Patent Application
20080265747
1. Field of the Invention
The present invention relates to a phosphor, and a light-emitting member and an image display apparatus using the same.
2. Description of the Related Art
Various phosphor materials have been recently researched to improve luminance, color purity, and the like for a display phosphor. An electron beam excited phosphor conventionally represented by CRT includes ZnS:Cu, Al; ZnS:Ag, Al; Y2O2S:Eu, and the like. Phosphor materials such as SrGa2S4:Eu and the like have been also recently researched as multicomponent sulfide phosphor material in a flat panel display application.
However, in a P22 type CRT phosphor of the prior art, sufficient performance cannot be obtained in both color reproducing range and luminance. The green phosphor SrGa2S4:Eu described in Japanese examined patent publication No. 60-38431 has wider color reproducing range compared to the conventional ZnS:Cu, Al, but further enlargement of color reproducing range and enhancement in luminance have been desired. U.S. Pat. No. 3,639,254 discloses phosphor R1-xGa2S4:Eux (R is alkaline earth metal selected from Ca, Sr, Ba). Japanese Patent Application Laid-Open No. 2007-36041 discloses phosphor Sr1-x-yCaxBayGa2S4:Eu. Japanese Patent Application Laid-Open No. 2007-112950 (correspond to US Publication US-2007-0090748) discloses phosphor SrxBa1-xGa2S4:Eu (0<X<1).
The present invention provides a high luminance phosphor, a light-emitting member capable of displaying a high color reproducing range, and an image display apparatus using the same.
A first aspect of the present invention relates to a phosphor including BaxSr1-xGa2S4:Eu, where 0<X<0.5.
A second aspect of the present invention relates to a phosphor including BaxSr1-xGa2S4:Eu, where 0.03≦X≦0.4.
A third aspect of the present invention relates to a light-emitting member including a base member; and a phosphor arranged on the base member; wherein the phosphor includes the phosphor of the first or the second aspect.
A fourth aspect of the present invention relates to a light-emitting member including a base member; and at least three types of phosphors having different light emission peak wavelength from each other; wherein one type of the phosphor includes the phosphor of the first or the second aspect.
A fifth aspect of the present invention relates to an image display apparatus including the light-emitting member according to the third aspect or the fourth aspect; and an excitation source for light emitting the light-emitting member.
According to the phosphor of the present invention, the color reproducing range can be enlarged and the luminance can be enhanced. Therefore, a brighter image display apparatus of satisfactory color reproducibility can be obtained.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
The embodiments of the present invention will now be described in detail.
The phosphor material of the present invention has a host material represented by a composition formula (general formula) of BaxSr1-xGa2S4 and europium which acts as a luminescent center (activator). Where, X representing the composition ratio of the host material takes a value in a range of 0<X<0.5, and the composition will not become SrGa2S4 or Ba0.5Sr0.5Ga2S4.
The concentration of the europium acting as the luminescent center is preferably adjusted to 0.01 to 10 atomic percent with respect to the sum of the elements Sr and Ba of the elements composing the host material. The Eu compound includes europium metal, europium chloride, europium fluoride, europium oxide, or the like.
Regarding the phosphor material of the present invention, changing the composition ratio X of the host material allows changing emission color from 532 nm being a light emission peak wavelength of SrGa2S4:Eu to 522 nm being a light emission peak wavelength of Ba0.5Sr0.5Ga2S4:Eu, whereby an optimum green light emission color can be set. The change in emission color at this moment is shown in
The luminance of the phosphor material of the present invention changes by changing the Ba composition ratio. For the image display apparatus, the X value of the composition ratio of the host material is preferably selected from a range of 0<X<0.5 in view of higher luminance. If X=0.5, the light emission efficiency lowers by about 5% compared to SrGa2S4:Eu (X=0) which is not added with Ba. The X value of the composition ratio of the host material is preferably selected from a range of 0.03≦X≦0.4 in view of widening the color gamut. If the X value is in such range, the light emission efficiency can be increased and the color gamut can be further widened. The X value is more preferably selected from a range of 0.1≦X≦0.4.
The composition ratio of the host material can be checked with X-ray photoelectron spectroscopy (XPS), Energy Dispersive X-ray Spectroscopy (EDS), X-ray fluorescence spectroscopy, or the like.
Processes of producing the phosphor material of the present invention include solid phase crystallization method which mixes and crystallizes the material powder. One example thereof will be described.
First, strontium sulfide powder (SrS), barium sulfide powder (BaS), gallium sulfide powder (Ga2S3), and europium chloride powder (EuCl3) are mixed. Here, the materials are mixed to meet the weight ratio of SrS:BaS:Ga2S3:EuCl3≅0.39:0.14:1.0:0.03 in order to obtain the composition ratio represented by Ba0.2Sr0.8Ga2S4:Eu. The composition ratio of GaS may be used as gallium sulfide.
The material mixed in this manner is put into a crucible formed by alumina etc., and is processed in an atmosphere of hydrogen sulfide at a temperature of 1000° C. for about three hours to be crystallized. Gas diluted with inert gas such as argon, nitrogen, or others to a few percent may be used as the hydrogen sulfide atmosphere. The crystallizing process may be performed in an atmosphere of inert gas such as argon and nitrogen.
Temperature in the crystallizing process may range from about 700° C. to 1400° C. depending upon the grain size and crystallinity of the material powder to be used.
An image display apparatus using the phosphor material of the present invention will now be described in detail.
Conventionally, the color display represented by CRT display combines three types of phosphors of three colors of red (R), green (G), and blue (B) to form a color image.
A display of high luminance and wide color gamut can be realized by using the above described phosphor formed using the phosphor material of the present invention for at least one type of phosphor. Specifically, a black matrix is formed on the face plate and the phosphor particle is formed through methods such as screen printing, similar to the phosphor for the conventional CRT display, the field emission display (FED), and the surface conduction emission display.
As shown in
The light-emitting member described above may also include an electrode to be applied with a predetermined potential. The electrode includes aluminum and ITO, and is formed through vapor deposition method and sputtering method.
For the phosphor material configuring each phosphor of red and blue, Y2O2S:Eu (red), CaS:Eu (red), ZnS:Ag, Al (blue), CaMgSi2O6:Eu (blue) etc., may be appropriately combined and used according to the display characteristics of the light-emitting member.
If Y2O2S:Eu is used for red, ZnS:Ag, Al is used for blue, and Ba0.1Sr0.9Ga2S4:Eu of the present invention is used, the display color gamut enhances by about 7% compared to the combination of three colors of the above red and blue phosphors, and green phosphor SrGa2S4:Eu conventionally used. In luminance, Ba0.1Sr0.9Ga2S4:Eu obtains higher luminance than SrGa2S4:Eu.
Regarding the optimum configuring ratio of BaxSr1-xGa2S4:Eu, the optimum composition ratio can be selected according to the combination of the phosphor materials of the other two colors to be used and the required luminance characteristic, and is preferably selected from 0.03≦X≦0.4.
The FED shown in
The display of
The present invention will be described in detail below using specific examples.
A phosphor material of the present invention was produced. Strontium sulfide powder (SrS), barium sulfide powder (BaS), gallium sulfide powder (Ga2S3), and europium chloride powder (EuCl3) were used as the material, and the respective powders were mixed using a mortar. The respective materials were weighed to meet the weight ratio of SrS:BaS:Ga2S3:EuCl3≅0.44:0.09:1:0.03 so that the host material has a composition represented by Ba0.1Sr0.9Ga2S4. The concentration of Eu was three atomic percent with respect to the molar concentration of Sr+Ba.
The powder was then put into a crucible made of alumina, arranged in an atmosphere of hydrogen sulfide gas diluted with argon to 2%, and subjected to a crystallizing process in the atmosphere of 1000° C. for two hours. The composition ratio of the powder of the phosphor material produced in the above manner was analyzed by X-ray fluorescent. As a result, it was confirmed to have obtained the phosphor material with the composition ratio of Ba:Sr:Ga:S:Eu=1.05:8.68:20.3:40.9:0.29 at molar ratio.
Subsequently, an evaluation was carried out on the light-emitting characteristic of the powder of the produced phosphor material. Luminance obtained by irradiating 0.1 gram powder with the electron beam having a current density of 1 mA/cm2 was 454 cd/m2. This luminance is approximately 1.30 times as high as that of the phosphor SrGa2S4:Eu produced at the same conditions. The emission color expressed by the CIE chromaticity coordinate was given by (x, y)=(0.265, 0.683).
A phosphor material different in composition ratio was produced through the same process as in Example 1. Strontium sulfide powder (SrS), barium sulfide powder (BaS), gallium sulfide powder (Ga2S3), and europium chloride powder (EuCl3) were used as the material. The materials were weighed to meet the weight ration of SrS:BaS:Ga2S3:EuCl3≅0.30:0.28:1:0.03 so that the host material has a composition represented by Ba0.4Sr0.6Ga2S4.
An evaluation was conducted on the light-emitting characteristic of the phosphor material obtained by the above process. Luminance obtained by irradiating 0.1 gram of powder with electron beam having a current density of 1 mA/cm2 was 363 cd/m2. This luminance is approximately 1.04 times as high as that of the SrGa2S4:Eu phosphor. The CIE chromaticity coordinate was (x, y)=(0.239, 0.663).
An image display apparatus was produced using the phosphor material produced in Example 1. The image display apparatus of the present example is the FED of
First, a method of producing a rear plate (electron source substrate) 20 will be described.
A 200 nm aluminum as the cathode electrode 9 was deposited on the glass substrate 8 by the sputtering method. A 600 nm of silicon dioxide was then deposited as the insulating layer 10 by the CVD method, and 100 nm of titanium film was deposited as the gate electrode 11 by the sputtering method.
The opening 12 with a diameter of 1 μm was formed in the gate electrode 11 and the insulating layer 10 by photolithography and etching process.
The substrate passed through the above production process was arranged in the sputtering device, the air in the device was evacuated and then molybdenum was deposited obliquely to form the electron-emitting portion 13 while the substrate 8 was being rotated. Subsequently, the unwanted molybdenum was removed by lift-off to form the electron-emitting portion 13. The rear plate 20 was formed by the above process. Description has been made of an area corresponding to one pixel, but actually, such configurations are arranged on the substrate in a matrix form.
A method of producing a face plate (fluorescent surface) 21 will now be described.
The black matrix 2 was formed on the glass substrate 14 (base member) by screen printing method to remove unnecessary light-emitting surface. An aperture was formed in a region to be formed with the phosphors 3, 4, 5 shown in
The powder of the phosphor material was dispersed in a binder etc. to form a paste, and the paste was applied to the aperture by screen printing method to form the fluorescent surface. The phosphor material used in this case is Y2O2S:Eu to form the red phosphor 3, ZnS:Ag, Cl to form the blue phosphor 4, and Ba0.1Sr0.9Ga2S4:Eu to form the phosphor 5. Ba0.1Sr0.9Ga2S4:Eu was produced at the same conditions as in Example 1.
After a filming process, a 100 nm aluminum as the metal back 19 was deposited through an evaporation method to form the face plate 21. Description has been made of an area corresponding to one pixel, but actually, such configurations are arranged on the substrate in a matrix form.
The rear plate 20 and the face plate 21 produced in the above manner were combined to produce the FED. The electron-emitting region 23 is arranged in a region where the cathode electrode 9 and the gate electrode 11 cross. Each of the plurality of electron-emitting regions 23 is arranged so as to correspond to each phosphor 3 to 5 shown in
High voltage terminal Hv is connected to the face plate 21. The application voltage is 10 kv.
Signal input terminals Dx1 to Dxm, and Dy1 to Dyn are connected to the cathode electrode 9 and the gate electrode 11, respectively, in the rear plate 20, where a signal from the drive driver is input to the respective terminal.
An FED forming an image by combining three colors of red (Y2O2S:Eu), green (SrGa2S4:Eu), and blue (ZnS:Ag, Al) of the prior art was produced for comparison.
The display color gamut of the display produced in the above manner is shown in the CIE chromaticity diagram of
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2007-116151, filed on Apr. 25, 2007, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-116151 | Apr 2007 | JP | national |
