Wavelength converting member

1. A wavelength converting member comprising a plate-like sintered body having one principal surface as a light entrance surface and the other principal surface opposite to the entrance surface as a light exit surface, wherein

the plate-like sintered body has a porosity of 1.0% or less which includes fluorescent material grains containing an activator and light-transmitting material grains,

the fluorescent material containing the activator is a material represented by the general formula A 3 B 5 O 12 :Ce, in the formula, A being at least one selected from the group consisting of Y and Gd, and B being Al,

the light-transmitting material is Al 2 O 3 or a material in which at least Sc 2 O 3 or Ga 2 O 3 is contained in Al 2 O 3 ,

at least the entrance surface and the exit surface are a non-processed sintered surface on which the fluorescent material grains and the light-transmitting material grains are exposed, and the non-processed sintered surface has a calculated average roughness Ra, as an average of 10 points measured with a measurement length of 4 mm, of 0.1 μm to 0.5 μm,

and the fluorescent material grains exposed on the non-processed sintered surface have a calculated average roughness Ra 1 , as an average of 20 points measured with a measurement length of 1 μm, of 0.2 nm to 0.5 nm, and the light-transmitting material grains exposed on the non-processed sintered surface have a calculated average roughness Ra 2 , as an average of 20 points measured with a measurement length of 1 μm, of 0.3 nm to 0.7 nm.

2. The wavelength converting member according to claim 1 , wherein an average diameter d 1 of the 20 fluorescent material grains is 0.5 μm to 5 μm, an average diameter d 2 of the 20 light-transmitting material grains is 1 μm to 10 μm, an occupying ratio of the fluorescent material grains is 22 volume % to 35 volume %, and an occupying ratio of the light-transmitting material grains is 65 volume % to 78 volume %.

3. The wavelength converting member according to claim 2 , wherein the average diameter d 1 of the 20 fluorescent material grains is 0.1 times to 0.78 times smaller than the average diameter d 2 of the 20 light-transmitting material grains.

4. The wavelength converting member according to claim 1 , wherein the calculated average roughness Ra 2 of the light-transmitting material grains exposed on the non-processed sintered surface, which is obtained as an average of 20 points measured with a measurement length of 1 μm, is 1.2 times to 2.0 times larger than the calculated average roughness Ra 1 of the fluorescent material grains exposed on the non-processed sintered surface, which is obtained as an average of 20 points measured with a measurement length of 1 μm.

5. The wavelength converting member according to claim 3 , wherein the calculated average roughness Ra 2 of the light-transmitting material grains exposed on the non-processed sintered surface, which is obtained as an average of 20 points measured with a measurement length of 1 μm, is 1.2 times to 2.0 times larger than the calculated average roughness Ra 1 of the fluorescent material grains exposed on the non-processed sintered surface, which is obtained as an average of 20 points measured with a measurement length of 1 μm.

6. A wavelength converting member comprising:

a first layer which contains a YAG-based fluorescent material containing an activator and Al 2 O 3 ;

an intermediate layer which is laminated on the first layer and includes Al 2 O 3 in which grains with a diameter of 20 μm to 300 μm include no less than 90% of total grain number; and

a second layer which is laminated on the intermediate layer and includes a YAG-based material containing an activator in an amount of no more than 10% of an activator content in the first layer and Al 2 O 3 , wherein

a connected structure is provided in which Al 2 O 3 grains are connected to each other in each layer and Al 2 O 3 grains are also connected to each other at each layer interface,

all of the first layer, the intermediate layer, and the second layer include a sintered body having a porosity of 1.0% or less, surfaces of the first layer and the second layer being a non-processed sintered surface, the non-processed sintered surface has a calculated average roughness Ra, as an average of 10 points measured with a measurement length of 4 mm, of 0.1 μm to 0.5 μm, and

a calculated average roughness Ra 1 of the YAG-based fluorescent material grains exposed on the non-processed sintered surface, which is obtained as an average of 20 points measured with a measurement length of 1 μm, is 0.2 nm to 0.5 nm and a calculated average roughness Ra 2 of Al 2 O 3 grains exposed on the non-processed sintered surface, which is obtained as an average of 20 points measured with a measurement length of 1 μm, is 0.3 nm to 0.7 nm.

7. The wavelength converting member according to claim 6 , wherein

an average diameter d 1 of 20 of the YAG-based fluorescent material grains containing an activator in the first layer and the YAG-based material grains in the second layer is 0.5 μm to 5 μm and an average diameter d 2 of the 20 Al 2 O 3 grains in each of the first layer and the second layer is 1 μm to 10 μm, and

an occupying ratio of the YAG-based fluorescent material grains containing an activator in the first layer and the YAG-based material grains in the second layer is 22 volume % to 35 volume % in each of the first layer and the second layer, respectively, and an occupying ratio of the Al 2 O 3 grains in each of the first layer and the second layer is 65 volume % to 78 volume %, respectively.

8. The wavelength converting member according to claim 7 , wherein

the YAG-based fluorescent material containing an activator that is contained in the first layer is (Y 1-s Gd s ) 3 (Al 1-t Ga t ) 5 O 12 :Ce (0≦s≦0.33, 0≦t≦0.2).

9. The wavelength converting member according to claim 7 , wherein

the YAG-based fluorescent material containing an activator that is contained in the first layer is (Y 1-x Gd s ) 3 (Al 1-t Ga t ) 5 O 12 :Ce (0≦s≦0.33, 0≦t≦0.2).