Phosphor layer, image display device employing the same and method for making the phosphor layer

Abstract

A phosphor layer having improved contrast and brightness characteristics and a display device including the same are provided. The phosphor layer is made out of an ultra-fine pigment, a dispersant, a phosphor, a photosensitizer and a binder. The phosphor has a uniform distribution along the thickness of the phosphor layer, and the pigment varies in content over the thickness of the phosphor layer. A method of forming the phosphor layer is based on existing phosphor layer processes and includes a reduced number of processing steps than a filter screen method, thereby markedly lowering the manufacturing costs. The phosphor layer can be used in a cathode ray tube, a plasma display panel, a field emission display, and an organic electroluminescent device.

1 - 4 . (canceled) 
     
     
         5 . A method of forming a phosphor layer, the method comprising:
 preparing a pigment dispersion by mixing together an ultra-fine pigment, a dispersant, and a solvent;   preparing a composition for forming a phosphor layer by mixing together the pigment dispersion with a phosphor, a photosensitizer, and a binder;   coating the composition for forming the phosphor layer on an upper surface of a substrate; and   exposing and developing the phosphor layer on the substrate so that the phosphor layer is patterned.   
     
     
         6 . The method of  claim 5 , the amount of the ultra-fine pigment is in the range of 0.05-30 parts by weight with respect to 100 parts by weight of the phosphor. 
     
     
         7 . The method of  claim 5 , the ultra-fine pigment has an average particle diameter ranging from 10 nm to 300 nm. 
     
     
         8 . The method of  claim 5 , the ultra-fine pigment is made out of a material selected from the group consisting of TiO 2 —CoO—NiO—ZrO 2 , Fe 2 O 3 , and CoO—Al 2 O 3 . 
     
     
         9 . A method of forming a phosphor layer, the method comprising:
 preparing a pigment dispersion by mixing together an ultra-fine pigment, a dispersant, and a solvent;   preparing a composition for forming a phosphor layer by mixing together the pigment dispersion with a phosphor, a photosensitizer, and a binder; and   printing the composition for forming the phosphor layer on an upper surface of a substrate.   
     
     
         10 . The method of  claim 9 , the amount of the ultra-fine pigment is in the range of 0.05-30 parts by weight with respect to 100 parts by weight of the phosphor. 
     
     
         11 . The method of  claim 9 , the ultra-fine pigment has an average particle diameter ranging from 10 nm to 300 nm. 
     
     
         12 . The method of  claim 9 , wherein the ultra-fine pigment is made out of a material selected from the group consisting of TiO 2 —CoO—NiO—ZrO 2 , Fe 2 O 3 , and CoO—Al 2 O 3 . 
     
     
         13 - 16 . (canceled) 
     
     
         17 . A display, comprising:
 a faceplate; and   a first phosphor layer of a first primary color formed on the faceplate, first phosphor layer comprising a plurality of sublayers, each sublayer comprising pigment of the same primary color, each sublayer having a different pigment concentration from other sublayers within the first phosphor layer.   
     
     
         18 . The display of  claim 17 , each sublayer in said first phosphor layer forming a stepwise pigment concentration gradient that varies with distance from the faceplate. 
     
     
         19 . The display of  claim 18 , a sublayer furthest from the faceplate within said first phosphor layer having a lowest pigment concentration and a sublayer closest to the faceplate within said first phosphor layer having a highest pigment concentration. 
     
     
         20 . The display of  claim 18 , said first phosphor layer being patterned. 
     
     
         21 . The display of  claim 17 , further comprising a second and different phosphor layer of a second and different primary color formed on the faceplate. 
     
     
         22 . The display of  claim 21 , the second phosphor layer comprising a plurality of sublayers, each sublayer in the second phosphor layer comprising pigment of the same second primary color, each sublayer having a different pigment concentration from other sublayers within the second phosphor layer. 
     
     
         23 . The display of  claim 22 , the sublayers within each of said first and said second phosphor layers being arranged to have a decreasing pigment content in a direction going away from the faceplate. 
     
     
         24 . A method of forming phosphor layers on a faceplate, comprising:
 preparing a first phosphor composition of a first color and having a first pigment concentration;   forming a first sublayer on the faceplate using said first phosphor composition of said first color;   preparing a second phosphor composition of said first color and having a second and different pigment concentration;   forming a second sublayer on first sublayer on the faceplate using said second phosphor composition;   preparing a third phosphor composition of said first color and having a third and different pigment concentration; and   forming a third sublayer over the second sublayer on the faceplate using said third phosphor composition.   
     
     
         25 . The method of  claim 24 , further comprising patterning said first, second and third sublayers simultaneously after forming the first, second and third sublayers when not already patterned. 
     
     
         26 . The method of  claim 24 , said first, second and third sublayers being applied to the faceplate by printing so that the first, second and third sublayers are patterned on the faceplate. 
     
     
         27 . The method of  claim 25 , repeating the above method for a second and different primary color and a third and different primary color. 
     
     
         28 . The method of  claim 24 , said third pigment concentration being less than said second pigment concentration, said second pigment concentration being less than said first pigment concentration. 
     
     
         29 . The method of  claim 27 , said third pigment concentration being less than said second pigment concentration, said second pigment concentration being less than said first pigment concentration for all three colors.