward through the pattern of holes  151 . The space arranged between the reflective layer  23  and the transmission regulation layer  15  to allow light to diffuse therethrough may be defined as a light guide layer  24 . 
         [0047]    The light guide layer  24  may be formed by a spacer  30  disposed between the reflective layer  23  and the transmission regulation layer  15  to maintain a certain distance between the reflective layer  23  and the transmission regulation layer  15 . 
         [0048]    That is, the spacer  30  may function to maintain a constant distance between the transmission regulation layer  15  and the light source  22 , and may extend to a height corresponding to the height as designed and a length corresponding to the length of the reflective layer  23 . 
         [0049]    The spacer  30  may be formed of polycarbonate (PC), polymethyl methacrylate (PMMA), glass, resin, phenylpropanolamine (PPA), or aluminum (Al) so as to transmit, refract, or reflect light. 
         [0050]    Accordingly, in addition to the mechanical property of maintaining the distance between the reflective layer  23  and the transmission regulation layer  15 , the spacer  30  may cause interfacial reflection of the light emitted from the light source  22 . About 20% to 50% of the emitted light may diffuse through interfacial reflection. 
         [0051]    The spacer  30  includes a protrusion  34  protruding from the reflective layer  23  by being bent toward the transmission regulation layer  15 . The spacer  30  including the protrusion  34  formed in a bent fashion may minimize the deviation of heights of the protrusions  34  and secure a certain size of the light guide layer  24 . 
         [0052]    In addition, optical sheets such as a diffusion layer  11 , a lower polarizing plate  12 , a color filter board, and an upper polarizing plate may be disposed on the transmission regulation layer  15 . 
         [0053]    Meanwhile, an adhesive  17  may be applied to the bottom surfaces of the circuit board  21  and the reflective layer  23 . Thereby, the circuit board  21  may be fixed to the seating groove  161  of the lower cover  16 , and the reflective layer  23  may be fixed to the circuit board  21 . 
         [0054]    As shown in  FIG. 2 , the spacer  30  may be provided with the protrusion  34  by bending a film having a relatively constant thickness. A plurality of such protrusions  34  may be arranged along the periphery of the light source  22 . In this case, the thickness of the film constituting the spacer  30  may vary depending upon position. 
         [0055]    The thickness of the film constituting the spacer  30  may be between 50 μm and 500 μm. 
         [0056]    As shown in  FIGS. 2 and 3 , the protrusion  34  of the spacer  30  is formed by being bent from an extension portion  35  close to the reflective layer  23  toward the transmission regulation layer  15 . 
         [0057]    Accordingly, the protrusion  34  is provided with a first wall  31  and a second wall  32  substantially perpendicularly disposed between the reflective layer  23  and the transmission regulation layer  15 , and a third wall  33  arranged between the first and second walls to be close to the transmission regulation layer  15 . That is, the third wall  33  forms the top of the protrusion  34 . 
         [0058]    By such bent walls  31 ,  32  and  33 , a space  36  is defined therein. The height of the space  36  approximates to the height of the spacer  30  forming the light guide layer  24 . 
         [0059]    The spacer  30  may be attached to the transmission regulation layer  15  by applying an adhesive  40  to the space between the third wall  33  forming the upper surface of the spacer  30  and the transmission regulation layer  15 . At this time, an ultraviolet curing process or a thermal curing process may be used 
         [0060]    In addition, the extension portion  35  forming the lower surface of the spacer  30  and the reflective layer  23  may also be attached to each other by applying the adhesive  40  therebetween. 
         [0061]    As the protrusion  34  is bent to form a concave-convex structure, a three-dimensional structure may be formed. 
         [0062]    As shown in  FIG. 2 , the protrusion  34  may be formed in a ring shape along the periphery of the light source  22 . Accordingly, the number of the protrusions  34  may be equal to or greater than the number of the light source  22 . That is, a plurality of ring-shaped protrusions  34  may be regularly arranged. Alternatively, the protrusions  34  may be formed in various shapes such as a straight bar, a bent bar, a circular column, and a cone. 
         [0063]    As shown in  FIG. 2 , when the protrusions  34  are disposed along the periphery of each light source  22 , the protrusions  34  may be connected to each other by the extension portion  35 . 
         [0064]    In  FIG. 3 , the extension portion  35  covers a mount hole  26  in which the light source  22  is installed. Alternatively, an open hole  37  may be provided to the extension portion  35  such that the light source  22  is disposed through the open hole  37 , as shown in  FIG. 2 . 
         [0065]    Referring to  FIG. 4 , the light source  22  is arranged to protrude from the mount hole  26  (see  FIG. 3 ) formed in the reflective layer  23 . Herein, the light source  22  may be arranged at a position corresponding to the position of the open hole  37  of the spacer  30 . Other details are the same as those described above with reference to  FIGS. 2 and 3 . 
         [0066]    Meanwhile, the sidewall of the protrusion  34  may be inclined as shown in  FIG. 5 . That is, the cross section of the protrusion  34  may be provided with a first wall  31   a  and a second wall  32   a  which are inclined in the opposite directions. 
         [0067]    In some cases, the sidewalls  31   a  and  32   a  of the protrusion  34  may increase the efficiency of diffusion of light from the light source  22  in the lateral direction. 
         [0068]    Other details are the same as those described above with reference to  FIGS. 2 and 3 . 
         [0069]      FIG. 6  is a plan view illustrating an example of an embodiment exemplarily shown in  FIGS. 2 and 3 . 
         [0070]    As shown in  FIG. 6 , the spacer  30  is provided with a plurality of protrusions  34  arranged at positions corresponding to the positions of the light sources  22 . 
         [0071]    That is,  FIG. 6  shows the light sources  22  arranged in a square fashion, and the protrusions  34  arranged at positions corresponding to the positions of the light sources  22 . The third wall  33  forming the top surface of the protrusion  34  may substantially support the upper structure (for example, the transmission regulation layer  15 ). 
         [0072]    The open hole  37  may be disposed between each of the protrusions  34  and the corresponding light source  22 , and the protrusions  34  may be connected to each other by the extension portion  35 . 
         [0073]    Referring to  FIG. 7 , the light sources  22  are arranged in a zigzag pattern, i.e., in a triangular shape, the protrusions  34  of the spacer  30  are arranged at positions corresponding to the light sources  22 . 
         [0074]    Meanwhile, as shown in  FIG. 8 , auxiliary protrusions  38  may be further provided between the protrusions in addition to the configuration shown in  FIG. 6 . 
         [0075]    As shown in  FIG. 8 , the auxiliary protrusions  38  may be arranged in a mesh structure or a checkerboard pattern, or various other patterns. 
         [0076]    In addition, as shown in  FIG. 9 , protrusions  39  radially disposed with respect to each light source  22  may be provided. That is, a plurality of protrusions  39  arranged about the light source  22 , spaced a certain distance (or a certain angle) from each other, and extending in a radial direction may be provided. The protrusions  39  may be connected to each other by the extension portion  35 . 
         [0077]    As the spacer  30  includes the protrusions  39  radially disposed with respect to the light source  22 , interference between the light emitted from the light source  22  and the spacer  30  may be minimized. 
         [0078]      FIGS. 10 to 12  show a configuration having protrusion  34  covering the light source  22 . Each of the protrusions  34  includes a third wall  33   a  disposed on the corresponding light source  22 . The third walls  33   a  may support the transmission regulation layer  15 . 
         [0079]    As the spacer  30  is provided with such protrusions  34 , reflection of the light emitted from the light source  22  may be improved through specular reflection from the spacer  30 , leading to increase of the overall efficiency of the planar lighting apparatus. 
         [0080]    That is, the spacer  30  configured as above may improve not only mechanical stability in supporting the transmission regulation layer  15  but also optical properties. 
         [0081]    In addition, a second protrusion  34   a  may be disposed around the protrusion  34  (hereinafter, a first protrusion) covering the light source  22 . The description given above with reference to  FIGS. 2 and 3  is directly applicable to the second protrusion  34   a . That is, the second protrusion  34   a  may be disposed around the light source  22  in a ring shape. 
         [0082]    As shown in  FIG. 13 , the third wall  33  of the first protrusion  34  covering the light source  22  may include curved portions  33   b  and  33   c  formed in a lens shape. 
         [0083]    That is, the third wall  33  extending from the first wall  31  and the second wall  32  may be provided with curved portions  33   b  and  33   c  extending toward the light source  22 . 
         [0084]    The curved portions  33   b  and  33   c  may allow the light emitted upward from the light source  22  to be more efficiently diffused. 
         [0085]    Accordingly, the first protrusion  34  may support the transmission regulation layer  15  and maximize the optical property of diffusion. 
         [0086]    Meanwhile, as shown in  FIG. 14 , the second protrusion  34   b  disposed at the periphery of the light source  22  may be arranged to penetrate the transmission regulation layer  15  and support the optical sheets  11 ,  12 ,  13  and  14 . 
         [0087]    That is, the first protrusion  34  covering the light source  22  supports the transmission regulation layer  15 , and the second protrusion  34   b  supports the optical sheets  11 ,  12 ,  13  and  14  by penetrating the transmission regulation layer  15 . 
         [0088]    By the second protrusion  34   b , an air gap may be formed between the transmission regulation layer  15  and the optical sheets  11 ,  12 ,  13  and  14 . A light diffusion gap  40  allowing light to diffuse therethrough may be defined by the air gap. 
         [0089]      FIG. 15  shows an example of the spacer  30  configured by combining protrusions  34  and  341  forming two layers. 
         [0090]    That is, the film including the lower side of the protrusion  34  may allow the extension portion  35  to support the reflective layer  23 , and the film including the upper side of the protrusion  341  may allow the upper surface of the protrusion  341  to support the transmission regulation layer  15 . The two protrusions  34  and  341  may be combined with each other. 
         [0091]    For example, the two protrusions  34  and  341  may be combined with each other by a projection and a groove  301 . For example, a groove may be provided to the lower side of the protrusion  34 , and the upper side of the protrusion  341  may be provided with a projection to be coupled to the groove such that the two protrusions  34  and  341  are combined with each other. 
         [0092]    For other details, the description given above is applicable. That is, various embodiments have been described above and a description of one embodiment may be applied to another embodiment. 
         [0093]    It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.