a thickness or a size of each layer may be magnified , omitted or schematically shown for the purpose of convenience and clearness of description . the size of each component may not necessarily mean its actual size . it should be understood that when an element is referred to as being ‘ on ’ or “ under ” another element , it may be directly on / under the element , and / or one or more intervening elements may also be present . when an element is referred to as being ‘ on ’ or ‘ under ’, ‘ under the element ’ as well as ‘ on the element ’ may be included based on the element . hereafter , detailed technical characteristics to be embodied will be described in detail with reference to the accompanying drawings . fig1 is a perspective view of an led lighting device according to an embodiment . fig2 is an exploded perspective view of the led lighting device . fig3 is a side exploded view of the led lighting device . fig4 is a side view of the led lighting device . referring to fig1 to 4 , the led lighting device basically includes an upper case 200 , a lower case 300 , a light guide plate 500 and a light source unit 700 . further , in the embodiment , light can be prevented from being emitted through the light guide plate 500 by providing a cap 100 on the side of the lower case 300 . also , a reflective sheet 400 may be disposed between the upper case 200 and the light guide plate 500 . the upper case 200 and the lower case 300 function as a case of the led lighting device and are disposed in an attachable and removable manner . the upper case 200 includes , as shown in fig2 to 4 , a plate - shaped base 210 and a right - left edge 230 which is stepped with respect to the base 210 and extends from the base 210 . here , the base 210 is formed thicker than the edge 230 . when the upper case 200 is coupled to the lower case 300 , the base 210 hereby presses the top of the reflective sheet 400 , so that the reflective sheet 400 and the light guide plate 500 become closer to each other . therefore , the reflective sheet 400 and the light guide plate 500 can be prevented from moving . the edge 230 has a rectangular shape as a whole . an open recess ( see reference numeral 230 a of fig2 ) in which a driver is disposed is formed in the right and / or left side of the edge 230 . as shown in fig3 , a position of the edge 230 , which is connected to the base 210 , includes a locking recess 230 b formed in the longitudinal direction of the edge 230 . a substrate 710 of the light source unit 700 is inserted into the locking recess 230 b . consequently , the locking recess 230 b functions to stably fix the light source unit 700 . the lower case 300 includes , as shown in fig2 to 4 , a body 310 including two vertical planes 301 and 303 , a bezel 330 extending perpendicular to the one vertical plane 301 of the body 310 , and a guide 350 projecting perpendicular to the other vertical plane 303 of the body 310 . here , the body 310 includes one side 301 on which the light source unit 700 is disposed and the other side 303 on which the edge 230 of the upper case 200 is disposed . the two planes 301 and 303 are perpendicular to each other . an insertion groove ( see reference numeral 300 a of fig2 ) and an opening ( see reference numeral 300 b of fig2 ) are formed in the side of the body 310 . here , the driver ( see reference numeral 900 of fig2 ) driving the light source unit 700 is disposed in the insertion groove 300 a . the opening 300 b is formed in such a manner that the insertion groove 300 a is connected to the one plane 301 of the body 310 , on which the light source unit 700 is disposed . meanwhile , the corner of the body 310 is rounded and relives external impact . subsequently , the body 310 includes a guide recess 310 a formed inside the body 310 under the guide 350 in the longitudinal direction of the body 310 . a plurality of the guide recesses 310 a may be provided and disposed in parallel with the longitudinal direction of the body 310 . the guide recess 310 a of the body 310 increases the surface area for heat radiation . therefore , the guide recess 310 a functions to effectively radiate heat generated from the light source unit 700 . a louver ( see reference numeral 50 of fig8 to 10 ) which adjusts the light direction may be inserted and set in the guide recess 310 a of lower case 300 . the louver 50 functions to adjust the light direction when the light of the light source unit 700 is outwardly emitted through the light guide plate 500 . subsequently , the bezel 330 of the lower case 300 , as shown in fig3 and 4 , supports both sides of the bottom surface of the light guide plate 500 . when the light emitted from the light source unit 700 is outwardly emitted , the bezel 330 functions to prevent light spot generated due to a short optical path . the bezel 330 determines an effective area , i . e ., a light emitting area , depending on the width or size thereof . therefore , in terms of optical efficiency , it is recommended that the bezel 330 should be reduced as much as possible in such a manner that the effective area is not reduced within a range in which no light spot is generated . as shown in fig2 to 4 , the guide 350 of the lower case 300 is molded in a projection shape , perpendicular to the other vertical plane 303 of the body 310 . when the upper case 200 is coupled to the lower case 300 , the guide 350 prevents the upper case 200 from moving right and left . here , the height of the projecting guide 350 may be the same as the thickness of the edge 230 of the upper case 200 . after the upper case 200 is coupled to the lower case 300 , the edge 230 of the upper case 200 is , as shown in fig4 , seated on the vertical plane 303 of the body 310 of the lower case 300 . the upper case 200 is coupled to the lower case 300 by a screw 10 . the upper case 200 and the lower case 300 have a quadrangular cross section having an open lower portion . in the led lighting device , when the structures disposed inside the case , such as the light source unit 700 , the light guide plate 500 and the reflective sheet 400 need repairing , the upper case 200 can be separated from the lower case 300 . with regard to the led lighting device , heat transfer characteristics of the upper and lower cases 200 and 300 are improved by disposing a heat radiation sheet ( not shown ). therefore , a heat radiating characteristic can be enhanced . the upper and lower cases 200 and 300 may be formed of a pc material which reduces the weights thereof and may be also formed of a material having a high thermal conductivity in order to excellently radiate heat generated from the light source unit 700 to the outside of the case . for example , the upper and lower cases 200 and 300 may be formed of at least one metallic material selected from the group consisting of cu , ag , au , ni , al , cr , ru , re , pb , cr , sn , in , zn , pt , mo , ti , ta and w , or may be formed of an alloy including the metallic materials . further , to add elasticity to the upper and lower cases 200 and 300 , the upper and lower cases 200 and 300 may be formed of an elastic material . subsequently , the reflective sheet 400 has a plate shape corresponding to one side of the light guide plate 500 and is disposed between the upper case 200 and the light guide plate 500 . unlike the case , the reflective sheet 400 is made of a ductile material or a plastic material . if the base 210 of the upper case 200 is coated with a reflective material , the reflective sheet 400 may be removed . when the light emitted from the light source unit 700 is emitted to the outside through the light guide plate 500 , the reflective sheet 400 reflects the light emitted to the rear of the light guide plate 500 , and then the light is emitted to the outside . the light guide plate 500 is optically coupled to the light source unit 700 . that is , the light guide plate 500 is disposed in parallel with the light source unit 700 and guides the path of the light emitted from the light source unit 700 . as shown in fig2 to 4 , the light guide plate 500 has a rectangular plate shape and a level difference surface in the lower portion thereof . here , the bezel 330 of the lower case 300 is disposed on the level difference surface and supports the light guide plate 500 . the light guide plate 500 functions to convert a point light source generated by the light source unit 700 into a surface light source . here , one side of the light guide plate 500 may include a particular pattern formed thereon or a coating film ( see reference numeral 510 of fig5 ) having a roughness . the coating film 510 having the particular pattern or a roughness functions to diffuse or scatter the light , and then emits the light to the outside . the light guide plate 500 may be made of a transparent resin and may be printed by a silk - screen printing method . as shown in fig5 , the embodiment includes a reflective sheet 30 disposed in a contact area of the bezel 330 of the lower case 300 and the lower portion of the light guide plate 500 . the reflective sheet 30 may be formed on the bezel 330 of the lower case 300 or may be disposed between the lower case 300 and the light guide plate 500 . when the light emitted from the light source unit 700 is irradiated to the bezel 330 of the lower case 300 , the reflective sheet 30 enhances the back reflectance of the light , thereby substantially improving the optical efficiency of the light which is outwardly emitted . the light source unit 700 includes , as shown in fig2 to 4 , a substrate 710 , a light emitting device 730 and a driving driver 750 . here , the substrate 710 is a rectangular printed circuit board . the light emitting device 730 includes a plurality of leds and is disposed on one side of the substrate 710 in the longitudinal direction of the substrate 710 . the light emitting device 730 includes the leds emitting the same colored light or includes the leds emitting differently colored lights . therefore , light having various colors can be emitted by a combination of the two different colors , so that an emotional lighting device can be implemented . the led includes a light emitting diode emitting at least one of blue , red and green colors . though not shown in the drawings , the led is able to emit light having its own color due to a sealed transparent resin in the upper portion thereof . here , the led emitting blue light is also able to emit white light as well by using a resin including a yellow fluorescent material . while the led is taken as an example of a light source in the embodiment , any device capable of emitting light can be included in the light source , without being limited to this . the driving driver 750 may be provided on the other side or end of the substrate 710 , on which the light emitting device 730 is not disposed . a plurality of the light source units 700 are provided and disposed on the body 310 of the lower case in such a manner that the light emitting devices 730 disposed on the substrate 710 face each other . here , the substrates 710 of the light source unit 700 are , as shown in fig3 and 4 , inserted into the locking recesses 230 b of the upper case 200 respectively . though not shown in the drawings , a heat radiation sheet may be disposed on a contact area of the light sources unit 700 and the body 310 of the lower case 300 . the heat radiation sheet can improve a heat radiating characteristic by transferring the heat generated from the light source unit 700 to the lower case 300 and radiating the heat to the outside . in the led lighting device of the embodiment , a photo luminescent film ( not shown ) including a fluorescent material may be disposed between the light source unit 700 and the light guide plate 500 . the photo luminescent film functions to change the color of the light by converting a portion of the wavelength of the light emitted from the light source unit 700 . here , the photo luminescent film may include a transparent resin and a fluorescent material contained in the transparent resin . here , a curing agent or an additive may be included in the transparent resin . the curing agent functions to cure the transparent resin . the additive functions to disperse uniformly the fluorescent material within the transparent resin . also , a diffusing agent may be included in the transparent resin . here , the diffusing agent functions to increasing the excitation ratio of the fluorescent material by improving the refractive index of the light source . subsequently , the driver 900 is , as shown in fig1 and 2 , disposed to be inserted into the open recess 230 a of the edge 230 of the upper case 200 and insertion groove 300 a of the body 310 of the lower case 300 . then , the driver 900 is electrically connected to the driving driver ( see reference numeral 750 of fig2 ) of the light source unit 700 disposed on one side of the lower case 300 . next , the cap 100 is disposed on the front and rear sides of the light guide plate 500 disposed within the case and prevents the light generated from the light source unit 700 from being emitted to the front and rear sides of the light guide plate 500 . the cap 100 includes a coupling hole 100 a which is coupled to a side of the guide recess 310 a of the lower case 300 by means of a screw ( see reference numeral 20 of fig2 ). the cap 100 may be made of a metallic material or a lightweight plastic material . fig5 is a cross sectional view showing a first structure of a coating film disposed on a light guide plate . referring to fig5 , when the light emitted from the light source unit 700 is emitted to the outside through the light guide plate 500 , a light emitting effective area “ ad ” is determined by an opening formed through the coupling of the upper case 200 and the lower case 300 . here , the light emitting effective area “ ad ” corresponds to an area through which the light emitted from the light source unit 700 is emitted to the outside the light guide plate 500 . a light emitting ineffective area “ nad ” corresponds to an area where the light which is emitted from the light source unit and passes through the light guide plate is not emitted by being blocked by the bezel 330 of the lower case 300 . the coating film 510 is formed on the light guide plate 500 . the roughness may be formed on a portion of the surface of the coating film 510 or may be formed on the entire surface of the coating film 510 in order to improve the light uniformity . as a result , the light guide plate 500 causes the light emitted through the top surface of the light guide plate 500 to be diffused or scattered in direction of the bottom surface of the light guide plate 500 , thereby improving not only the optical efficiency but the uniformity of the light which is emitted to the outside . though the roughness of the coating film 510 may be uniform on the entire surface thereof , the roughness may be different depending on the position of the surface of the coating film 510 . in other words , the roughness of the coating film 510 formed in the central portion of the light guide plate 500 , which corresponds to the light emitting effective area “ ad ” is larger than the roughness of the coating film 510 formed in the peripheral portion of the light guide plate 500 , which corresponds to the light emitting ineffective area “ nad ”. this intends to substantially improve the light diffusivity effect and the light scattering effect by increasing the roughness of the portion of the coating film 510 , which corresponds to the light emitting effective area “ ad ”. though not shown in the drawings , the coating film 510 may be formed on the top and the bottom surfaces of the light guide plate 500 . here , the surface roughness of the coating film 510 of the bottom surface may be the same as or different from that of the top surface of the coating film 510 . as a result , it is possible to improve the light uniformity and the optical efficiency . another embodiment will be provided . the same effect as the effect mentioned above can be obtained by forming the roughness on the bottom surface itself of the light guide plate 500 in place of the coating film 510 formed on the bottom surface of the light guide plate 500 . fig6 is a cross sectional view showing a second structure of a coating film disposed on a light guide plate . referring to fig6 , as in fig5 , the light guide plate 500 corresponds to the light emitting effective area “ ad ” and the light emitting ineffective area “ nad ”. the roughness is locally or entirely formed on one side of the light guide plate 500 . though the roughness may be uniformly formed on the entire surface of the light guide plate 500 , the roughness may be different depending on the position of the surface of the light guide plate 500 . in other words , the roughness formed in the central portion of the light guide plate 500 , which corresponds to the light emitting effective area “ ad ” is larger than the roughness formed in the peripheral portion of the light guide plate 500 , which corresponds to the light emitting ineffective area “ nad ”. this intends to substantially improve the light diffusivity effect and the light scattering effect by increasing the roughness of the surface of the light guide plate 500 , which corresponds to the light emitting effective area “ ad ”. though not shown in the drawings , the coating film 510 may be formed on the top and the bottom surfaces of the light guide plate 500 . here , the surface roughness of the coating film 510 of the bottom surface may be the same as or different from that of the top surface of the coating film 510 . as a result , it is possible to improve the light uniformity and the optical efficiency . another embodiment will be provided . the same effect as the effect mentioned above can be obtained by forming the roughness on the bottom surface itself of the light guide plate 500 in place of the coating film 510 formed on the bottom surface of the light guide plate 500 . fig7 is a cross sectional view showing a third structure of a coating film disposed on a light guide plate . referring to fig7 , as in fig5 , the light guide plate 500 corresponds to the light emitting effective area “ ad ” and the light emitting ineffective area “ nad ”, and has a shape of a plurality of lenses . here , the lens has a size of a micro unit . the shape of the lens may be locally or entirely formed on the top surface of the light guide plate 500 . since a subsequent effect to this has been described above , a description of the effect will be omitted . distances between the lenses of the light guide plate 500 may be the same as each other on the entire surface of the light guide plate 500 , or may be different from each other depending on a position of the light guide plate 500 . that is to say , a distance “ d 1 ” between the lenses formed in the central portion of the light guide plate 500 , which corresponds to the light emitting effective area “ ad ” is less than a distance “ d 2 ” between the lenses formed in the peripheral portion of the light guide plate 500 , which corresponds to the light emitting ineffective area “ nad ”. though not shown in the drawings , the bottom surface itself of the light guide plate 500 may include a plurality of the lenses and a predetermined pattern formed therein . fig8 to 10 are cross sectional views showing a first to a third structures a lourver 50 coupled to the led lighting device . referring to fig8 to 10 , the louver 50 is coupled in a sliding way to the both guide recesses 310 a formed in the longitudinal direction of the body 310 of the lower case 300 . the louver 50 may be made of a plastic material or a metallic material . the inner surface of the louver 50 may be coated with a reflective material . the shape of the louver 50 may be , as shown in fig8 and 9 , symmetrical with respect to the opening of the case in accordance with the orientation angle of the light emitted from the light guide plate 500 , or may be , as shown in fig1 , asymmetrical with respect to the opening of the case . depending on the size of a light irradiation area , fig8 shows that some of the light irradiation direction of the louver 50 may be formed in the form of a symmetrical curve . fig9 shows that some of the light irradiation direction of the louver 50 may be formed in the form of a symmetrical flat plane . fig1 shows that some of the light irradiation direction of the louver 50 may be formed in the form of an asymmetric structure including the curve and the flat plane . although embodiments of the present invention were described above , these are just examples and do not limit the present invention . further , the present invention may be changed and modified in various ways , without departing from the essential features of the present invention , by those skilled in the art . for example , the components described in detail in the embodiments of the present invention may be modified . further , differences due to the modification and application should be construed as being included in the scope and spirit of the present invention , which is described in the accompanying claims .