Up-conversion phosphor

Abstract

To provide a novel up-conversion phosphor excellent in light-emitting properties, the up-conversion phosphor of the present invention is an up-conversion phosphor including, in a ZnMoO.sub.4-based matrix material thereof, Yb.sup.3+, at least one rare earth metal ion selected from the group consisting of Tm.sup.3+, Er.sup.3+ and Ho.sup.3+, and at least one monovalent metal ion selected from the group consisting of Li.sup.+, K.sup.+, Na.sup.+ and Rb.sup.+.

Claims

1. An up-conversion phosphor comprising, in a ZnMoO.sub.4-based matrix material thereof, Yb.sup.3+, at least one rare earth metal ion selected from the group consisting of Tm.sup.3+, Er.sup.3+ and Ho.sup.3+, and at least one monovalent metal ion selected from the group consisting of Li.sup.+, K.sup.+, Na.sup.+ and Rb.sup.+.

2. The up-conversion phosphor according to claim 1, wherein when the total content of the divalent metal ion in the matrix material, Yb.sup.3+, the rare earth metal ion and the monovalent metal ion is set at 100 at %, the content ratio of Yb.sup.3+ is 20 at % or less.

3. The up-conversion phosphor according to claim 1, wherein the rare earth metal ion is Tm.sup.3+, and when the total content of the divalent metal ion in the matrix material, Yb.sup.3+, the rare earth metal ion and the monovalent metal ion is set at 100 at %, the content ratio of Tm.sup.3+ is 2 at % or less.

4. The up-conversion phosphor according to claim 1, wherein the rare earth metal ion is Er.sup.3+, and when the total content of the divalent metal ion in the matrix material, Yb.sup.3+, the rare earth metal ion and the monovalent metal ion is set at 100 at %, the content ratio of Er.sup.3+ is 5 at % or less.

5. The up-conversion phosphor according to claim 1, wherein the rare earth metal ion is Ho.sup.3+, and when the total content of the divalent metal ion in the matrix material, Yb.sup.3+, the rare earth metal ion and the monovalent metal ion is set at 100 at %, the content ratio of Ho.sup.3+ is 5 at % or less.

6. The up-conversion phosphor according to claim 1, wherein when the total content of the divalent metal ion in the matrix material, Yb.sup.3+, the rare earth metal ion and the monovalent metal ion is set at 100 at %, the content ratio of the monovalent metal ion is 20 at % or less.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a chart showing the XDR spectra of the samples of Examples 1, 75 and 79.

(2) FIG. 2 is the scanning electron microscope (SEM) image of the sample of Example 1.

(3) FIG. 3 is a graph showing the light emission spectra, in the wavelength region from 450 to 510 nm, of the samples of Examples 1 to 7.

(4) FIG. 4 is a graph showing the light emission spectra, in the wavelength region from 750 to 850 nm, of the samples of Examples 1 to 7.

(5) FIG. 5 is a graph showing the light emission spectra, in the wavelength region from 450 to 510 nm, of the samples of Examples 1 and 8 to 12, and Comparative Example 1.

(6) FIG. 6 is a graph showing the light emission spectra, in the wavelength region from 750 to 850 nm, of the samples of Examples 1 and 8 to 12, and Comparative Example 1.

(7) FIG. 7 is a graph showing the light emission spectra, in the wavelength region from 450 to 510 nm, of the samples of Examples 1 and 13 to 15, and Comparative Example 2.

(8) FIG. 8 is a graph showing the light emission spectra, in the wavelength region from 750 to 850 nm, of the samples of Examples 1 and 13 to 15, and Comparative Example 2.

(9) FIG. 9 is a graph showing the light emission spectra, in the wavelength region from 450 to 510 nm, of the samples of Examples 1 and 16 to 20, and Comparative Example 2.

(10) FIG. 10 is a graph showing the light emission spectra, in the wavelength region from 750 to 850 nm, of the samples of Examples 1 and 16 to 20, and Comparative Example 2.

(11) FIG. 11 is a graph showing the light emission spectra of the samples of Examples 21 to 26, and Comparative Example 3.

(12) FIG. 12 is a graph showing the light emission spectra of the samples of Examples 21 and 27 to 31, and Comparative Example 4.

(13) FIG. 13 is a graph showing the light emission spectra of the samples of Examples 21 and 32 to 34, and Comparative Example 5.

(14) FIG. 14 is a graph showing the light emission spectra of the samples of Examples 21 and 35 to 38, and Comparative Example 5.

(15) FIG. 15 is a graph showing the light emission spectra of the samples of Examples 39 to 46.

(16) FIG. 16 is a graph showing the light emission spectra of the samples of Examples 41 and 47 to 51, and Comparative Example 6.

(17) FIG. 17 is a graph showing the light emission spectra of the samples of Examples 41 and 52 to 54, and Comparative Example 7.

(18) FIG. 18 is a graph showing the light emission spectra of the samples of Examples 41 and 55 to 58, and Comparative Example 7.

(19) FIG. 19 is a graph showing the light emission spectra of the samples of Examples 59 to 62.

(20) FIG. 20 is a graph showing the light emission spectra of the samples of Examples 63 to 65.

(21) FIG. 21 is a graph showing the light emission spectra of the samples of Examples 66 to 68.

(22) FIG. 22 is a graph showing the light emission spectra of the samples of Examples 69 to 74.

(23) FIG. 23 is a graph showing the light emission spectra, in the wavelength region from 450 to 510 nm, of the samples of Examples 1 and 75 to 79.

(24) FIG. 24 is a graph showing the light emission spectra, in the wavelength region from 620 to 680 nm, of the samples of Examples 1 and 75 to 79.

(25) FIG. 25 is a graph showing the light emission spectra, in the wavelength region from 750 to 850 nm, of the samples of Examples 1 and 75 to 79.

DESCRIPTION OF EMBODIMENTS

(26) Hereinafter, the up-conversion phosphor according to the present invention is described in detail, but the scope of the present invention is not restricted by these descriptions and the cases other than the cases shown below as examples can also be embodied by appropriately modifying within a scope not impairing the gist of the present invention.

(27) [Up-Conversion Phosphor]

(28) The matrix material of the up-conversion phosphor of the present invention is a ZnMoO.sub.4-based matrix material.

(29) Here, in the present invention, the “ZnMoO.sub.4-based matrix material” includes matrix materials in which in addition to ZnMoO.sub.4, within a limit not essentially altering the properties of the matrix material, a fraction of Zn in ZnMoO.sub.4 is substituted with another equivalent element such as Ca.

(30) Specifically, for example, the ratio between Zn and the other equivalent element preferably falls, in terms of the number to atoms, within a range of Zn:other equivalent element=100:0 to 80:20.

(31) The up-conversion phosphor of the present invention is constituted by including the following specific ions in this matrix material.

(32) In the up-conversion phosphor of the present invention, the following specific ions are all inferred to substitute for Zn.sup.2+ in the matrix material.

(33) [Yb.sup.3+]

(34) Yb.sup.3+ is included in the up-conversion phosphor of the present invention.

(35) When the total content of the divalent metal ion in the matrix material, Yb.sup.3+, the rare earth metal ion and the monovalent metal ion is set at 100 at %, the content ratio of Yb.sup.3+ (hereinafter, sometimes simply referred to as “the content ratio of Yb.sup.3+”) is preferably 20 at % or less and more preferably 5 to 15 at %.

(36) Here, “the divalent metal ion in the matrix material” in the foregoing description means Zn.sup.2+ when the matrix material is ZnMoO.sub.4, and means Zn.sup.2+ and the equivalent ion (such as Ca.sup.2+) when the matrix material is the material in which a fraction of Zn in ZnMoO.sub.4 is substituted with another equivalent element (such as Ca). With respect to the content ratio of the below-described rare earth metal ion and the content ratio of the below-described monovalent metal ion, “the divalent metal ion in the matrix material” has the same meaning.

(37) As described above, the content ratio of Yb.sup.3+ is described to be preferably 20 at % or less; however, because Yb.sup.3+ is an essential component, needless to say, the case where the content ratio of Yb.sup.3+ is 0 at % is not involved. The same description is applicable to the descriptions on other essential components.

(38) [Rare Earth Metal Ion]

(39) The up-conversion phosphor of the present invention includes at least one rare earth metal ion selected from the group consisting of Tm.sup.3+, Er.sup.3+ and Ho.sup.3+.

(40) When the rare earth metal ion is Tm.sup.3+, the up-conversion phosphor exhibits blue-based light emission.

(41) When the total content of the divalent metal ion in the matrix material, Yb.sup.3+, the rare earth metal ion and the monovalent metal ion is set at 100 at %, the content ratio of Tm.sup.3+ (hereinafter, sometimes simply referred to as “the content ratio of Tm.sup.3+”) is preferably 2 at % or less, more preferably within a range from 0.05 to 1 at % and particularly preferably within a range from 0.05 to 0.5 at %.

(42) When the rare earth metal ion is Er.sup.3+, the up-conversion phosphor exhibits green-based light emission.

(43) When the total content of the divalent metal ion in the matrix material, Yb.sup.3+, the rare earth metal ion and the monovalent metal ion is set at 100 at %, the content ratio of Er.sup.3+ (hereinafter, sometimes simply referred to as “the content ratio of Er.sup.3+”) is preferably 5 at % or less, more preferably within a range from 0.1 to 2 at % and particularly preferably within a range from 0.2 to 0.6 at %.

(44) When the rare earth metal ion is Ho.sup.3+, the up-conversion phosphor exhibits red-based light emission.

(45) When the total content of the divalent metal ion in the matrix material, Yb.sup.3+, the rare earth metal ion and the monovalent metal ion is set at 100 at %, the content ratio of Ho.sup.3+ (hereinafter, sometimes simply referred to as “the content ratio of Ho.sup.3+”) is preferably 5 at % or less, more preferably 2 at % or less and particularly preferably within a range from 0.03 to 1 at %.

(46) The matrix material can include a plurality of the rare earth metal ions in combination.

(47) Such a combination of a plurality of the rare earth metal ions enables to obtain up-conversion light emission having a color not to be obtained by applying Tm.sup.3+, Er.sup.3+ or Ho.sup.3+ each alone.

(48) In such a case, an intended light-emitting color can be obtained by appropriately selecting the mutual ratio in the combination of the plurality of the rare earth metal ions.

(49) When white-based light emission is obtained, it is advantageous to combine Tm.sup.3+ and Ho.sup.3+ as the rare earth metal ions.

(50) [Monovalent Metal Ion]

(51) The up-conversion phosphor of the present invention includes at least one monovalent metal ion selected from the group consisting of Li.sup.+, K.sup.+, Na.sup.+ and Rb.sup.+.

(52) In particular, the use of K.sup.+ or Na.sup.+ results in excellent light-emitting properties, and the use of K.sup.+ is particularly preferable.

(53) When the total content of the divalent metal ion in the matrix material, Yb.sup.3+, the rare earth metal ion and the monovalent metal ion is set at 100 at %, the content ratio of the monovalent metal ion (hereinafter, sometimes simply referred to as, for example, “the content ratio of the monovalent metal ion”, “the content ratio of Li.sup.+” or the like) is preferably 20 at % or less and more preferably within a range from 5 to 15 at %.

(54) [Method for Producing Up-Conversion Phosphor]

(55) The up-conversion phosphor of the present invention can be produced by using a mixture of the compounds containing the above-described components and by applying, for example, a heretofore known solid phase method or liquid phase method (such as a sol-gel method).

(56) For example, the up-conversion phosphor of the present invention is preferably produced as follows, without being particularly limited.

(57) First, the compounds (for example, oxides and carbonates) containing the elements constituting the up-conversion phosphor is mixed.

(58) The mixture may include a flux.

(59) Examples of the flux include: Li.sub.2CO.sub.3, H.sub.3BO.sub.3, NH.sub.4F, CaF.sub.2, MgF.sub.2, B.sub.2O.sub.3 and (NH.sub.4).sub.2CO.sub.3; among these, Li.sub.2CO.sub.3, H.sub.3BO.sub.3 and NH.sub.4F are preferable.

(60) The mixing method may be either dry mixing or wet mixing, without being particularly limited; a wet mixing performed by adding ethanol, water or the like is preferably quoted. It is to be noted that in the case of wet mixing, drying is appropriately performed after mixing.

(61) The mixing proportions of the components can be appropriately determined in consideration of the content ratios of the components in the up-conversion phosphor.

(62) When a flux is added, the mixing proportion of the flux is preferably within a range from 0.005 to 0.4 mol.

(63) Next, the mixture obtained as described above is burned.

(64) The burning is performed in an air atmosphere, preferably in a temperature range from 500 to 800° C. and more preferably in a temperature range from 550 to 700° C.

(65) The burning time is preferably 3 to 5 hours.

(66) After burning, the burned mixture may be pulverized into powder, and is preferably pulverized into powder of the order of a few nanometers to several tens nanometers.

EXAMPLES

(67) Hereinafter, the up-conversion phosphor according to the present invention is described in detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1

(68) Powders of ZnCO.sub.3; 0.433 g, MoO.sub.3; 0.9596 g, TmCl.sub.3.6H.sub.2O; 0.0026 g, Yb.sub.2O.sub.3; 0.134 g, and K.sub.2CO.sub.3; 0.046 g were used, and were wet mixed in a mortar with a pestle by using ethanol.

(69) After the mixing, the resulting mixture was dried at 130° C. for 4 hours, and pulverized with a pestle to yield a mixed powder.

(70) Next, the resulting mixed powder was molded with a twin screw extruder into a pellet (Φ13×3 mm), and the pellet was burned in an air atmosphere at 650° C. for 4 hours (heating rate: 5° C./min).

(71) The pellet after burning was finely pulverized with a vibration mill.

(72) Thus, as the sample according to Example 1, there was obtained a powder represented by ZnMoO.sub.4:Yb.sup.3+,Tm.sup.3+,K.sup.+, and having content ratios of 10 at %, 0.1 at % and 10 at % for Yb.sup.3+, Tm.sup.3+ and K.sup.+, respectively.

Examples 2 to 7

(73) As each of the samples according to Examples 2 to 7, a powder represented by ZnMoO.sub.4:Yb.sup.3+,Tm.sup.3+,K.sup.+ and having the content ratios of Yb.sup.3+, Tm.sup.3+ and K.sup.+ as shown in Table 1 presented below was obtained in the same manner as in Example 1 except that the powder used as the raw material was altered as shown in Table 1 presented below.

(74) TABLE-US-00001 TABLE 1 Example Example Example Example Example Example 2 3 4 5 6 7 Amounts ZnO 0.4337 0.4328 0.432 0.43 0.431 0.428 used of raw MoO.sub.3 0.9596 0.9596 0.9596 0.9596 0.9596 0.9596 material Yb.sub.2O.sub.3 0.131 0.131 0.131 0.131 0.131 0.131 powders (g) TmCl.sub.3•6H.sub.2O 0.0013 0.0054 0.008 0.0107 0.0134 0.0267 K.sub.2CO.sub.3 0.046 0.046 0.046 0.046 0.046 0.046 Content Yb.sup.3+ 10 10 10 10 10 10 ratios of Tm.sup.3− 0.05 0.2 0.3 0.4 0.5 1 ions (at %) K.sup.| 10 10 10 10 10 10

Examples 8 to 12 and Comparative Example 1

(75) As each of the samples according to Examples 8 to 12, a powder represented by ZnMoO.sub.4:Yb.sup.3+,Tm.sup.3+,K.sup.+ and having the content ratios of Yb.sup.3+, Tm.sup.3+ and K.sup.+ as shown in Table 2 presented below was obtained in the same manner as in Example 1 except that the powder used as the raw material was altered as shown in Table 2 presented below.

(76) Similarly, as the sample according to Comparative Example 1, a powder represented by ZnMoO.sub.4:Tm.sup.3+,K.sup.+ and having the content ratios of Tm.sup.3+ and K.sup.+ as shown in Table 2 presented below was obtained.

(77) TABLE-US-00002 TABLE 2 Example Example Example Example Example Comparative 8 9 10 11 12 Example 1 Amounts ZnCO.sub.3 0.46 0.44 0.412 0.406 0.379 0.487 used of raw MoO.sub.3 0.9596 0.9596 0.9596 0.9596 0.9596 0.9596 material Yb.sub.2O.sub.3 0.066 0.099 0.165 0.197 0.263 — powders (g) TmCl.sub.3•6H.sub.2O 0.0026 0.0026 0.0026 0.0026 0.0026 0.0026 K.sub.2CO.sub.3 0.046 0.046 0.046 0.046 0.046 0.046 Content Yb.sup.3+ 5 7.5 12.5 15 20 — ratios of Tm.sup.3 0.1 0.1 0.1 0.1 0.1 0.1 ions (at %) K.sup.+ 10 10 10 10 10 10

Examples 13 to 15 and Comparative Example 2

(78) As each of the samples according to Examples 13 to 15, a powder represented by ZnMoO.sub.4:Yb.sup.3+,Tm.sup.3+,M.sup.+ and having the content ratios of Yb.sup.3+, Tm.sup.3+ and M.sup.+ as shown in Table 3 presented below was obtained in the same manner as in Example 1 except that the powder used as the raw material was altered as shown in Table 3 presented below. It is to be noted that M.sup.+ represents any of K.sup.+, Na.sup.+, Li.sup.+ and Rb.sup.+.

(79) Similarly, as the sample according to Comparative Example 2, a powder represented by ZnMoO.sub.4:Yb.sup.3+,Tm.sup.3+ and having the content ratios of Yb.sup.3+ and Tm.sup.3+ as shown in Table 3 presented below was obtained.

(80) TABLE-US-00003 TABLE 3 Example Example Example Comparative 13 14 15 Example 2 Amounts used of ZnCO.sub.3 0.433 0.433 0.433 0.487 raw material MoO.sub.3 0.9596 0.9596 0.9596 0.9596 powders (g) Yb.sub.2O.sub.3 0.134 0.134 0.134 0.134 TmCl.sub.3•6H.sub.2O 0.0026 0.0026 0.0026 0.0026 K.sub.2CO.sub.3 — — — — Na.sub.2CO.sub.3 0.0354 — — — Li.sub.2CO.sub.3 — 0.025 — — Rb.sub.2CO.sub.3 — — 0.077 — Content ratios Yb.sup.3+ 10 10 10 10 of ions (at %) Tm.sup.3− 0.1 0.1 0.1 0.1 K.sup.+ — — — — Na.sup.| 10 — — — Li — 10 — — Rb.sup.| — — 10 —

Examples 16 to 20

(81) As each of the samples according to Examples 16 to 20, a powder represented by ZnMoO.sub.4:Yb.sup.3+,Tm.sup.3+,K.sup.+ and having the content ratios of Yb.sup.3+, Tm.sup.3+ and K.sup.+ as shown in Table 4 presented below was obtained in the same manner as in Example 1 except that the powder used as the raw material was altered as shown in Table 4 presented below.

(82) TABLE-US-00004 TABLE 4 Example Example Example Example Example 16 17 18 19 20 Amounts ZnCO.sub.3 0.46 0.44 0.412 0.406 0.379 used of raw MoO.sub.3 0.9596 0.9596 0.9596 0.9596 0.9596 material Yb.sub.2O.sub.3 0.134 0.134 0.134 0.134 0.134 powders (g) TmCl.sub.3•6H.sub.2O 0.0026 0.0026 0.0026 0.0026 0.0026 K.sub.2CO.sub.3 0.023 0.035 0.058 0.069 0.092 Content Yb.sup.3− 10 10 10 10 10 ratios of Tm.sup.3| 0.1 0.1 0.1 0.1 0.1 ions (at %) K.sup.− 5 7.5 12.5 15 20

Examples 21 to 26 and Comparative Example 3

(83) As each of the samples according to Examples 21 to 26, a powder represented by ZnMoO.sub.4:Yb.sup.3+,Er.sup.3+,K.sup.+ and having the content ratios of Yb.sup.3+, Er.sup.3+ and K.sup.+ as shown in Table 5 presented below was obtained in the same manner as in Example 1 except that the powder used as the raw material was altered as shown in Table 5 presented below.

(84) Similarly, as the sample according to Comparative Example 3, a powder represented by ZnMoO.sub.4:Yb.sup.3+,K.sup.+ and having the content ratios of Yb.sup.3+ and K.sup.+ as shown in Table 5 presented below was obtained.

(85) TABLE-US-00005 TABLE 5 Example Example Example Example Example Example Comparative 21 22 23 24 25 26 Example 3 Amounts ZnCO.sub.3 0.433 0.4328 0.4323 0.4312 0.428 0.423 0.434 used of raw MoO.sub.3 0.9596 0.9596 0.9596 0.9596 0.9596 0.9596 0.9596 material Yb.sub.2O.sub.3 0.0134 0.0134 0.0134 0.0134 0.0134 0.0134 0.0134 powders (g) Er(NO.sub.3).sub.3•5H.sub.2O 0.0029 0.0059 0.0088 0.0148 0.0296 0.0592 — K.sub.2CO.sub.3 0.046 0.046 0.046 0.046 0.046 0.046 0.046 Content Yb.sup.3+ 10 10 10 10 10 10 10 ratios of Er.sup.3 0.1 0.2 0.3 0.5 1 2 — ions (at %) K.sup.+ 10 10 10 10 10 10 10

Examples 27 to 31 and Comparative Example 4

(86) As each of the samples according to Examples 27 to 31, a powder represented by ZnMoO.sub.4:Yb.sup.3+,Er.sup.3+,K.sup.+ and having the content ratios of Yb.sup.3+, Er.sup.3+ and K.sup.+ as shown in Table 6 presented below was obtained in the same manner as in Example 1 except that the powder used as the raw material was altered as shown in Table 6 presented below.

(87) Similarly, as the sample according to Comparative Example 4, a powder represented by ZnMoO.sub.4:Er.sup.3+,K.sup.+ and having the content ratios of Er.sup.3+ and K.sup.+ as shown in Table 6 presented below was obtained.

(88) TABLE-US-00006 TABLE 6 Example Example Example Example Example Comparative 27 28 29 30 31 Example 4 Amounts ZnCO.sub.3 0.46 0.455 0.44 0.412 0.406 0.433 used of raw MoO.sub.3 0.9596 0.9596 0.9596 0.9596 0.9596 0.9596 material Yb.sub.2O.sub.3 0.066 0.0792 0.099 0.165 0.197 — powders (g) Er(NO.sub.3).sub.3•5H.sub.2O 0.0029 0.0029 0.0029 0.0029 0.0029 0.0029 K.sub.2CO.sub.3 0.046 0.046 0.046 0.046 0.046 0.046 Content Yb.sup.3− 5 6 7.5 12.5 15 — ratios of Er.sup.3+ 0.1 0.1 0.1 0.1 0.1 0.1 ions (at %) K.sup.+ 10 10 10 10 10 10

Examples 32 to 34 and Comparative Example 5

(89) As each of the samples according to Examples 32 to 34, a powder represented by ZnMoO.sub.4:Yb.sup.3+,Er.sup.3+,M.sup.+ and having the content ratios of Yb.sup.3+, Er.sup.3+ and M.sup.+ as shown in Table 7 presented below was obtained in the same manner as in Example 1 except that the powder used as the raw material was altered as shown in Table 7 presented below. It is to be noted that M.sup.+ represents any of K.sup.+, Na.sup.+, Li.sup.+ and Rb.sup.+.

(90) Similarly, as the sample according to Comparative Example 5, a powder represented by ZnMoO.sub.4:Yb.sup.3+,Er.sup.3+ and having the content ratios of Yb.sup.3+ and Er.sup.3+ as shown in Table 7 presented below was obtained.

(91) TABLE-US-00007 TABLE 7 Example Example Example Comparative 32 33 34 Example 5 Amounts used of ZnCO.sub.3 0.433 0.433 0.433 0.487 raw material MoO.sub.3 0.9596 0.9596 0.9596 0.9596 powders (g) Yb.sub.2O.sub.3 0.134 0.134 0.134 0.134 Er(NO.sub.3).sub.3•5H.sub.2O 0.0029 0.0029 0.0029 0.0029 K.sub.2CO.sub.3 — — — — Na.sub.2CO.sub.3 0.0354 — — — Li.sub.2CO.sub.3 — 0.025 — — Rb.sub.2CO.sub.3 — — 0.077 — Content ratios Yb.sup.3| 10 10 10 10 of ions (at %) Er.sup.3| 0.1 0.1 0.1 0.1 K.sup.+ — — — — Na.sup.− 10 — — — Li.sup.− — 10 — — Rb.sup.− — — 10 —

Examples 35 to 38

(92) As each of the samples according to Examples 35 to 38, a powder represented by ZnMoO.sub.4:Yb.sup.3+,Er.sup.3+,K.sup.+ and having the content ratios of Yb.sup.3+, Er.sup.3+ and K.sup.+ as shown in Table 8 presented below was obtained in the same manner as in Example 1 except that the powder used as the raw material was altered as shown in Table 8 presented below.

(93) TABLE-US-00008 TABLE 8 Example Example Example Example 35 36 37 38 Amounts used of ZnCO.sub.3 0.46 0.44 0.412 0.406 raw material MoO.sub.3 0.9596 0.9596 0.9596 0.9596 powders (g) Yb.sub.2O.sub.3 0.134 0.134 0.134 0.134 Er(NO.sub.3).sub.3•5H.sub.2O 0.0029 0.0029 0.0029 0.0029 K.sub.2CO.sub.3 0.023 0.035 0.058 0.069 Content ratios Yb.sup.3+ 10 10 10 10 of ions (at %) Er.sup.3| 0.1 0.1 0.1 0.1 K.sup.+ 5 7.5 12.5 15

Examples 39 to 46

(94) As each of the samples according to Examples 39 to 46, a powder represented by ZnMoO.sub.4:Yb.sup.3+,Ho.sup.3+,K.sup.+ and having the content ratios of Yb.sup.3+, Ho.sup.3+ and K.sup.+ as shown in Table 9 presented below was obtained in the same manner as in Example 1 except that the powder used as the raw material was altered as shown in Table 9 presented below.

(95) TABLE-US-00009 TABLE 9 Example Example Example Example Example Example Example Example 39 40 41 42 43 44 45 46 Amounts ZnCO.sub.3 0.434 0.4337 0.433 0.4328 0.432 0.431 0.428 0.423 used of raw MoO.sub.3 0.9596 0.9596 0.9596 0.9596 0.9596 0.9596 0.9596 0.9596 material Yb.sub.2O.sub.3 0.134 0.134 0.134 0.134 0.134 0.134 0.134 0.134 powders (g) Ho(NO.sub.3).sub.3•5H.sub.2O 0.0015 0.0015 0.0029 0.0059 0.0078 0.015 0.0296 0.06 K.sub.2CO.sub.3 0.046 0.046 0.046 0.046 0.046 0.046 0.046 0.046 Content Yb.sup.3+ 10 10 10 10 10 10 10 10 ratios of Ho.sup.3− 0.03 0.05 0.1 0.2 0.3 0.5 1 2 ions (at %) K.sup.− 10 10 10 10 10 10 10 10

Examples 47 to 51 and Comparative Example 6

(96) As each of the samples according to Examples 47 to 51, a powder represented by ZnMoO.sub.4:Yb.sup.3+,Ho.sup.3+,K.sup.+ and having the content ratios of Yb.sup.3+, Ho.sup.3+ and K.sup.+ as shown in Table 10 presented below was obtained in the same manner as in Example 1 except that the powder used as the raw material was altered as shown in Table 10 presented below.

(97) Similarly, as the sample according to Comparative Example 6, a powder represented by ZnMoO.sub.4:Ho.sup.3+,K.sup.+ and having the content ratios of Ho.sup.3+ and K.sup.+ as shown in Table 10 presented below was obtained.

(98) TABLE-US-00010 TABLE 10 Example Example Example Example Example Comparative 47 48 49 50 51 Example 6 Amounts ZnCO.sub.3 0.46 0.44 0.412 0.406 0.379 0.487 used of raw MoO.sub.3 0.9596 0.9596 0.9596 0.9596 0.9596 0.9596 material Yb.sub.2O.sub.3 0.066 0.099 0.165 0.197 0.263 — powders (g) Ho(NO.sub.3).sub.3•5H.sub.2O 0.0029 0.0029 0.0029 0.0029 0.0029 0.0029 K.sub.2CO.sub.3 0.046 0.046 0.046 0.046 0.046 0.046 Content Yb.sup.3− 5 7.5 12.5 15 20 — ratios of Ho.sup.3| 0.1 0.1 0.1 0.1 0.1 0.1 ions (at %) K.sup.+ 10 10 10 10 10 10

Examples 52 to 54 and Comparative Example 7

(99) As each of the samples according to Examples 52 to 54, a powder represented by ZnMoO.sub.4:Yb.sup.3+,Ho.sup.3+,M.sup.+ and having the content ratios of Yb.sup.3+, Ho.sup.3+ and M.sup.+ as shown in Table 11 presented below was obtained in the same manner as in Example 1 except that the powder used as the raw material was altered as shown in Table 11 presented below. It is to be noted that M.sup.+ represents any of K.sup.+, Na.sup.+, Li.sup.+ and Rb.sup.+.

(100) Similarly, as the sample according to Comparative Example 7, a powder represented by ZnMoO.sub.4:Yb.sup.3+,Ho.sup.3+ and having the content ratios of Yb.sup.3+ and Ho.sup.3+ as shown in Table 11 presented below was obtained.

(101) TABLE-US-00011 TABLE 11 Example Example Example Comparative 52 53 54 Example 7 Amounts used of ZnCO.sub.3 0.433 0.433 0.433 0.487 raw material MoO.sub.3 0.9596 0.9596 0.9596 0.9596 powders (g) Yb.sub.2O.sub.3 0.134 0.134 0.134 0.134 Ho(NO.sub.3).sub.3•5H.sub.2O 0.0029 0.0029 0.0029 0.0029 K.sub.2CO.sub.3 — — — — Na.sub.2CO.sub.3 0.0354 — — — Li.sub.2CO.sub.3 — 0.025 — — Rb.sub.2CO.sub.3 — — 0.077 — Content ratios Yb.sup.3+ 10 10 10 10 of ions (at %) Ho.sup.3+ 0.1 0.1 0.1 0.1 K.sup.+ — — — — Na 10 — — — Li — 10 — — Rb.sup.| — — 10 —

Examples 55 to 58

(102) As each of the samples according to Examples 55 to 58, a powder represented by ZnMoO.sub.4:Yb.sup.3+,Ho.sup.3+,K.sup.+ and having the content ratios of Yb.sup.3+, Ho.sup.3+ and K.sup.+ as shown in Table 12 presented below was obtained in the same manner as in Example 1 except that the powder used as the raw material was altered as shown in Table 12 presented below.

(103) TABLE-US-00012 TABLE 12 Example Example Example Example 55 56 57 58 Amounts used of ZnCO.sub.3 0.46 0.44 0.412 0.406 raw material MoO.sub.3 0.9596 0.9596 0.9596 0.9596 powders (g) Yb.sub.2O.sub.3 0.134 0.134 0.134 0.134 Ho(NO.sub.3).sub.3•5H.sub.2O 0.0029 0.0029 0.0029 0.0029 K.sub.2CO.sub.3 0.023 0.0345 0.0575 0.069 Content ratios Yb.sup.3+ 10 10 10 10 of ions (at %) Ho.sup.3| 0.1 0.1 0.1 0.1 K.sup.+ 5 7.5 12.5 15

Examples 59 to 62

(104) As each of the samples according to Examples 59 to 62, a powder represented by ZnMoO.sub.4:Yb.sup.3+,Tm.sup.3+,Ho.sup.3+,K.sup.+ and having the content ratios of Yb.sup.3+, Tm.sup.3+, Ho.sup.3+ and K.sup.+ as shown in Table 13 presented below was obtained in the same manner as in Example 1 except that the powder used as the raw material was altered as shown in Table 13 presented below.

(105) TABLE-US-00013 TABLE 13 Example Example Example Example 59 60 61 62 Amounts used of ZnCO.sub.3 0.4334 0.4331 0.4334 0.4331 raw material MoO.sub.3 0.9596 0.9596 0.9596 0.9596 powders (g) Yb.sub.2O.sub.3 0.131 0.131 0.131 0.131 TmCl.sub.3•6H.sub.2O 0.0013 0.0013 0.0027 0.0027 Er(NO.sub.3).sub.3•5H.sub.2O — — — — Ho(NO.sub.3).sub.3•5H.sub.2O 0.0015 0.0029 0.0029 0.0015 K.sub.2CO.sub.3 0.046 0.046 0.046 0.046 Content ratios Yb.sup.3| 10 10 10 10 of ions (at %) Tm.sup.3| 0.05 0.05 0.1 0.1 Er.sup.3+ — — — — Ho.sup.3− 0.05 0.1 0.1 0.05 K.sup.− 10 10 10 10

Examples 63 to 65

(106) As each of the samples according to Examples 63 to 65, a powder represented by ZnMoO.sub.4:Yb.sup.3+,Tm.sup.3+,Er.sup.3+,K.sup.+ and having the content ratios of Yb.sup.3+, Tm.sup.3+, Er.sup.3+ and K.sup.+ as shown in Table 14 presented below was obtained in the same manner as in Example 1 except that the powder used as the raw material was altered as shown in Table 14 presented below.

(107) TABLE-US-00014 TABLE 14 Example Example Example 63 64 65 Amounts used of ZnCO.sub.3 0.4334 0.433 0.428 raw material MoO.sub.3 0.9596 0.9596 0.9596 powders (g) Yb.sub.2O.sub.3 0.131 0.131 0.131 TmCl.sub.3•6H.sub.2O 0.0027 0.0027 0.0027 Er(NO.sub.3).sub.3•5H.sub.2O 0.0029 0.0058 0.029 Ho(NO.sub.3).sub.3•5H.sub.2O — — — K.sub.2CO.sub.3 0.046 0.046 0.046 Content ratios Yb.sup.3 10 10 10 of ions (at %) Tm.sup.3+ 0.1 0.1 0.1 Er.sup.3| 0.1 0.2 1 Ho.sup.3− — — — K.sup.− 10 10 10

Examples 66 to 68

(108) As each of the samples according to Examples 66 to 68, a powder represented by ZnMoO.sub.4:Yb.sup.3+,Er.sup.3+,Ho.sup.3+,K.sup.+ and having the content ratios of Yb.sup.3+, Er.sup.3+, Ho.sup.3+ and K.sup.+ as shown in Table 15 presented below was obtained in the same manner as in Example 1 except that the powder used as the raw material was altered as shown in Table 15 presented below.

(109) TABLE-US-00015 TABLE 15 Example Example Example 66 67 68 Amounts used of ZnCO.sub.3 0.4323 0.4323 0.432 raw material MoO.sub.3 0.9596 0.9596 0.9596 powders (g) Yb.sub.2O.sub.3 0.131 0.131 0.131 TmCl.sub.3•6H.sub.2O — — — Er(NO.sub.3).sub.3•5H.sub.2O 0.0029 0.0058 0.0058 Ho(NO.sub.3).sub.3•5H.sub.2O 0.0059 0.0029 0.0059 K.sub.2CO.sub.3 0.046 0.046 0.046 Content ratios Yb.sup.3| 10 10 10 of ions (at %) Tm.sup.3− — — — Er.sup.3+ 0.1 0.2 0.2 Ho.sup.3+ 0.2 0.1 0.2 K.sup.+ 10 10 10

Examples 69 to 74

(110) As each of the samples according to Examples 69 to 74, a powder represented by ZnMoO.sub.4:Yb.sup.3+,Tm.sup.3+,Er.sup.3+,Ho.sup.3+,K.sup.+ and having the content ratios of Yb.sup.3+, Tm.sup.3+, Er.sup.3+, Ho.sup.3+ and K.sup.+ as shown in Table 16 presented below was obtained in the same manner as in Example 1 except that the powder used as the raw material was altered as shown in Table 16 presented below.

(111) TABLE-US-00016 TABLE 16 Example Example Example Example Example Example 69 70 71 72 73 74 Amounts ZnCO.sub.3 0.4332 0.433 0.4328 0.4331 0.4323 0.432 used of raw MoO.sub.3 0.9596 0.9596 0.9596 0.9596 0.9596 0.9596 material Yb.sub.2O.sub.3 0.131 0.131 0.131 0.131 0.131 0.131 powders (g) TmCl.sub.3•6H.sub.2O 0.0013 0.0013 0.0013 0.0027 0.0027 0.0054 Er(NO.sub.3).sub.3•5H.sub.2O 0.0001 0.0003 0.003 0.0003 0.003 0.006 Ho(NO.sub.3).sub.3•5H.sub.2O 0.0015 0.0015 0.0015 0.0015 0.0029 0.0059 K.sub.2CO.sub.3 0.046 0.046 0.046 0.046 0.046 0.046 Content Yb.sup.3+ 10 10 10 10 10 10 ratios of Tm.sup.3+ 0.05 0.05 0.05 0.1 0.1 0.2 ions (at %) Er.sup.3| 0.005 0.01 0.1 0.01 0.1 0.2 Ho.sup.3 0.05 0.05 0.05 0.05 0.1 0.2 K.sup.− 10 10 10 10 10 10

Examples 75 to 79

(112) As the samples according to Examples 75 to 79, powders represented by ZnMoO.sub.4:Yb.sup.3+,Tm.sup.3+,K.sup.+ and having the content ratios of Yb.sup.3+, Tm.sup.3+ and K.sup.+ of 10 at %, 0.1 at % and 10 at %, respectively were obtained in the same manner as in Example 1 except that the burning temperatures of the pellets were altered to 550° C., 600° C., 700° C., 750° C. and 800° C. in Examples 75 to 79, respectively.

(113) [Physical Property Evaluation 1: Identification of Sample]

(114) Crystal phase identification was performed by XRD for each of the samples of foregoing Examples 1, 75 and 79. As an X-ray diffractometer, “XRD-6300” manufactured by Shimadzu Corp. was used and CuKα was employed. The results thus obtained are shown in FIG. 1.

(115) For the sample of Example 1, a scanning electron microscope (SEM) image is shown in FIG. 2.

(116) From the results shown in FIGS. 1 and 2, by the operations shown in each of above-described Examples, the target up-conversion phosphors were verified to be obtained as fine powder forms.

(117) [Physical Property Evaluation 2: Light-Emitting Properties]

(118) For each of the samples according to foregoing Examples and Comparative Examples, the light emission spectrum observed by irradiation of the sample with 980-nm laser light was measured with “USB 4000 UV/VIS/NIR” (miniature optical fiber spectrophotometer, manufactured by Ocean Optics, Inc.). The measurement was performed at room temperature.

(119) The results thus obtained are as shown in FIGS. 3 to 25.

(120) Hereinafter, on the results shown in FIGS. 3 to 25, the overall considerations are shown (the following (1)), and then specific considerations (the following (2) to (6)) are shown on the effects due to, for example, the types and contents of the respective components on the light-emitting properties.

(121) (1) Overall Considerations

(122) In the samples of Examples 1 to 20 and 75 to 79 in which Yb.sup.3+ was added as the rare earth metal ion, peaks were found around 480 nm and 800 nm.

(123) In these samples, the light-emitting color observed by the human visual sense was blue, and this is inferred to be due to the light emission corresponding to the peaks around 480 nm. The peaks around 800 nm correspond to near infrared light emission, fall in the wavelength region outside the visible region, and accordingly are not observed by the visible human sense.

(124) In the samples of Examples 21 to 38 in which Er.sup.3+ was added as the rare earth metal ion, peaks were found around 520 to 565 nm and 630 to 670 nm.

(125) In these samples, the light-emitting color observed by the human visual sense was bright green, this is mainly due to the light emission corresponding to the peaks around 520 to 565 nm, and the light-emitting color is inferred to be somewhat affected by the light emission corresponding to the small peaks around 630 to 670 nm.

(126) In the samples of Examples 39 to 58 in which Ho.sup.3+ was added as the rare earth metal ion, peaks were found around 550 nm and 650 nm.

(127) In these samples, the light-emitting color observed by the human visual sense was bright red-orange color, this is mainly due to the light emission corresponding to the peak around 650 nm, and this is inferred to be affected by the light emission corresponding to the peak around 550 nm.

(128) In the samples of Examples 59 to 74 in which two or more of Tm.sup.3+, Er.sup.3+ and Ho.sup.3+ were added in combination as the rare earth metal ions, according to the combinations, the peaks around 480 nm inferred to be due to Tm.sup.3+, the peaks around 550 nm inferred to be due to Er.sup.3+ and Ho.sup.3+, and the peaks around 650 nm inferred to be due to Ho.sup.3+ were found.

(129) In these samples, the light-emitting color observed by the human visual sense was white in the cases (Examples 59 to 62) of the combination of Tm.sup.3+ and Ho.sup.3+, blue to green in the cases (Examples 63 to 65) of the combination of Tm.sup.3+ and Er.sup.3+, yellow in the cases (Examples 66 to 68) of the combination of Er.sup.3+ and Ho.sup.3+, and various colors such as white, blue to green, and yellow in the cases (Examples 69 to 74) of the combinations of Tm.sup.3+, Er.sup.3+ and Ho.sup.3+, according to the mutual proportions of these three rare earth metal ions.

(130) These light-emitting colors are inferred to be caused by the combinations of the light emissions of a plurality of wavelengths, originating from the respective rare earth metal ions.

(131) (2) Discussion on Tm.sup.3+-Containing Up-Conversion Phosphor

(132) (2-1) Effect of the Content of Tm.sup.3+ on the Light-Emitting Properties

(133) FIGS. 3 and 4 show the measurement results (FIG. 3: the wavelength region from 450 to 510 nm; FIG. 4: the wavelength region from 750 to 850 nm) of the light emission spectra of the samples of Examples 1 to 7.

(134) From the results shown in FIGS. 3 and 4, it has been able to verify that the content ratio of Tm.sup.3+ affects the light-emitting properties, and it has also been able to verify that in order to obtain excellent light-emitting properties, the content of Tm.sup.3+ is preferably within a range from 0.05 to 1 at %, and in particular, within a range from 0.05 to 0.5 at %.

(135) (2-2) Effect of the Content of Yb.sup.3+ on the Light-Emitting Properties

(136) FIGS. 5 and 6 show the measurement results (FIG. 5: the wavelength region from 450 to 510 nm; FIG. 6: the wavelength region from 750 to 850 nm) of the light emission spectra of the samples of Examples 1 and 8 to 12, and Comparative Example 1.

(137) In the results shown in FIGS. 5 and 6, in the first place, from a comparison of Comparative Example 1 (not including Yb.sup.3+) with other Examples concerned, it has been able to verify that Yb.sup.3+ is an essential component to be included for the purpose of obtaining the targeted up-conversion light emission.

(138) From the results of Examples concerned, it has been able to verify that the content ratio of Yb.sup.3+ affects the light-emitting properties, and it has also been able to verify that for the purpose of obtaining excellent light-emitting properties, the content ratio of Yb.sup.3+ is preferably 20 at % or less, and in particular, within a range from 5 to 15 at %.

(139) (2-3) Effects of the Inclusion of the Monovalent Metal Ion on the Light-Emitting Properties

(140) FIGS. 7 and 8 show the measurement results (FIG. 7: the wavelength region from 450 to 510 nm; FIG. 8: the wavelength region from 750 to 850 nm) of the light emission spectra of the samples of Examples 1 and 13 to 15, and Comparative Example 2.

(141) In the results shown in FIGS. 7 and 8, in the first place, from a comparison of Comparative Example 2 (not including any monovalent metal ion) with other Examples concerned, it has been able to verify that the monovalent metal ion specified in the present invention is the essential component to be included.

(142) From the results of Examples concerned, it has been able to verify that for the purpose of obtaining excellent light-emitting properties, K.sup.+, Na.sup.+ and Li.sup.+ are preferable, K.sup.+ and Na.sup.+ are more preferable, and K.sup.+ is particularly preferable.

(143) (2-4) Effects of the Content of the Monovalent Metal Ion on the Light-Emitting Properties

(144) FIGS. 9 and 10 show the measurement results (FIG. 9: the wavelength region from 450 to 510 nm; FIG. 10: the wavelength region from 750 to 850 nm) of the light emission spectra of the samples of Examples 1 and 16 to 20, and Comparative Example 2.

(145) From the results shown in FIGS. 9 and 10, it has been able to verify that the content ratio of the monovalent metal ion affects the light-emitting properties, and it has also been able to be verified that for the purpose of obtaining excellent light-emitting properties, the content ratio of the monovalent metal ion is preferably 20 at % or less, and in particular, within a range from 5 to 15 at %.

(146) (3) Discussion on Er.sup.3+-Containing Up-Conversion Phosphor

(147) (3-1) Effects of the Content of Er.sup.3+ on the Light-Emitting Properties

(148) FIG. 11 shows the measurement results of the light emission spectra of the samples of Examples 21 to 26, and Comparative Example 3. FIG. 11 also includes an inserted graph plotting the light emission intensities, at 533 nm and 555 nm, of Examples concerned and Comparative Example concerned.

(149) In the results shown in FIG. 11, in the first place, from a comparison of Comparative Example 3 (not including any rare earth metal ion specified in the present invention) with other Examples concerned, it has been able to verify that the peaks of Examples are the peaks originating from Er.sup.3+.

(150) From the results of Examples concerned, it has been able to verify that the content ratio of Er.sup.3+ affects the light-emitting properties, and it has also been able to verify that for the purpose of obtaining excellent light-emitting properties, the content ratio of Er.sup.3+ is preferably within a range from 0.1 to 2 at %, and in particular, within a range from 0.2 to 0.6 at %.

(151) (3-2) Effects of the Content of Yb.sup.3+ on the Light-Emitting Properties

(152) FIG. 12 shows the measurement results of the light emission spectra of the samples of Examples 21 and 27 to 31, and Comparative Example 4. FIG. 12 also includes an inserted graph plotting the light emission intensities, at 522 nm, 533 nm, 547 nm and 554 nm, of Examples concerned and Comparative Example concerned.

(153) In the results shown in FIG. 12, in the first place, from a comparison of Comparative Example 4 (not including Yb.sup.3+) with other Examples concerned, it has been able to verify that Yb.sup.3+ is an essential component to be included for the purpose of obtaining the targeted up-conversion light emission.

(154) From the results of Examples concerned, it has been able to verify that the content ratio of Yb.sup.3+ affects the light-emitting properties, and it has also been able to verify that for the purpose of obtaining excellent light-emitting properties, the content ratio of Yb.sup.3+ is preferably within a range from 5 to 15 at %.

(155) (3-3) Effects of the Inclusion of the Monovalent Metal Ion on the Light-Emitting Properties

(156) FIG. 13 shows the measurement results of the light emission spectra of the samples of Examples 21 and 32 to 34, and Comparative Example 5. FIG. 13 also includes an inserted graph plotting the light emission intensities, at 522 nm, 533 nm, and 555 nm, of Examples concerned and Comparative Example concerned.

(157) In the results shown in FIG. 13, in the first place, from a comparison of Comparative Example 5 (not including any monovalent metal ion) with other Examples concerned, it has been able to verify that the monovalent metal ion specified in the present invention is an essential component to be included for the purpose of obtaining the targeted up-conversion light emission.

(158) From the results of Examples concerned, it has been able to verify that for the purpose of obtaining excellent light-emitting properties, K.sup.+, Na.sup.+ and Rb.sup.+ are preferable, K.sup.+ and Na.sup.+ are more preferable, and K.sup.+ is particularly preferable.

(159) (3-4) Effects of the Content of the Monovalent Metal Ion on the Light-Emitting Properties

(160) FIG. 14 shows the measurement results of the light emission spectra of the samples of Examples 21 and 35 to 38, and Comparative Example 5. FIG. 14 also includes an inserted graph plotting the light emission intensities, at 533 nm and 555 nm, of Examples concerned and Comparative Example concerned.

(161) From the results shown in FIG. 14, it has been able to verify that the content ratio of the monovalent metal ion affects the light-emitting properties, and it has also been able to verify that for the purpose of obtaining excellent light-emitting properties, the content ratio of the monovalent metal ion is preferably within a range from 5 to 15 at %.

(162) (4) Discussion on Ho.sup.3+-Containing Up-Conversion Phosphor

(163) (4-1) Effects of the Content of Ho.sup.3+ on the Light-Emitting Properties

(164) FIG. 15 shows the measurement results of the light emission spectra of the samples of Examples 39 to 46.

(165) From the results shown in FIG. 15, it has been able to verify that the content ratio of Ho.sup.3+ affects the light-emitting properties, and it has also been able to verify that for the purpose of obtaining excellent light-emitting properties, the content ratio of Ho.sup.3+ is preferably 2 at % or less, and in particular, within a range from 0.03 to 1 at %.

(166) (4-2) Effects of the Content of Yb.sup.3+ on the Light-Emitting Properties

(167) FIG. 16 shows the measurement results of the light emission spectra of the samples of Examples 41 and 47 to 51, and Comparative Example 6.

(168) In the results shown in FIG. 16, in the first place, from a comparison of Comparative Example 6 (not including Yb.sup.3+) with other Examples concerned, it has been able to verify that Yb.sup.3+ is an essential component to be included for the purpose of obtaining the targeted up-conversion light emission.

(169) From the results of Examples concerned, it has been able to verify that the content ratio of Yb.sup.3+ affects the light-emitting properties, and it has also been able to verify that for the purpose of obtaining excellent light-emitting properties, the content ratio of Yb.sup.3+ is preferably 20 at % or less, and in particular, within a range from 5 to 15 at %.

(170) (4-3) Effects of the Inclusion of the Monovalent Metal Ion on the Light-Emitting Properties

(171) FIG. 17 shows the measurement results of the light emission spectra of the samples of Examples 41 and 52 to 54, and Comparative Example 7.

(172) In the results shown in FIG. 17, in the first place, from a comparison of Comparative Example 7 (not including any monovalent metal ion) with other Examples concerned, it has been able to verify that the monovalent metal ion specified in the present invention is an essential component to be included for the purpose of obtaining the targeted up-conversion light emission.

(173) From the results of Examples concerned, it has been able to verify that for the purpose of obtaining excellent light-emitting properties, K.sup.+, Na.sup.+ and Rb.sup.+ are preferable, and K.sup.+ and Na.sup.+ are more preferable.

(174) (4-4) Effects of the Content of the Monovalent Metal Ion on the Light-Emitting Properties

(175) FIG. 18 shows the measurement results of the light emission spectra of the samples of Examples 41 and 55 to 58, and Comparative Example 7.

(176) From the results shown in FIG. 18, it has been able to verify that the content ratio of the monovalent metal ion affects the light-emitting properties, and it has also been able to verify that for the purpose of obtaining excellent light-emitting properties, the content ratio of the monovalent metal ion is preferably within a range from 5 to 15 at %.

(177) (5) Discussion on Up-Conversion Phosphor Allowed to Contain Combination of Two or More Rare Earth Metal Ions Specified in the Present Invention

(178) FIG. 19 shows the measurement results of the light emission spectra of the samples (using Tm.sup.3+ and Ho.sup.3+, in combination) of Examples 59 to 62; FIG. 20 shows the measurement results of the light emission spectra of the samples (using Tm.sup.3+ and Er.sup.3+, in combination) of Examples 63 to 65; FIG. 21 shows the measurement results of the light emission spectra of the samples (using Er.sup.3+ and Ho.sup.3+, in combination) of Examples 66 to 68; and FIG. 22 shows the measurement results of the light emission spectra of the samples (using Tm.sup.3+, Er.sup.3+ and Ho.sup.3+, in combination) of Examples 69 to 74.

(179) From the results shown in FIGS. 19 to 22, it has been able to verify that when two or more of the rare earth metal ions specified in the present invention are combined, according to the content proportions of the rare earth metal ions, the peak intensities are allowed to vary and the light-emitting color is allowed to be controlled.

(180) (6) Others: Effects of Burning Temperature on Light-Emitting Properties

(181) FIGS. 23 to 25 show the measurement results of the light emission spectra of the samples of Examples 1 and 75 to 79.

(182) From the results shown in FIGS. 23 to 25, it has been able to verify that the burning temperature affects the light-emitting properties to a certain degree, and it has also been able to verify that for the purpose of obtaining excellent light-emitting properties, the burning temperature is preferably within a range from 550 to 800° C., and in particular, within a range from 550 to 700° C.

INDUSTRIAL APPLICABILITY

(183) The up-conversion phosphor of the present invention can be applied to the same applications as the applications of conventional phosphors, such as color displays, infrared sensors, optical recording data and laser materials. In particular, the up-conversion phosphor concerned allows the use of low-energy excitation light sources, and hence is suitable as a phosphor to substitute for conventional down-conversion phosphors and to be excellent in energy saving and stability.