Phosphor and image displaying device employing the same
The present invention provides a red-emitting phosphor emitting luminescence of excellent color purity with high efficiency under the excitation with near UV light, and it also provides a color image displaying device employing that phosphor. This phosphor comprises an ARS 2 matrix (A is at least one of Na, K and Rb, and R is at least one of Y, Gd and Lu) doped with 0.003 to 0.3 mol % of Bi and 0.1 to 3 mol % of Mn, and is suitable as a red-emitting phosphor used in a color image displaying device without a color filter.
1. A red-emitting phosphor, comprising:
a matrix represented by the following formula (1):
ARS 2 (1)
in which A is at least one element selected from the group consisting of Na, K and Rb; and R is at least one element selected from the group consisting of Y, Gd and Lu; and
small amounts of Bi and Mn,
wherein the content of Bi is 0.003 to 0.3 mol %, the content of Mn is 0.1 to 3 mol %, and the molar ratio of Bi/Mn is less than ⅓, and
wherein the red-emitting phosphor emits red luminescence when exposed to light in the wavelength range of 380 to 430 nm.
2. The phosphor according to claim 1 , having a crystal structure of hexagonal system.
3. The phosphor according to claim 2 , whose crystal structure is an α-NaFeO 2 type hexagonal system in which the sulfur atoms are partly replaced with oxygen atoms.
4. An image displaying device comprising:
an excitation light source giving off near UV light having a peak in the wavelength range of 380 to 430 nm,
a phosphor layer comprising a phosphor emitting blue luminescence under the excitation with said near UV light,
a phosphor layer comprising a phosphor emitting green luminescence under the excitation with said near UV light, and
a phosphor layer comprising a phosphor emitting red luminescence under the excitation with said near UV light, and comprising:
a matrix represented by the following formula (1):
ARS 2 (1)
in which A is at least one element selected from the group consisting of Na, K and Rb; and R is at least one element selected from the group consisting of Y, Gd and Lu;
and
small amounts of Bi and Mn,
wherein the content of Bi is 0.003 to 0.3 mol %, the content of Mn is 0.1 to 3 mol %, and the molar ratio of Bi/Mn is less than ⅓;
wherein
said phosphor layers are arranged in planar positions, according to each of which a liquid crystal element is provided so as to control transmittance of the excitation light or of the luminescence emitted from each corresponding phosphor.
5. The device according to claim 4 , wherein said blue-emitting phosphor comprises:
a matrix represented by the following formula (2):
NaRS 2 (2)
in which R is at least one element selected from the group consisting of Y, Gd and Lu, and
0.01 to 1 mol % of Bi,
wherein blue-emitting phosphor emits blue luminescence when exposed to light in the wavelength range of 380 to 430 nm.
6. The device according to claim 4 , wherein said excitation light source is a near UV light-emitting diode.
7. The phosphor according to claim 1 , wherein A is Na.