Patent Publication Number: US-8115369-B2

Title: Lighting device

Description:
The present application claims priority under 35 U.S.C. §119(e) of Korean Patent Applications Nos. 10-2009-0107498 filed on Nov. 9, 2009 and 10-2010-0032063 filed on Apr. 7, 2010, which is hereby incorporated by reference in its entirety. 
     BACKGROUND 
     1. Field 
     This embodiment relates to a lighting device. 
     2. Description of the Related Art 
     A light emitting diode (LED) is a semiconductor element for converting electric energy into light. The LED has advantages of low power consumption, a semi-permanent span of life, a rapid response speed, safety and an environment-friendliness. Therefore, many researches are devoted to substitution of the existing light sources with the LED. The LED is now being increasingly used as a light source for lighting devices, for example, various lamps used interiorly and exteriorly, a liquid crystal display device, an electric sign and a street lamp and the like. 
     SUMMARY 
     One embodiment is a lighting device. The lighting device includes: 
     a substrate; 
     a light emitting device disposed on the substrate; 
     a heat radiating body radiating heat from the light emitting device; and 
     a pad being interposed between the substrate and the heat radiating body and transferring heat generated from the light emitting device to the heat radiating body and comprising silicon of 10 to 30 wt %, a filler of 70 to 90 wt %, glass fiber of 2 to 7 wt % in terms of weight percent (wt %). 
     Another embodiment is a lighting device. The lighting device includes: 
     a substrate; 
     a light emitting device disposed on the substrate; 
     a heat radiating body radiating heat from the light emitting device; and 
     a pad being interposed between the substrate and the heat radiating body and comprising a plurality of layers. 
     Further another embodiment is a lighting device. The lighting device includes: 
     a light emitting module substrate including a plurality of light emitting devices; 
     a pad being disposed on one side of the light emitting module substrate and including a plurality of layers; 
     a heat radiating body including a receiving groove for receiving the pad and the light emitting module substrate so that one side of the heat radiating body contacts with the pad and the light emitting module substrate; 
     an outer case being spaced apart at a predetermined interval from the outer surface of the heat radiating body and surrounding the heat radiating body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a bottom perspective view of a lighting device according to an embodiment of the present invention. 
         FIG. 2  is a top perspective view of the lighting device of  FIG. 1 . 
         FIG. 3  is an exploded perspective view of the lighting device of  FIG. 1 . 
         FIG. 4  is a cross sectional view of the lighting device of  FIG. 1 . 
         FIG. 5  is a perspective view of a heat radiating body of the lighting device of  FIG. 1 . 
         FIG. 6  is a cross sectional view taken along a line A-A′ of  FIG. 5 . 
         FIG. 7  is a perspective view showing coupling of a light emitting module substrate and a first protection ring of the lighting device of  FIG. 1 . 
         FIG. 8  is a cross sectional view taken along a line B-B′ of  FIG. 7 . 
         FIG. 9  is a view for describing a structure of a thermal pad. 
         FIG. 10  is a perspective view of a guide member of the lighting device of  FIG. 1 . 
         FIG. 11  is a plan view of the guide member of  FIG. 10 . 
         FIG. 12  is a cross sectional view showing an enlarged lower part of the lighting device of  FIG. 1 . 
         FIG. 13  is a bottom view of the lighting device of  FIG. 1 . 
         FIG. 14  is a top view of the lighting device of  FIG. 1 . 
         FIG. 15  is a perspective view of a guide member of a lighting device according to another embodiment. 
         FIG. 16  is a perspective view of an inner case of the lighting device of  FIG. 1 . 
         FIG. 17  is a view showing a heat radiating body of the lighting device according to the another embodiment. 
         FIG. 18  is a perspective view of an outer case of the lighting device of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, an embodiment will be described in detail with reference to the accompanying drawings. 
     It will be understood that when an element is referred to as being ‘on’ or “under” another element, it can be directly on/under the element, and one or more intervening elements may also be present. 
       FIG. 1  is a bottom perspective view of a lighting device  1  according to an embodiment of the present invention.  FIG. 2  is a top perspective view of the lighting device  1 .  FIG. 3  is an exploded perspective view of the lighting device  1 .  FIG. 4  is a cross sectional view of the lighting device  1 . 
     Referring to  FIGS. 1 to 4 , the lighting device  1  includes an inner case  170  of which the upper part includes a connection terminal  175  and of which the lower part includes an insertion unit  174 , a heat radiating body  150  including a first receiving groove  151  into which the insertion unit  174  of the inner case  170  is inserted, a light emitting module substrate  130  emitting light onto a bottom surface of the heat radiating body  150  and including one or a plurality of light emitting devices  131 , a guide member  100  being coupled to the circumference of the lower part of the heat radiating body  150  and strongly fixing the light emitting module substrate  130  to the heat radiating body  150 , and an outer case  180  outside the heat radiating body  150 . 
     The heat radiating body  150  includes receiving grooves  151  and  152  on both sides thereof and receives the light emitting module substrate  130  and a driving unit  160 . The heat radiating body  150  functions to radiate heat generated from the light emitting module substrate  130  or/and the driving unit  160 . 
     Specifically, as shown in  FIGS. 3 and 4 , the first receiving groove  151  in which the driving unit  160  is disposed is formed on a top surface of the heat radiating body  150 . A second receiving groove  152  in which the light emitting module substrate  130  is disposed is formed on the bottom surface of the heat radiating body  150 . 
     An outer surface of the heat radiating body  150  has a prominence and depression structure. The prominence and depression structure causes the surface area of the heat radiating body  150  to be increased, improving heat radiation efficiency. The heat radiating body  150  is made of a metallic material or a resin material which has excellent heat radiation efficiency. However, there is no limit to the material of the heat radiating body  150 . For example, the material of the heat radiating body  150  may include at least one of Al, Ni, Cu, Ag, Sn and Mg. 
     The light emitting module substrate  130  is disposed in the second receiving groove  152  formed on the bottom surface of the heat radiating body  150 . The light emitting module substrate  130  includes a substrate  132  and either one or a plurality of the light emitting devices  131  disposed on the substrate  132 . A plurality of the light emitting devices may be disposed in a radial shape based on a central axis of the substrate  132 . 
     The one or each of the plurality of the light emitting devices  131  includes at least one light emitting diode (hereinafter, referred to as LED). The LEDs include red, green, blue and white LEDs, each of which emits red, green, blue and white lights respectively. The number and kind of the LED are not limited to this. 
     The light emitting module substrate  130  is electrically connected to the driving unit  160  by a wiring, etc., via a through-hole  153  passing through a basal surface of the heat radiating body  150 . Therefore, the light emitting module substrate  130  can be driven by receiving electric power. 
     Here, a second protection ring  155  is formed in the through-hole  153 , second protection ring  155  second protection ring  155 . Therefore, it is possible to prevent moisture and impurities from penetrating between the light emitting module substrate  130  and the heat radiating body  150 , to improve a withstand voltage characteristic of the lighting device, and to prevent an electrical short-circuit, EMI, EMS and so on caused by contact of the wiring with heat radiating body  150  second protection ring  155   
     A thermal pad  140  is attached to a bottom surface of the light emitting module substrate  130 . The thermal pad  140  is attached to the second receiving groove  152 . Otherwise, the light emitting module substrate  130  and the thermal pad  140  may be also integrally formed. The thermal pad  140  allows heat generated from the light emitting module substrate  130  to be more effectively transferred to the heat radiating body  150 . 
     The light emitting module substrate  130  is securely fixed to the second receiving groove  152  by the guide member  100 . The guide member  100  includes an opening  101  for exposing the one or a plurality of the light emitting devices  131  mounted on the light emitting module substrate  130 . The guide member  100  can fix the light emitting module substrate  130  by pressing an outer circumferential surface of the light emitting module substrate  130  to the second receiving groove  152  of the heat radiating body  150 . 
     The guide member  100  also includes an air flow structure for allowing air to flow between the heat radiating body  150  and the outer case  180  and maximizes heat radiation efficiency of the lighting device  1 . The air flow structure may correspond to, for example, a plurality of first heat radiating holes  102  formed between an inner surface and an outer surface of the guide member  100 , or a prominence and depression structure formed on the inner surface of the guide member  100 . The air flow structure will be described later in detail. 
     At least one of a lens  110  and a first protection ring  120  may be included between the guide member  100  and the light emitting module substrate  130 . 
     The lens  110  includes various shapes like a convex lens, a concave lens, a parabola-shaped lens and a fresnel lens, etc., so that the distribution of light emitted from the light emitting module substrate  130  can be controlled as desired. The lens  110  includes a fluorescent material and is used to change the wavelength of light. The lens  110  is used without being limited to this. 
     The first protection ring  120  not only prevents moisture and impurities from penetrating between the guide member  100  and the light emitting module substrate  130  but also leaves a space between an outer surface of the light emitting module substrate  130  and an inner surface of the heat radiating body  150 , so that the light emitting module substrate  130  is prevented from contacting directly with the heat radiating body  150 . As a result, it is possible to improve a withstand voltage characteristic of the lighting device  1  and to prevent EMI, EMS and the like of the lighting device  1 . 
     As shown in  FIGS. 3 and 4 , the inner case  170  includes the insertion unit  174  and the connection terminal  175 . The insertion unit  174  is formed in the lower part of the inner case  170  and is inserted into the first receiving groove  151  of the heat radiating body  150 . The connection terminal  175  is formed in the upper part of the inner case  170  and is electrically connected to an external power supply. 
     A side wall of the insertion unit  174  is disposed between the driving unit  160  and the heat radiating body  150 , and prevents an electrical short-circuit between them. Accordingly, it is possible to improve a withstand voltage characteristic of the lighting device  1  and to prevent EMI, EMS and the like of the lighting device  1 . 
     The connection terminal  175  is inserted into an external power supply having a socket shape so that electric power can be supplied to the lighting device  1 . However, the shape of the connection terminal  175  can be variously changed according to the design of the lighting device  1  without being limited to this. 
     The driving unit  160  is disposed in the first receiving groove  151  of the heat radiating body  150 . The driving unit  160  includes a converter converting an alternating current supplied from an external power supply into a direct current, a driving chip controlling to drive the light emitting module substrate  130 , an electrostatic discharge (ESD) protective device protecting the light emitting module substrate  130 . The driving unit  160  is not limited to include other components. 
     The outer case  180  is coupled to the inner case  170 , receives the heat radiating body  150 , the light emitting module substrate  130  and the driving unit  160 , and forms an external appearance of the lighting device  1 . 
     While the outer case  180  has a circular section, the outer case  180  can be designed to have a polygon section or elliptical section and so on. There is no limit to the cross section shape of the outer case  180 . 
     Since the heat radiating body  150  is not exposed by the outer case  180 , it is possible to prevent a burn accident and an electric shock and to make it easier to handle the lighting device  1 . 
     Hereinafter, the following detailed description will be focused on each component of the lighting device  1  according to the embodiment. 
     Heat Radiating Body  150   
       FIG. 5  is a perspective view of the heat radiating body  150 .  FIG. 6  is a cross sectional view taken along a line A-A′ of  FIG. 5 . 
     Referring to  FIGS. 4 to 6 , the first receiving groove  151  in which the driving unit  160  is disposed is formed on a first side of the heat radiating body  150 . The second receiving groove  152  in which the light emitting module substrate  130  is disposed is formed on a second side opposite to the first side. Widths and depths of the first and the second receiving grooves  151  and  152  are changeable depending on the widths and thicknesses of the driving unit  160  and light emitting module substrate  130 . 
     The heat radiating body  150  is made of a metallic material or a resin material which has excellent heat radiation efficiency. However, there is no limit to the material of the heat radiating body  150 . For example, For example, the material of the heat radiating body  150  may include at least one of Al, Ni, Cu, Ag, Sn and Mg. 
     The outer surface of the heat radiating body  150  has a prominence and depression structure. The prominence and depression structure causes the surface area of the heat radiating body  150  to be increased, improving heat radiation efficiency. As shown, the prominence and depression structure may include a wave-shaped prominence curved in one direction. However, there is no limit to the shape of the prominence and depression. 
     The through-hole  153  is formed on the basal surface of the heat radiating body  150 . The light emitting module substrate  130  and the driving unit  160  are electrically connected to each other by a wiring. 
     Here, the second protection ring  155  is coupled to the through-hole  153  so that it is possible to prevent moisture and impurities from penetrating through the through-hole  153  and to prevent an electrical short-circuit, etc., caused by contact of the wiring with heat radiating body  150 . The second protection ring  155  is formed of a rubber material, a silicon material or other electrical insulating material. 
     A first fastening member  154  is formed on a side of the lower part of the heat radiating body  150  in order to strongly couple the guide member  100  to the heat radiating body  150 . The first fastening member  154  includes a hole into which a screw is inserted. The screw can strongly couple the guide member  100  to the heat radiating body  150 . 
     In addition, so as to easily couple the guide member  100 , a first width P 1  of the lower part of the heat radiating body  150  to which the guide member  100  is coupled is less than a second width P 2  of another part of the heat radiating body  150 . However, there is no limit to the widths of the heat radiating body  150 . 
     Light Emitting Module Substrate  130 , Thermal Pad  140  and First Protection Ring  120   
       FIG. 7  is a perspective view showing coupling of the light emitting module substrate  130  and the first protection ring  120 .  FIG. 8  is a cross sectional view taken along a line B-B′ of  FIG. 7 . 
     Referring to  FIGS. 3 ,  7  and  8 , the light emitting module substrate  130  is disposed in the second receiving groove  152 . The first protection ring  120  is coupled to the circumference of the light emitting module substrate  130 . 
     The light emitting module substrate  130  includes the substrate  132  and one or a plurality of the plurality of the light emitting devices  131  mounted on the substrate  132 . 
     The substrate  132  is made by printing a circuit pattern on an insulator. For example, a common printed circuit board (PCB), a metal core PCB, a flexible PCB and a ceramic PCB and the like can be used as the substrate  132 . 
     The substrate  132  is made of a material capable of efficiently reflecting light. White and silver colors, etc., capable of efficiently reflecting light is formed on the surface of the substrate  132 . 
     The one or a plurality of the light emitting devices  131  are mounted on the substrate  132 . Each of a plurality of the light emitting devices  131  includes at least one light emitting diode (LED). The LEDs include various colors such as red, green, blue and white, each of which emits red, green, blue and white lights respectively. The number and kind of the LED are not limited to this. 
     Meanwhile, there is no limit in disposing one or more light emitting devices  131 . However, in the embodiment, while the wiring is formed under the light emitting module substrate  130 , the light emitting device is not necessarily mounted on an area of the light emitting module substrate  130 , which corresponds to an area in which the wiring has been formed. For example, as shown, when the wiring is formed in the middle area of the light emitting module substrate  130 , the light emitting device is not necessarily mounted on the middle area. In this case, the thermal pad may be disposed on the light emitting module substrate in correspondence with an area in which the light emitting device is disposed. Preferably, a central part of the thermal pad may be open. 
     The thermal pad  140  is attached to the lower surface of the light emitting module substrate  130 . The thermal pad  140  is made of a material having a high thermal conductivity such as a thermal conduction silicon pad or a thermal conduction tape and the like. The thermal pad  140  can effectively transfer heat generated by the light emitting module substrate  130  to the heat radiating body  150 . Here, in order to increase heat radiating effect, an area of the thermal pad is required to be at least larger than that of the light emitting module substrate. 
     Such a thermal pad  140  includes silicon, a filler and glass fiber. More preferably, it is desired that the thermal pad  140  is formed by adding a catalyst to the said three materials. 
     More specifically, in terms of weight percent (wt %), the thermal pad  140  is required to include silicon of 10 to 30 wt %, a filler of 70 to 90 wt %, glass fiber of 2 to 7 wt % and a catalyst of 0.3 to 1.5 wt %. 
     The silicon contributes to insulation and viscosity of the thermal pad  140 . If the weight percent of the silicon is less than 10 wt %, the insulation and viscosity of the thermal pad  140  is reduced. If the weight percent of the silicon is greater than 30 wt %, the insulation is excessively increased. As a result, thermal conductivity is reduced. 
     The filler contributes to thermal conductivity and hardness of the thermal pad  140 . If the weight percent of the filler is less than 70 wt %, thermal conductivity is reduced so that the thermal pad  140  cannot perform a function of its own, and hardness is reduced so that it is hard to change a shape of the thermal pad  140  into a particular shape. If the weight percent of the filler is greater than 90 wt %, thermal conductivity and hardness are excessively increased, so that errors such as a crack of the thermal pad  140 , etc., are generated. Here, the filler is required to be aluminum oxide (alumina). 
     The glass fiber contributes to hardness of the thermal pad  140 . If the weight percent of the glass fiber is less than 2 wt %, hardness is reduced so that the thermal pad  140  is torn and an adhesive strength between the thermal pad  140  and the silicon is reduced. If the weight percent of the glass fiber is greater than 7 wt %, ductility is lost so that errors may be generated. 
     As the most exemplary embodiment of the thermal pad  140 , in terms of weight percent (wt %), silicon of 16 wt %, aluminum oxide of 80 wt %, glass of 3.5 wt % and platinum of 0.5 wt % are required. 
       FIG. 9  is a view for describing a structure of a thermal pad  140 . An embodiment of the thermal pad  140  is shown in (a) of  FIG. 9 . Another embodiment of the thermal pad  140  is shown in (b) of  FIG. 9 . 
     Referring to  FIG. 9 , the thermal pad  140  includes a plurality of layers. For example, the thermal pad  140  includes a silicon mixed layer  910  including silicon and a filler, and a fiber layer  920  including glass fiber. As a concrete form of the thermal pad  140 , as shown in (a) of  FIG. 9 , one side of the silicon mixed layer  910  is adhered to one side of the fiber layer  920 . Also, as shown in (b) of  FIG. 9 , the fiber layer  920  is included within the silicon mixed layer  910 . 
     An adhesive agent is applied on one side of the silicon mixed layer  910  of the thermal pad  140 , thereby more increasing adhesive strength to the heat radiating body  150  or the light emitting module substrate  130 . Specifically, in (a) of  FIG. 9 , an adhesive agent is applied on an upper side of the silicon mixed layer  910 , that is, a side with which the fiber layer  920  does not contact. In (b) of  FIG. 9 , an adhesive agent is applied on one side or both sides of the silicon mixed layer  910 . 
     In case of the lighting device  1  of 3.5 watts to 8 watts, the thickness of the thermal pad  140  is required to be from 0.4 T to 0.7 T. In case of the lighting device  1  of 15 watts, the thickness of the thermal pad  140  is required to be from 0.7 T to 1.0 T. Here, “T” is a thickness unit. 1T corresponds to 1 mm. 
     The following table 1 shows a withstand voltage characteristic according to the thickness of the thermal pad  140  in case of the lighting device  1  of 3.5 watts to 8 watts. The following table 2 shows a withstand voltage characteristic according to the thickness of the thermal pad  140  in case of the lighting device  1  of 15 watts. Here, the withstand voltage characteristic shows whether a lighting standard is satisfied or not. When a high voltage and a high current are applied to the heat radiating body  150  and the light emitting module substrate  130 , the withstand voltage characteristic shows whether the heat radiating body  150  and the light emitting module substrate  130  penetrate the thermal pad  140  and are short-circuited. An experiment regarding the following tables 1 and 2 is performed by applying a maximum voltage of 5 KV and a maximum current of 100 mA in accordance with Korean withstand voltage acceptance criteria. 
     The following table 1 shows experimental results when the size of the thermal pad  140  is 45φ, the size of the light emitting module substrate  130  is 43φ, and the size of the through-hole  153  of the heat radiating body  150  is 15φ. 
     
       
         
           
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Thickness of the thermal pad 140 
                 PASS or FAIL of a withstand voltage 
               
               
                   
               
             
            
               
                 0.25 T  
                 In case of the lighting device of 5 
               
               
                   
                 watts, FAIL at 2.5 KV 
               
               
                   
                 In case of the lighting device of 8 
               
               
                   
                 watts, FAIL at 4.0 KV 
               
               
                 0.4 T 
                 PASS 
               
               
                 0.7 T 
                 PASS 
               
               
                   
               
            
           
         
       
     
     The following table 2 shows experimental results when the size of the thermal pad  140  is 70φ, the size of the light emitting module substrate  130  is 69φ, and the size of the through-hole  153  of the heat radiating body  150  is 15φ. 
     
       
         
           
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Thickness of the thermal pad 140 
                 PASS or FAIL of a withstand voltage 
               
               
                   
               
             
            
               
                 0.25 T  
                 FAIL 
               
               
                 0.4 T 
                 FAIL at 2.0 KV 
               
               
                 0.7 T 
                 PASS 
               
               
                   
               
            
           
         
       
     
     In table 1, in case of the lighting device of 3.5 watts to 8 watts, the thickness of the thermal pad  140  is required to be less than 0.7 T. This is because, when the thickness of the thermal pad  140  is greater than 0.7 T, heat radiating characteristic is deteriorated and production cost is high while the withstand voltage characteristic is improved. 
     In table 2, in case of the lighting device of 15 watts, the thickness of thermal pad  140  is required to be less than 1.0 T. This is because, when the thickness of the thermal pad  140  is greater than 1.0 T, heat radiating characteristic is deteriorated and production cost is high while the withstand voltage characteristic is improved. 
     The following table 3 shows a withstand voltage characteristic according to the thickness of the thermal pad  140  in case of the lighting device  1  of 5 watts and 8 watts. The following table 4 shows a withstand voltage characteristic according to the thickness of the thermal pad  140  in case of the lighting device  1  of 15 watts. 
     The following table 3 shows experimental results when the size of the thermal pad  140  is 52φ, and the size of the through-hole  153  of the heat radiating body  150  is 15φ. 
     
       
         
           
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                 Thickness of the thermal pad 140 
                 PASS or FAIL of a withstand voltage 
               
               
                   
               
             
            
               
                 0.25 T  
                 In case of the lighting device of 5 
               
               
                   
                 watts and 8 watts, 
               
               
                   
                 FAIL at 3.7 KV 
               
               
                 0.5 T 
                 In case of the lighting device of 5 
               
               
                   
                 watts, PASS at 4.0 KV 
               
               
                   
                 In case of the lighting device of 8 
               
               
                   
                 watts, FAIL at 3.9 KV 
               
               
                 0.7 T 
                 In case of the lighting device of 8 
               
               
                   
                 watts, PASS at 4.0 KV 
               
               
                   
               
            
           
         
       
     
     The following table 4 shows experimental results when the size of the thermal pad  140  is 74φ, and the size of the through-hole  153  of the heat radiating body  150  is 15φ. 
     
       
         
           
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                 Thickness of the thermal pad 140 
                 PASS or FAIL of a withstand voltage 
               
               
                   
               
             
            
               
                 0.25 T  
                 FAIL at 1.5 KV 
               
               
                 0.5 T 
                 FAIL at 2.0 KV 
               
               
                 0.7 T 
                 PASS at 4.0 KV 
               
               
                   
               
            
           
         
       
     
     The first protection ring  120  is formed of a rubber material, a silicon material or other electrical insulating material. The first protection ring  120  is formed in the circumference of the light emitting module substrate  130 . More specifically, as shown, the first protection ring  120  includes a step difference  121  in an inner lower end thereof. The lateral surface of the light emitting module substrate  130  and the circumference of the top surface of the light emitting module substrate  130  come in contact with the step difference  121  of the inner lower end of the first protection ring  120 . An area contacting with the step difference  121  is not limited to this. Additionally, an inner upper end of the first protection ring  120  may includes an inclination  122  in order to improve the light distribution of the light emitting module substrate  130 . 
     The first protection ring  120  not only prevents moisture and impurities from penetrating between the guide member  100  and the light emitting module substrate  130  but also prevents the lateral surface of the light emitting module substrate  130  from directly contacting with the heat radiating body  150 . As a result, it is possible to improve a withstand voltage characteristic of the lighting device  1  and to prevent EMI, EMS and the like of the lighting device  1 . 
     The first protection ring  120  strongly fixes and protects the light emitting module substrate  130 , improving the reliability of the lighting device  1 . 
     Referring to  FIG. 12 , when the lens  110  is disposed on the first protection ring  120 , the first protection ring  120  allows the lens  110  to be disposed apart from the light emitting module substrate  130  by a first distance “h”. As a result, it is much easier to control the light distribution of the lighting device  1 . 
     Guide Member  100   
       FIG. 10  is a perspective view of a guide member  100 .  FIG. 11  is a plan view of the guide member of  FIG. 14 . 
     Referring to  FIGS. 4 ,  10  and  11 , the guide member  100  includes an opening  101  for exposing the light emitting module substrate  130 , a plurality of heat radiating holes  102  between the inside and the outside of the guide member  100 , and a locking groove  103  coupled to the heat radiating body  150 . 
     While the guide member  100  is shown in the form of a circular ring, the guide member  100  can have also shapes such as a polygon and an elliptical ring. There is no limit to the shape of the guide member  100 . 
     The one or a plurality of the light emitting devices  131  of the light emitting module substrate  130  are exposed through the opening  101 . Since the guide member  100  presses the light emitting module substrate  130  to the second receiving groove  152 , the width of the opening  101  is required to be less than that of the light emitting module substrate  130 . 
     More specifically, as the guide member  100  is coupled to the heat radiating body  150 , the guide member  100  give a pressure to the lens  110 , the first protection ring  120  and the circumference of the light emitting module substrate  130 . Accordingly, the lens  110 , the first protection ring  120  and the light emitting module substrate  130  can be securely fixed to the second receiving groove  152  of the heat radiating body  150 , thereby improving the reliability of the lighting device  1 . 
     The guide member  100  can be coupled to the heat radiating body  150  through the locking groove  103 . For example, as shown in  FIG. 4 , a hole of the first fastening member  154  of the heat radiating body  150  is in a line with the locking groove  103  of the guide member  100 . Then, the guide member  100  is coupled to the heat radiating body  150  by inserting a screw into the hole of the first fastening member  154  and the locking groove  103 . However, there is no limit to the method for coupling the guide member  100  to the heat radiating body  150 . 
     Meanwhile, when internal parts such as the driving unit  160  and the light emitting module substrate  130  and the like of the lighting device  1  are required to be changed, the guide member  100  is easily separated from the heat radiating body  150 . Therefore, users can perform maintenance for the lighting device  1  without difficulty. 
     The plurality of the first heat radiating holes  102  are formed between the inside of the outside of the guide member  100 . The plurality of the first heat radiating holes  102  allows air inside the lighting device  1  to smoothly flow, thereby maximizing heat radiation efficiency. Hereinafter, a description thereof will be provided. 
       FIG. 12  is a cross sectional view showing an enlarged lower part of the lighting device  1  according to the embodiment.  FIG. 13  is a bottom view of the lighting device  1 .  FIG. 14  is a top view of the lighting device  1 . 
     Referring to  FIGS. 12 to 14 , the outer case  180  is spaced apart at a predetermined interval from the heat radiating body  150  and surrounds the outer surface of the heat radiating body  150 . An air flow path is hereby created. Air which has flown into the inside of the lighting device  1  through the plurality of the first heat radiating holes  102  formed in the guide member  100  flows along the air flow path and induces the heat radiating body to radiate heat. Specifically, the air which has flown into the lighting device flows to a prominence “a” and depression “b” of the lateral surface of the heat radiating body  150 . Based on a principle of air convection, the air heated by passing through the prominence and depression structure of the heat radiating body  150  can flow out through a plurality of ventilating holes  182  formed between the inner case  170  and the outer case  180 . Otherwise, air flown into the plurality of the ventilating holes  182  may flow out through the plurality of the first heat radiating holes  102 . Air can flow out in various ways without being limited to this. 
     In other words, it is possible to radiate heat by using the principle of air convection through the plurality of the first heat radiating holes  102  and the plurality of the ventilating holes  182 , thereby maximizing heat radiation efficiency. Hereinafter, a description thereof will be provided. 
     Meanwhile, the air flow structure of the guide member  100  is not limited to this and can be changed variously. For example, as shown in  FIG. 15 , a guide member  100 A according to another embodiment has a prominence and depression structure in the inner surface thereof, so that air can flow into the inside of the lighting device through a depression  102 A. 
     Lens  110   
     Referring to  FIGS. 4 and 12 , the lens  110  is formed under the light emitting module substrate  130  and controls the distribution of light emitted from the light emitting module substrate  130 . 
     The lens  110  has various shapes. For example, the lens  110  includes at least one of a parabola-shaped lens, a fresnel lens, a convex lens or a concave lens. 
     The lens  110  is disposed under the light emitting module substrate  130  and spaced apart from the light emitting module substrate  130  by a first distance “h”. The first distance “h” is greater than 0 mm and equal to or less than 50 mm in accordance with the design of the lighting device  1 . 
     The distance “h” is maintained by the first protection ring  120  disposed between the light emitting module substrate  130  and the lens  110 . Otherwise, if another support for supporting the lens  110  is provided in the second receiving groove  152  of the heat radiating body  150 , the distance “h” is maintained between the light emitting module substrate  130  and the lens  110 . There is no limit to the method for maintaining the distance “h”. 
     The lens  110  is fixed by the guide member  110 . The inner surface of the guide member  100  contacts with the lens  110 . The lens  110  and the light emitting module substrate  130  are pressed and fixed to the second receiving groove  152  of the heat radiating body  150  by the inner surface of the guide member  100 . 
     The lens  110  is made of glass, polymethylmethacrylate (PMMA) and polycarbonate (PC) and so on. 
     According to the design of the lighting device  1 , the lens  110  includes fluorescent material. Otherwise, a photo luminescent film (PLF) including the fluorescent material is attached to a light incident surface or a light emitting surface of the lens  110 . Light emitted from the light emitting module substrate  130  by the fluorescent material is emitted with a varied wavelength. 
     Inner Case  170   
       FIG. 16  is a perspective view of the inner case  170 . 
     Referring to  FIGS. 4 and 16 , the inner case  170  includes an insertion unit  174  inserted into the first receiving groove  151  of the heat radiating body  150 , a connection terminal  175  electrically connected to an external power supply, and a second fastening member  172  coupled to the outer case  180 . 
     The inner case  170  is made of a material with excellent insulating properties and endurance, for example, a resin material. 
     The insertion unit  174  is formed in the lower part of the inner case  170 . A side wall of the insertion unit  174  is inserted into the first receiving groove  151  so that an electrical short-circuit between the driving unit  160  and the heat radiating body  150  is prevented. As a result, a withstand voltage of the lighting device  1  can be improved. 
     The connection terminal  175  is, for example, connected to an external power supply in the form of a socket. That is, the connection terminal  175  includes a first electrode  177  at the top thereof, a second electrode  178  on the lateral surface thereof, and an insulating member  179  between the first electrode  177  and the second electrode  178 . The first and second electrodes  177  and  178  are supplied with electric power by an external power supply. Here, since the shape of the terminal  175  is variously changed based on the design of the lighting device  1 , there is no limit to the shape of the terminal  175 . 
     The second fastening member  172  is formed on the lateral surface of the inner case  170  and includes a plurality of holes. The inner case  170  is coupled to the outer case  180  by inserting screws and the like into the plurality of the holes. 
     Moreover, a plurality of second heat radiating holes  176  are formed in the inner case  170 , improving the heat radiation efficiency of the inside of the inner case  170 . 
     Driving Unit  160  and Internal Structure of Inner Case  170   
     Referring to  FIG. 4 , the driving unit  160  is disposed in the first receiving groove  151  of the heat radiating body  150 . 
     The driving unit  160  includes a supporting substrate  161  and a plurality of parts  162  mounted on the supporting substrate  161 . A plurality of the parts  162  include, for example, a converter converting an alternating current supplied from an external power supply into a direct current, a driving chip controlling to drive the light emitting module substrate  130 , an electrostatic discharge (ESD) protective device protecting the light emitting module substrate  130 . The driving unit  160  is not limited to include other components. 
     Here, as shown, the supporting substrate  161  is disposed vertically in order that air flows smoothly in the inner case  170 . Therefore, as compared with a case where the supporting substrate  161  is disposed horizontally, air flows up and down in the inner case  170  due to air convection, thereby improving the heat radiation efficiency of the lighting device  1 . 
     In the meantime, the supporting substrate  161  may be disposed horizontally in the inner case  170 . The supporting substrate  161  can be disposed in various ways without being limited to this. 
     The driving unit  160  is electrically connected to the connection terminal  175  of the inner case  170  by a first wiring  164  and to the light emitting module substrate  130  by a second wiring  165 . 
     Specifically, the first wiring  164  is connected to the first electrode  177  and the second electrode  178  of the connection terminal  175  so that electric power is supplied from an external power supply. 
     The second wiring  165  passes through the through-hole  153  of the heat radiating body  150  and electrically connects the driving unit  160  with the light emitting module substrate  130 . 
     The supporting substrate  161  is disposed vertically in the inner case  170 . Therefore, a long-term use of the lighting device  1  causes the supporting substrate  161  to press and damage the second wiring  165 . 
     Accordingly, in the embodiment, as shown in  FIG. 17 , a projection  159  is formed on the basal surface of the light emitting module substrate  130  in the vicinity of the through-hole  153 , so that it is possible not only to support the supporting substrate  161  but to prevent in advance the second wiring  165  from being damaged. 
     Outer Case  180   
     The outer case  180  is coupled to the inner case  170 , receives the heat radiating body  150 , the light emitting module substrate  130  and the driving unit  160 , etc., and forms an external shape of the lighting device  1 . 
     Since the outer case  180  surrounds the heat radiating body  150 , a burn accident and an electric shock can be prevented and a user can manage the lighting device  1  with ease. Hereinafter, the outer case  180  will be described in detail. 
       FIG. 18  is a perspective view of an outer case  180 . 
     Referring to  FIG. 18 , the outer case  180  includes an opening  181  into which the inner case  170  and the like are inserted, a coupling groove  183  coupled to the second fastening member  172  of the inner case  170 , and a plurality of ventilating holes  182  for allowing air to flow into the lighting device or to flow to the outside of the lighting device. 
     The outer case  180  is made of a material with excellent insulation and endurance, for example, a resin material. 
     The inner case  170  is inserted into the opening  181  of the outer case  180 . The second fastening member  172  of the inner case  170  is coupled to the coupling groove  183  by means of a screw and the like. As a result, the outer case  180  and the inner case  170  are coupled to each other. 
     As described above, the plurality of the ventilating holes  182  as well as the plurality of the first heat radiating holes  102  of the guide member  100  allow air to smoothly flow in the lighting device  1 , thereby improving the heat radiation efficiency of the lighting device  1 . 
     As shown, the plurality of the ventilating holes  182  are formed in the circumference of the top surface of the outer case  180 . The ventilating hole  182  has an arc-shape like a fan. However, there is no limit to the shape of the ventilation hole  182 . Additionally, the coupling groove  183  is formed between the plurality of the ventilating holes  182 . 
     Meanwhile, the lateral surface of the outer case  180  may include at least a marking groove  185  and a plurality of holes  184 . The hole  184  is used to enhance heat radiation efficiency. The marking groove  185  is used to easily managing the lighting device  1 . However, it is not necessary to form the plurality of holes  184  and the marking groove  185 . There is no limit to the formation of the hole  184  and the marking hole  185 . 
     The features, structures and effects and the like described in the embodiments are included in at least one embodiment of the present invention and are not necessarily limited to one embodiment. Furthermore, the features, structures, effects and the like provided in each embodiment can be combined or modified in other embodiments by those skilled in the art to which the embodiments belong. Therefore, contents related to the combination and modification should be construed to be included in the scope of the present invention. 
     The features, structures and effects and the like described in the embodiments are included in at least one embodiment of the present invention and are not necessarily limited to one embodiment. Furthermore, the features, structures, effects and the like provided in each embodiment can be combined or modified in other embodiments by those skilled in the art to which the embodiments belong. Therefore, contents related to the combination and modification should be construed to be included in the scope of the present invention.