Patent Publication Number: US-2016245491-A1

Title: Transparent light emitting apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 2015-0026675, filed on Feb. 25, 2015, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to a transparent light emitting apparatus using light emitting diodes (LED). 
     2. Discussion of Related Art 
     Recently, transparent light emitting apparatuses have been generally used in lightings, indoor and outdoor advertising boards, billboards, and signs. In a transparent light emitting apparatuses, transparent wiring is formed on a glass substrate and a light emitting diode (LED) is connected to the transparent wiring. 
     Light emitting apparatuses using LEDs are driven using low power and have a long life, and thus used in various fields such as large outdoor electronic boards and indoor small electronic displays. 
     However, in the case of indium tin oxide (ITO) used as transparent wiring, since an LED cannot be directly soldered thereto, a manufacturing process becomes complicated and thermal resistance is high. 
     Also, ITO is expensive and easily damaged by flexure or other physical stresses. Also, to obtain high conductivity, high deposition temperature and/or high annealing temperature are necessary. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a transparent light emitting apparatus which is manufactured through a simple process and is able to reduce manufacturing costs. 
     The present invention is also directed to a flexible transparent light emitting apparatus. 
     According to an aspect of the present invention, there is provided a transparent light emitting apparatus including a first transparent substrate, a wiring sheet including a base layer disposed on the first transparent substrate and a plurality of wiring electrodes formed on the base layer, and a plurality of light emitting diode (LED) packages electrically connected to the wiring electrodes. 
     Each of the wiring electrodes may be made of a conducting wire having a width of from about 2 μm to about 20 μm. 
     Each of the wiring electrodes may include metal mesh. 
     The base layer may have a thickness of from about 50 μm to about 300 μm. 
     The transparent light emitting apparatus may include conductive layers configured to electrically connect the LED packages with the wiring electrodes. 
     A pitch of the metal mesh may be 400 μm or less, and a width of the metal mesh may be 7 μm or more. 
     The transparent light emitting apparatus may include a second transparent substrate disposed separately from the first transparent substrate and a filler disposed between the first transparent substrate and the second transparent substrate to cover the LED packages. 
     The wiring sheet may include an interface portion protruding outward from the first transparent substrate and electrically connected to an external power supply, and the interface portion may include electrode patterns electrically connected to the wiring electrodes. 
     The wiring sheet may be manufactured through a roll-to-roll process. 
     The transparent light emitting apparatus may include a quadrangular frame disposed in an edge area of the first transparent substrate and a transparent filler configured to fill the frame to cover the plurality of LED packages. 
     The transparent light emitting apparatus may include a second transparent substrate disposed separately from the first transparent substrate by the frame. 
     According to another aspect of the present invention, there is provided a transparent light emitting apparatus including a wiring sheet including a flexible base layer and a plurality of wiring electrodes formed on the base layer and a plurality of LED packages electrically connected to the wiring electrodes. 
     Each of the wiring electrodes may be made of a conducting wire having a width of from about 2 μm to about 20 μm. 
     Each of the wiring electrodes may include metal mesh. 
     The wiring sheet may include an interface portion protruding from an end of the base layer and electrically connected to an external power supply, and the interface portion may include electrode patterns electrically connected to the wiring electrodes. 
     The transparent light emitting apparatus may include a quadrangular frame disposed in an edge area of the base layer and a transparent filler configured to fill the frame to cover the plurality of LED packages. 
     The transparent light emitting apparatus may include a protective film disposed separately from the base layer. 
     A pitch of the metal mesh may be 400 μm or less, and a width of the metal mesh may be 7 μm or more. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail exemplary embodiments thereof with reference to the accompanying drawings, in which: 
         FIG. 1A  is a view of a transparent light emitting apparatus according to an embodiment of the present invention; 
         FIG. 1B  is illustrates a modification of the coupling relation shown in  FIG. 1A ; 
         FIG. 2  is a top view of a first transparent substrate according to an embodiment of the present invention; 
         FIG. 3A  is an enlarged view illustrating a portion A of  FIG. 2 ; 
         FIG. 3B  illustrates examples of a shape of metal mesh shown in  FIG. 3A ; 
         FIG. 4  is an enlarged view illustrating a portion B of  FIG. 3 ; 
         FIG. 5  is a side view of the transparent light emitting apparatus according to an embodiment of the present invention; 
         FIG. 6  is a schematic cross-sectional view of a transparent light emitting apparatus according to another embodiment of the present invention; 
         FIG. 7  is a view illustrating a configuration in which an interface portion of the transparent light emitting apparatus is electrically connected to a control unit according to another embodiment of the present invention; 
         FIG. 8  is an enlarged view of the interface portion of the transparent light emitting apparatus according to another embodiment of the present invention; and 
         FIG. 9  is a view illustrating a configuration in which the transparent light emitting apparatus is attached to a substrate according to another embodiment of the present invention. 
         FIG. 10  is a schematic cross-sectional view of a transparent light emitting apparatus according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Exemplary embodiments of the present invention will be described in detail below with reference to the accompanying drawings. While the present invention is shown and described in connection with exemplary embodiments thereof, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention. 
     The present invention may have various modifications and several embodiments, and exemplary embodiments thereof are shown in the drawings and will be described in detail. 
     However, the present invention will not be limited to the exemplary embodiments but should be understood as including all modifications, equivalents, and substitutes included in the spirit and the technical scope of the present. 
     In the present specification, terms of “comprise” or “have” are used to designate features, numbers, steps, operations, elements, components or combinations thereof disclosed in the specification as being present but not preclude possibility of the existence or the addition of one or more other features, numbers, steps, operations, elements, components, or combinations thereof. 
     Also, it will be understood that the attached drawings are to be enlarged or reduced for convenience of description. 
     The embodiments of the present invention will be described with reference to the drawings. Throughout the specification, like reference numerals designate like elements and a repetitive description thereof will be omitted. 
       FIG. 1A  is a view of a transparent light emitting apparatus according to an embodiment of the present invention.  FIG. 1B  is illustrates a modification of the coupling relation shown in  FIG. 1A .  FIG. 2  is a top view of a first transparent substrate  30  according to an embodiment of the present invention.  FIG. 3A  is an enlarged view illustrating a portion A of  FIG. 2 , and  FIG. 3B  illustrates examples of a shape of metal mesh shown in  FIG. 3A .  FIG. 4  is an enlarged view illustrating a portion B of  FIG. 3 .  FIG. 5  is a side view of the transparent light emitting apparatus according to an embodiment of the present invention. 
     Referring to  FIG. 1A  and  FIG. 2 , the transparent light emitting apparatus includes the first transparent substrate  30 , a wiring sheet  60  disposed on the first transparent substrate  30 , and a plurality of light emitting diode (LED) packages  40  disposed on the wiring sheet  60 . 
     To the first transparent substrate  30  and a second transparent substrate  10 , all substrates having transparent materials may be applied. As an example, the first transparent substrate  30  and the second transparent substrate  10  may be glass substrates. The first transparent substrate  30  and the second transparent substrate  10  may be manufactured in various sizes according to general standards of glass in building. 
     A transparent filler  20  is disposed between the first transparent substrate  30  and the second substrate  10 , thereby fixing and protecting the plurality of LED packages  40 . As the transparent filler  20 , various types of polymer resin may be selected. 
     The wiring sheet  60  includes a base layer  61  and a plurality of wiring electrodes  50  formed on the base layer  61 . The base layer  61  may be a polymer film formed of one of polyethylene terephthalate (PET), polycarbonate (PC), and polymethyl methacrylate (PMMA). 
     The plurality of wiring electrodes  50  may be one of conducting wires and metal mesh. Here, the wiring electrodes  50  may be transparent electrodes which are not visible to the naked eye at a predetermined distance. When being formed at a width of about 2 to about 20 μm, the conducting wires are not easily visible to the naked eye. To increase transparency, a line width of the conducting wires may be formed to be about 2 to about 10 μm. 
     Also, since being patterned with a width of about several μm or less, the metal mesh are substantially transparent. The wiring electrode  50  may be formed by forming a copper (Cu) layer on the base layer  61  and patterning the Cu layer. That is, it is possible to form conducting wires by pattering as lines of a single line type or to pattern as a mesh shape. Hereinafter, it will be described that the wiring electrode  50  is metal mesh. 
     A thickness of the base layer  61  may be from about 50 μm to about 300 μm. When the thickness is less than 50 μm, it is difficult to maintain full strength while joining the LED packages  40 . When the thickness is more than 300 μm, since transparency decreases, it is difficult to perform a function of the transparent light emitting apparatus. The plurality of wiring electrode  50  may be formed depending on the number of the LED packages  40  and an electrode type. 
     The plurality of LED packages  40  are arranged in a matrix form on the wiring sheet  60 . There is no limitation on the number of the LED packages, and an appropriate number of the LED packages may be arranged to provide text or images. The LED packages  40  individually receive power from a control unit  1  to be driven. 
     Referring to  FIG. 1B , a quadrangular frame  22  may be disposed in an edge area of the base layer  61  of the wiring sheet  60  and the transparent filler  20  may be disposed inside the frame  22 . The frame  22  may be a double-sided tap having a certain thickness. The second transparent substrate  10  may be disposed separately from the first transparent substrate  30  due to the thickness of the frame  22 . 
     However, it is not limited thereto. The frame  22  may be manufactured by forming one or more selected from SiO 2 , Si x O y , Si 3 N 4 , SiN, SiO x N y , AI 2 O 3 , TiO 2 , and AlN on an edge area of one of the base layer  61  and the second transparent substrate  10 . 
     An injection hole is formed on one side of the frame  22 , and the transparent filler  20  may be injected. That is, edges of the first transparent substrate  30  and the second transparent substrate  10  are sealed with the frame  22  and then the transparent filler  20  may be injected through the injection hole. 
     The transparent filler  20  may include a protrusion  21  inserted into the injection hole. That is, the protrusion  21  may protrude outward from a filling area defined by the frame  22 . 
     One injection hole is shown in  FIG. 1B  but may be formed in respective edges. Accordingly, the protrusion may be formed in respective edges. According to a structure described above, a flow of the transparent filler  20  is improved, thereby reducing an unfilled area. 
     Referring to  FIGS. 3A to 4 , each of the LED packages  40  includes a plurality of electrodes  41 . In detail, the LED package  40  may include three drive electrodes  41   b ,  41   c , and  41   d , and one common electrode  41   a . A pitch between the LED packages  40  may be from about 5 mm to about 50 mm. 
     The drive electrodes  41   b ,  41   c , and  41   d  may be anodes, and the common electrode  41   a  may be a cathode. The LED package  40  may be a package formed by modularizing a blue LED chip, a green LED chip, and a red LED chip. 
     In detail, a wiring electrode  51  (hereinafter referred to as a common wiring electrode) connected to the common electrode  41   a  of the LED package  40  and wiring electrodes  52 ,  53 , and  54  (hereinafter referred to as drive wiring electrodes) connected to the drive electrodes  41   b ,  41   c , and  41   d  of the LED package  40  are formed on the base layer  61  of the wiring sheet  60 . 
     Electrode pads  55  are formed on ends of the wiring electrodes  50 , respectively. The electrode pad  55  may be electrically connected to a printed circuit board (PCB) and may apply power to the LED package  40 . 
     For example, when power is applied to a first drive wiring electrode  52  while power is being applied to the common wiring electrode  51 , the LED package  40  may emit blue light. Also, when power is applied to all first to third drive wiring electrodes  52 ,  53 , and  54 , the LED package  40  may emit white light. Accordingly, various colors of light may be emitted by selectively applying power to the first to third drive wiring electrodes  52 ,  53 , and  54 . Also, a color temperature may be adjusted by controlling currents. 
     The common wiring electrode  51  is connected to the common electrodes  41   a  of a plurality of LED packages  40   a  and  40   b  in common. Also, the drive wiring electrodes  52 ,  53 , and  54  are connected to the drive electrodes  41   b ,  41   c , and  41   d  of the LED package  40 , respectively. 
     The common wiring electrode  51 , the drive wiring electrodes  52 ,  53 , and  54 , and the electrode pad  55  may be manufactured as metal mesh M. In detail, a mesh layer is formed on the base layer  61  and then patterned, thereby forming a wiring electrode. 
     General indium tin oxide (ITO) wiring electrodes are formed with a large area to reduce resistance. However, when manufactured using a conducting wire or metal mesh, a thin wiring electrode may be manufactured due to relatively lower resistance. Accordingly, it is of great advantage to manufacture light emitting apparatuses with high resolution. 
     Also, since the wiring electrode is manufactured on the base layer  61  and then stuck to a glass substrate, a manufacturing process becomes simplified. Since a large conducting pattern or mesh pattern may be formed through a roll-to-roll process and a patterning process and may be attached to a glass substrate, it is easy to manufacture a large transparent light emitting apparatus. 
     The metal mesh M has a quadrangular shape in P 1  of  FIG. 3A  but is not limited thereto. As shown in P 2  of  FIG. 3B , the metal mesh M may include consecutively arranged regular hexagons. Alternatively, as shown in P 3  of  FIG. 3B , the metal mesh M may include consecutively arranged hexagons. Although not shown in the drawings, polygons may be consecutively arraigned. 
     According to a structure described above, since contact points of the metal mesh M increase, resistance and a risk of disconnection may be reduced. 
     Table 1 below shows a result of measuring resistance values when metal mesh which has a channel with a width MW 1  of about 790 μm and a length 250 mm varies in thickness, pitch P, and line width MW 2  of the metal mesh. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Thicknesses (□) 
                 Pitches (μm) 
                 Widths (μm) 
                 Resistance value (Ω) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 3000 
                 300 
                 3 
                 2177 
               
               
                   
                   
                 5 
                 1303 
               
               
                   
                   
                 7 
                 929 
               
               
                   
                 400 
                 3 
                 3511 
               
               
                   
                   
                 5 
                 2102 
               
               
                   
                   
                 7 
                 1499 
               
               
                 4000 
                 300 
                 3 
                 1634 
               
               
                   
                   
                 5 
                 977 
               
               
                   
                   
                 7 
                 696 
               
               
                   
                 400 
                 3 
                 2632 
               
               
                   
                   
                 5 
                 1575 
               
               
                   
                   
                 7 
                 954 
               
               
                 5000 
                 300 
                 3 
                 1633 
               
               
                   
                   
                 5 
                 781 
               
               
                   
                   
                 7 
                 557 
               
               
                   
                 400 
                 3 
                 2105 
               
               
                   
                   
                 5 
                 1261 
               
               
                   
                   
                 7 
                 899 
               
               
                   
               
            
           
         
       
     
     To allow optical power of the plurality of LED packages  40  to be uniform, it is necessary that resistance of a wiring electrode is 1 kΩ or less. Referring to Table 1, it can be known that although a thickness varies, a resistance value is 1 kΩ or less when a pitch is 400 μm or less and a width is 7 μm or more. 
     Accordingly, since resistance is not more than 1 kΩ when it is satisfied that the pitch of the metal mesh M is 400 μm or less and the width is 7 μm or more, although the thickness of the metal mesh varies, it is possible to uniformly control the optical power of the plurality of LED packages  40 . Here, for transparency, the line width of the metal mesh may be 20 μm or less. 
     Also, when the pitch of the metal mesh M is from about 300 μm to about 400 μm and the width is from about 10 μm to about 20 μm, although a length of the wiring electrode becomes longer, it is possible to uniformly control the optical power of the plurality of LED packages  40 . 
     Referring to  FIG. 5 , the electrode  41  of the LED package  40  may be electrically connected to the wiring electrode  50  through a silver paste S that is a conductive layer. Since the transparent filler  20  is disposed between the first transparent substrate  30  and the second substrate  10 , it is possible to firmly fix the LED package  40 . 
     According to one embodiment of the present invention, since the wiring electrode  50  is formed on the base layer  61 , there is provided a higher level of adhesion than that of directly forming a wiring electrode on a glass substrate. Also, the thickness of the base layer  61  is from about 50 μm to about 300 μm, it is possible to maintain full transparency. 
     Since a general ITO has high thermal resistance, a silver paste is applied onto the ITO and the silver paste and an electrode of an LED package are electrically connected through soldering. 
     However, according to one embodiment of the present invention, the wiring electrode  50  has low thermal resistance because it is metal, it is possible to provide an electrical connection with the electrode  41  of the LED package  40  only using a silver paste. Accordingly, additional soldering may be omitted. 
     Since a curing temperature of the silver paste is relatively low, the base layer  61  is not melted. Accordingly, a conductive layer which connects an LED package with a wiring electrode contains silver. According to one embodiment of the present invention, since a soldering process which is performed at a high temperature may be omitted using a metal as a wiring electrode, it is possible to manufacture a large wiring sheet using a base layer. If necessary, an additional buffer layer may be further formed on the wiring electrode  50 . 
       FIG. 6  is a schematic cross-sectional view of a transparent light emitting apparatus according to another embodiment of the present invention.  FIG. 7  is a view illustrating a configuration in which an interface portion  62  of the transparent light emitting apparatus is electrically connected to a control unit  1  according to another embodiment of the present invention.  FIG. 8  is an enlarged view of the interface portion  62  of the transparent light emitting apparatus according to another embodiment of the present invention.  FIG. 9  is a view illustrating a configuration in which the transparent light emitting apparatus is attached to a substrate  30  according to another embodiment of the present invention. 
     Referring to  FIG. 6 , the transparent light emitting apparatus according to another embodiment of the present invention includes a wiring sheet  60  which includes a plurality of wiring electrodes  50  formed on a flexible base layer  61 , a plurality of LED packages  40  electrically connected to the wiring electrodes  50  through a silver paste S, a protective film  71  disposed separately from the wiring sheet  60 , and a filler  72  disposed between the protective film  71  and the wiring sheet  60 . 
     According to the configuration described above, the base layer  61  and the protective film  71  perform as a substrate instead of a transparent substrate, thereby manufacturing a flexible transparent light emitting apparatus. 
     A thickness of the base layer  61  may be from about 50 μm to about 300 μm. When the thickness is less than 50 μm, it is impossible to maintain full strength and it is difficult to fully support the joining of the LED package  40 . When the thickness is more than 300 μm, since transparency decreases, it is difficult to perform a function of the transparent light emitting apparatus. 
     Since the base layer  61  has relatively lower strength than a glass substrate, it is possible to maintain necessary strength by providing a full thickness of the filler  72 . As an example, when the filler  72  has a thickness of from about 1.0 to about 2.0 times of a thickness of the LED package  40 , the necessary strength may be provided. 
     As described with reference to  FIG. 1B , a frame may be formed on the base layer  61  and the filler  72  may be injected into a filling area defined by the frame. That is, the configuration of the frame and the filler described above may be applied without change except that a flexible substrate is used. The protective film  71  may be disposed separately from the base layer  61  as far as a thickness of the frame. The protective film  71  may be one of all substantially transparent films. 
     Since detailed configurations of the wiring sheet  60  and the LED package  40  are identical to the described above, a repetitive description thereof will be omitted and particular features will be described in detail. 
     Referring to  FIGS. 7 and 8 , the wiring sheet  60  includes a plurality of interface portions  62  which protrude from an end of the base layer  61  and are electrically connected to an external power supply. 
     The interface portion  62  includes an electrode pattern  62   a  electrically connected to the wiring electrode  50  and a pad  62   b . The electrode pattern  62   a  and the pad  62   b  may be metal mesh M identical to the wiring electrode  50 . 
     The transparent light emitting apparatus may be divided into an active area W 1  which outputs images to be displayed and an inactive area W 2 . The interface portions  62  are disposed in the inactive area W 2 . 
     The interface portions  62  may be manufactured by forming the wiring electrode  50 , the electrode pattern  62   a , and the pad  62   b  by patterning a mesh layer formed on the base layer  61  and cutting an area in which the electrode pattern  62   a  is not formed. 
     The interface portion  62  may be directly connected to a connector  1   a  of the control unit  1  and may apply power to the wiring electrode  50 . Accordingly, it is possible to omit an additional PCB. 
     Referring to  FIG. 6 , an adhesive layer  73  and a cover layer  74  may be formed on the other surface of the base layer  61 . Accordingly, the cover layer  74  may be detached and the transparent light emitting apparatus may be attached to a desirable substrate  30  as shown in  FIG. 9 . 
     As described above, because the transparent light emitting apparatus is flexible, it may be attached anywhere on a curved substrate to display images. 
     For example, in an embodiment of the present invention, a configuration of interface portions may be added. In this case, the interface portions may protrude outward from a first transparent substrate and may be electrically connected to a control unit. 
     According to one embodiment of the present invention, a conducting wire or metal mesh is used instead of indium tin oxide (ITO), thereby reducing manufacturing costs and manufacturing a large light emitting apparatus. 
     Also, since a base layer is used as a substrate instead of a glass substrate, it is possible to manufacture a flexible transparent light emitting apparatus. 
       FIG. 10  is a schematic cross-sectional view of a transparent light emitting apparatus according to another embodiment of the present invention. 
     Referring to  FIG. 10 , the transparent light emitting apparatus according to another embodiment of the present invention includes a wiring sheet  60  which includes a plurality of wiring electrodes  50  formed on a flexible base layer  61 , a plurality of LED packages  40  electrically connected to the wiring electrodes  50 , a protective film  71  disposed separately from the wiring sheet  60 , and an optical adhesive  75  disposed between the protective film  71  and the wiring sheet  60 . 
     The protective film  71  and the optical adhesive  75  have a plurality of holes in which the plurality of LED packages  40  are inserted. Thus, the plurality of LED packages  40  may be exposed towards the exterior of the protective film  71 . The optical adhesive  75  may be a pressure sensitive adhesive (PSA) or an optical clearance adhesive (OCA). 
     A non-conductive material  77  is injected in a space between the plurality of holes and the plurality of LED packages  40  to protect the plurality of LED packages  40  and the plurality of wiring electrodes  50 . As the non-conductive material, various types of polymer resin may be selected. 
     According to the configuration described above, it is possible to omit a process in which a filler is injected between the protective film  71  and the wiring sheet  60  so that the manufacturing process of the transparent light emitting apparatus becomes simplified. 
     It will be apparent to those skilled in the art that various modifications can be made to the above-described exemplary embodiments of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention covers all such modifications provided they come within the scope of the appended claims and their equivalents.