Light emitting device, lighting system, backlight unit for display device and display device

Abstract

To enhance emission efficiency and color rendering, a light emitting device 1 comprises: at least one light source 3 ; at least one first emitting section 4 having at least one sort of luminescent material that can emit light including a wavelength component that is longer than the light emitted from light source 3 when excited by the light emitted from light source 3 ; at least one second emitting section 5 having at least one sort of luminescent material that can emit light including a wavelength component that is longer than the light emitted from first emitting section 4 when excited by the light emitted from light source 3 and first emitting section 4 ; wherein light emitting device 1 comprises at least one light shielding unit 6 that protects at least a part of the light emitted from first emitting section 4 from entering second emitting section 5.

1 . A method for adjusting the color of white light and emitting the white light, the method comprising:
 preparing a first blue light source, a first luminescent material that is excited by a first blue light emitted by the first blue light source and thereby emits green light, a second blue light source, and a second luminescent material that is excited by a second blue light emitted by the second blue light source and thereby emits red light;   generating the white light through mixing the first blue light emitted by the first blue light source, the green light emitted by the first luminescent material, the second blue light emitted by the second blue light source, and the red light emitted by the second luminescent material; and   adjusting a balance in intensity of the first and second blue lights, green light, and red light contained in the white light by adjusting a ratio of electric power supplied to the first blue light source and electric power supplied to the second blue light source.   
     
     
         2 . The method according to  claim 1 , wherein the adjusting of the ratio of electric power comprises adjusting a ratio of a value of an electric current supplied to the first blue light source and a value of an electric current supplied to the second blue light source. 
     
     
         3 . The method according to  claim 1 , wherein:
 the first blue light source and the second blue light source are driven by electric pulses; and   the adjusting of the ratio of electric power comprises adjusting a ratio of a pulse lighting period of the first blue light source and a pulse lighting period of the second blue light source.   
     
     
         4 . The method according to  claim 1 , wherein:
 the first blue light source is a light emitting diode, laser diode, or an electroluminescence element; and   the second blue light source is a light emitting diode, a laser diode, or an electroluminescence element.   
     
     
         5 . The method according to  claim 1 , wherein the second luminescent material is a phosphor represented by following Formula (3),
   M a A b D C E d X e   (3)
   
       where
 M represents one or more elements containing at least Eu and selected from the group consisting of Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm and Yb, 
 A represents one or more elements selected from bivalent metal elements other than M, 
 D represents one or more elements selected from tetravalent metal elements, 
 E represents one or more elements selected from trivalent metal elements, 
 X represents one or more elements selected from a group consisting of O, N, and F, and 
 a value of a, b, c, d, e is selected from the value satisfying all of the following conditions:
     a  is a number of 0.00001<a<0.1 
     a  and  b  establish a relationship of  a+b= 1 
     c  is a number of 0.5 ≦c≦ 4 
     d  is a number of 0.5 ≦d≦ 8 
     c, d , and  e  establish a relationship of 0.8×(2/3+4/3 ×c+d )≦ e,  
 
   and 
     c, d , and  e  establish a relationship of  e≦ 1.2×(2/3+4/3 ×c+d )
 
 
 
     
     
         6 . A method for producing an intended colored white light, the method comprising:
 a step for producing a first mixed light containing a first blue light and green light, by using a first blue light source which emits the first blue light and a first luminescent material which is exited by the first blue light emitted by the first blue light source and thereby emits the green light;   a step for producing a second mixed light containing a second blue light and red light and being different in chromaticity from the first mixed light, by using a second blue light source which emits the second blue light and a second luminescent material which is exited by the second blue light emitted by the second blue light source and thereby emits the red light;   a step for mixing the first mixed light and the second mixed light to produce a white light containing the first and second blue lights, green light and red light; and   a step for adjusting a balance in intensity of the first and second blue lights, green light and red light contained in the white light.   
     
     
         7 . The method according to  claim 6 ,
 wherein the first light source is a light emitting diode, a laser diode, or an electroluminescence element; and   the second light source is a light emitting diode, a laser diode, or an electroluminescence element.   
     
     
         8 . The method according to  claim 7 ,
 wherein the adjusting step comprises adjusting a ratio of electric power supplied to the first blue light source and electric power supplied to the second blue light source.