Phosphor and Fluorescent Lamp Using the Same

The present invention relates to a blue-color light-emitting aluminate phosphor and a fluorescent lamp using the same.

Recently, demand has arisen for general illumination fluorescent lamps having high output and high color-rendering properties. This demand is met by three-band type fluorescent lamps wherein blue, green, and red phosphors, having emission spectrum distributions of relatively narrow wavelength ranges, are mixed in an appropriate mixing ratio.

A recent three-band type fluorescent lamp uses an aluminate phosphor as a blue-color light-emitting component. However, a europium-activated aluminate phosphor [(Ba,Eu)Mg.sub.2 Al.sub.16 O.sub.27 ] (Japanese Patent Publication (Kokoku) No. 52-22836) as a known blue phosphor is not satisfactory, since its emission intensity descreases during use. Other europium-activated aluminate phosphors [(Ba,Eu)O.eAl.sub.2 O.sub.3.fy.sub.2 O.sub.3 ] (Japanese Patent Disclosure (Kokai) No. 60-139784) and [Ba.sub.1-g-h Sr.sub.g Mg.sub.i.Al.sub.j O.sub.1+i+j/2 :Eu.sub.h.sup.2+ ] (Japanese Patent Disclosure (Kokai) No. 56-86982) are also not satisfactory since their emission intensities are low and decrease during use.

The emission colors of the respective phosphors of these types of fluorescent lamp differ greatly. When the emission outputs (emission inensities) of the respective phosphors decrease while the lamp is in use, color deviation occurs, degrading the color rendering properties.

Japanese Patent Disclosure (Kokai) No. 57-207678 discloses a fluorescent lamp having a combination of 3(M,Eu).sub.3 (PO.sub.4).sub.2.m'Cl.sub.2 or k(M.sub.1-o Eu.sub.o O).lP.sub.2 O.sub.5 mM'X.sub.2.nB.sub.2 O.sub.8 as a blue phosphor, (Re.sub.1-p-q-r Tb.sub.p Ce.sub.q As.sub.r).sub.2 O.sub.3 .mu.SiO.sub.2..nu.P.sub.2 O.sub.5 as a green phosphor, and (Y,Eu).sub.2 O.sub.3 as a red phosphor. With this lamp, however, color deviation occurs during use, due to a difference in the degradation rates of the respective phosphors, thus a decrease in the total luminous flux intensity of the lamp is large.

The present invention has been developed to solve the above problems, and has as its object to provide a blue-color light-emitting aluminate phosphor which has a high emission output and a low decrease in its emission intensity during use, and a fluorescent lamp using the same.

The phosphor of the present invention is a blue-color light-emitting aluminate phosphor represented by a general formula (Ba.sub.w Ca.sub.x Mg.sub.y Eu.sub.z)O.al.sub.2 O.sub.3.bSiO.sub.2 where 0.1.ltoreq.w.ltoreq.0.5, 0.0004.ltoreq.x.ltoreq.0.0020, 0.1.ltoreq.y.ltoreq.0.8, 0.03.ltoreq.z.ltoreq.0.10, w+x+y+z+1, 1.5.ltoreq.a.ltoreq.4.5, and 0.0005<b.ltoreq.0.0030.

It is preferable that a satisfies 2.0.ltoreq.a.ltoreq.3.0 and that x satisfies 0.0006.ltoreq.x.ltoreq.0.0015.

Eu can be partially substituted by Mn. The substitution ratio of Mn is twice or less than Eu in molar ratio. In this case, coefficient z depends on the total amount of Eu and Mn.

The phosphor (Ba.sub.w Ca.sub.x Mg.sub.y Eu.sub.z)O.aAl.sub.2 O.sub.3.bSiO.sub.2 of the present invention can be synthesized as follows:

In selecting phosphor materials, at least one member selected from the barium compound group consisting of barium oxide, barium hydroxide, barium carbonate, and so on can be used as a barium source; at least one member selected from the calcium compound group consisting of calcium oxide, calcium hydroxide, calcium carbonate and so on can be used as a calcium source; at least one member selected from the magnesium compound group consisting of magnesium oxide, magnesium hydroxide, magnesium carbonate, and so on can be used as a magnesium source; at least one member selected from the europium compound group consisting of europium oxide, europium fluoride, and so on can be used as a europium source; at least one member selected from an aluminum compound group consisting of aluminum oxide, aluminum hydroxide, and so on can be used as an aluminum source; and at least one member selected from the silicon compound group consisting of silicon dioxide and so on can be used as a silicon source.

Predetermined amounts of the above materials are weighed and mixed thoroughly. The mixture is put in a refractory container and sintered in air at 1,200.degree. to 1,600.degree. C. for 3 to 4 hours. The obtained sintered product is pulverized and treated by washing with water and so on.

The powder obtained by pulverization is dried and put in the refractory container once again, and sintered in a reducing atmosphere at 1,400.degree. to 1,600.degree. C. for 3 to 4 hours. When the sintered product is pulverized and treated by washing with water and so on, a blue-color light-emitting aluminate phosphor of the present invention can be obtained.

FIG. 1 shows a spectrum distribution of the blue-color light-emitting aluminate phosphor of the present invention. It can be seen from FIG. 1 that the phosphor of the present invention has an emission spectrum of a narrow wavelength range in the vicinity of 450 nm.

The fluorescent lamp according to the present invention is obtained by coating, on the inner surface of a glass bulb, a mixture of the blue phosphor (first phosphor); a second phosphor having an emission spectrum in a visible green color range and represented by a general formula Ln.sub.2 O.sub.3.c(Mg.sub.1-u Ca.sub.u)O.d[(Al.sub.2 O.sub.3).sub.1-v.(SiO.sub.2).sub.v ] (where Ln is at least one element selected from the group consisting of lanthanum, gadolinium, yttrium, cerium, and terbium, and 1.5.ltoreq.c.ltoreq.5.0, 2.5.ltoreq.d.ltoreq.14.0, 0.001.ltoreq.u.ltoreq.0.005, and 0.0002.ltoreq.v.ltoreq.0.0010); and a third phosphor having an emission spectrum in a visible red color range and represented by a general formula (Y.sub.1-t Eu.sub.t).sub.2 O.sub.3 (where 0.020.ltoreq.t.ltoreq.0.065). The first, second, and third phosphors are contained at ratios of 0.2 to 35% by weight, 35 to 60% by weight, and 30 to 60% by weight, respectively, with respect to 100% by weight of the mixture.

If the mixing ratios of the first, second, and third phosphors of the present invention fall outside the above ranges, the color rendering properties are decreased.

The second phosphor is disclosed in Japanese Patent Application No. 61-120208 by the present inventors.

FIG. 1 shows the emission spectrum of the blue-color phosphor according to the present invention.

The above materials were mixed thoroughly. The obtained mixture was sintered in air at 1.350.degree. C. for 4 hours. The sintered product was pulverized and washed with water. The powder obtained by pulverization was dried and sintered in a reducing atmosphere at 1,400.degree. C. for 4 hours. Finally, the sintered powder was pulverized, washed with water, and dried again to obtain a phosphor.

The composition of the obtained phosphor was (Ba.sub.0.449 Ca.sub.0.001 Mg.sub.0.5 Eu.sub.0.05)O.2.5Al.sub.2 O.sub.3.0.001SiO.sub.2. The emission intensities of this phosphor, under excitation by the mercury bright line of 254 nm, were 110% and 120% those of conventional blue-color light-emitting aluminum phosphors (Ba,Eu)Mg.sub.2 Al.sub.16 O.sub.27 and (Ba,Eu)O.eAl.sub.2 O.sub.3.fY.sub.2 O.sub.3, respectively. Its emission intensity after the lamp had been ON for 1,000 hours was 180% that of (Ba,Eu)O.eAl.sub.2 O.sub.3.fY.sub.2 O.sub.3.

The above materials were treated following the same procedures as in Example 1. The composition of the obtained phosphor was (Ba.sub.0.198 Ca.sub.0.002 Mg.sub.0.7 Eu.sub.0.1)O.3.5Al.sub.2 O.sub.3.0.002SiO.sub.2. The emission intensities of this phosphor, under excitation by the mercury bright line of 254 nm, was 114% that of (Ba,Eu)O.eAl.sub.2 O.sub.3.fY.sub.2 O.sub.3, and was 135% that thereof after the lamp had been ON for 1,000 hours.

The above materials were treated following the same procedures as in Example 1. The composition of the obtained phosphor was (Ba.sub.0.2 Ca.sub.0.0015 Mg.sub.0.7385 Eu.sub.0.06)O.2.0Al.sub.2 O.sub.3 0.003SiO.sub.2. The emission intensity of this phosphor, under excitation by the mercury bright line of 254 nm, was 118% that of (Ba,Eu)O.eAl.sub.2 O.sub.3.fY.sub.2 O.sub.3, and was 155% that thereof after the lamp had been ON for 1,000 hours.

Table 1 compares the emission intensities of the phosphors (Examples 1 to 3, Examples 4 to 16, in accordance with the same manufacturing method as in Examples 1 to 3) and conventional blue-color light-emitting aluminum phosphors (Controls 1 and 2), and their respective degradations. It can be seen from Table 1 that a phosphor of the present invention, represented by a general formula (Ba.sub.w Ca.sub.x Mg.sub.y Eu.sub.z)O.aAl.sub.2 O.sub.3.bSiO.sub.2, has higher emission intensities immediately after excitation and after the lamp has been ON for 1,000 hours. It can also be seen that these high emission intensities can be obtained when 2.0<a-3.0 or 0.0006<x<0.0015.

Fifteen percent by weight of (Ba.sub.0.3 Ca.sub.0.002 Mg.sub.0.6 Eu.sub.0.098)O.2.5Al.sub.2 O.sub.3.0.0030SiO.sub.2 as a blue phosphor, 50% by weight of (La.sub.0.5 Ce.sub.0.3 Tb.sub.0.2).sub.2 O.sub.3.2.0.(Mg.sub.0.999 Ca.sub.0.001)O.8.0[(Al.sub.2 O.sub.3).sub.0.9996 (SiO.sub.2).sub.0.0004 [ as a green phosphor, and 35% by weight of (Y.sub.0.96 Eu.sub.0.04).sub.2 O.sub.3 as a red phosphor were mixed together. The mixture was coated on the inner surface of a glass bulb to prepare a fluorescent lamp FL22SS/18 of the present invention.

The color of the light emitted by this fluorescent lamp, after it had been ON for 0 hours (immediately after manufacture) was x=0.340 and Y=0.357 on the x, y chromaticity coordinate diagram. After this fluorescent lamp was ON for 500 hours, the color of its light was measured to be x=0.340 and y=0.359. In contrast to this, the color of the light emitted by a lamp according to Control 3 was x=0.340 and y=0.354, after the lamp had been ON for 0 hours, and was x=0.360 and y=0.365, after the lamp had been ON for 500 hours.

The total luminous fluxes (emission outputs) after the lamp had been ON for 500 hours were 102% and 112% those of Control 3, respectively.

As a result, it is apparent that the lamp of Example 17 has less color deviation and a smaller decrease in its emission output than the lamp according to Control 3.

Similar tests were performed by changing the formula and mixing ratio of the respective color phosphors (Examples 18 to 31).

Table 2 shows the results in this case. The fluorescent lamps of the present invention are superior to that of Control 3, in that their color deviation and decrease in emission output are less. Total Emitted Color Emitted Color Total Luminous Blue Phosphor G reen Phosphor Red Phosphor After 0 hrs. After 500 hrs. Luminous Flux After Mixing Ratio Mixing Ratio Mixing Ratio (x, y color (x, y color F lux After 500 hrs. No. Composition (% by weight) Composition (% by weight) Composition (% by weight) Representation) Representation) 0 hrs. (%) (%) Example 17 (Ba.sub.0.3 Ca.sub.0.0020 Mg.sub.0.6 15 (La.sub.0.5 Ce.sub.0.3 Tb.sub.0.2).sub.2 50 (Y.sub.0.960 35 x = 0.338 x = 0.340 102 112 Eu.sub.0.0980)O.2.5Al.sub.2 O.sub.3. O.sub.3.2.0(Mg.sub.0.999 Ca.sub.0.001) Eu.sub.0.040).sub.2 y = 0.357 y = 0.359 0.0030SiO.sub.2 O.8.0[(Al.sub.2 O.sub.3).sub.0.9996 O.sub.3 (SiO.sub.2).sub.0.0004 ] 18 (Ba.sub.0.449 Ca.sub.0.0010 Mg.sub.0.5 10 (La.sub.0.5 Ce.sub.0.3 Tb.sub.0.2).sub.2 60 (Y.sub.0.945 30 x = 0.340 x = 0.341 101 110 Eu.sub.0.05)O.2.5Al.sub.2 O.sub.3. O.sub.3.2.5(Mg.sub.0.998 Ca.sub.0.002) Eu.sub.0.055).sub.2 y = 0.356 y = 0.358 0.0010SiO.sub.2 O.5.0[(Al.sub.2 O.sub.3).sub.0.9998 O.sub.3 (SiO.sub.2).sub.0.0002 ] 19 (Ba.sub.0.198 Ca.sub.0.0020 Mg.sub.0.7 5 (Gd.sub.0.6 Ce.sub.0.3 Tb.sub.0.1).sub.2 55 (Y.sub.0.965 40 x = 0.341 x = 0.343 103 109 Eu.sub.0.10)O.3.5Al.sub.2 O.sub.3. O.sub.3.3.0(Mg.sub.0.999 Ca.sub.0.001) Eu.sub.0.035).sub.2 y = 0.353 y = 0.354 0.0020SiO.sub.2 0.10[(Al.sub.2 O.sub.3).sub.0.9990 O.sub.3 (SiO.sub.2).sub.0.0010 ] 20 (Ba.sub.0.2 Ca.sub.0.0015 Mg.sub.0.3385 20 (Y.sub.0.7 Ce.sub.0.15 Tb.sub.0.15).sub.2 35 (Y.sub.0.980 45 x = 0.340 x = 0.342 100 111 Eu.sub.0.06 )O.2.0AlO.sub.3. O.sub.3.2.0(Mg.sub.0.995 Ca.sub.0.005) Eu.sub.0.020).sub.2 y = 0.355 y = 0.356 0.0030SiO.sub.2 O.2.5[(Al.sub.2 O.sub.3).sub.0.9998 O.sub.3 (SiO.sub.2).sub.0.0002 ] 21 (Ba.sub.0.3188 Ca.sub.0.0012 15 (Ce.sub.0.65 Tb.sub.0.35).sub.2 O.sub.3. 40 (Y.sub.0.935 45 x = 0.339 x = 0.340 102 112 Mg.sub.0.60 Eu.sub.0.08)O. 1.5(Mg.sub.0.999 Ca.sub.0.001)O. Eu.sub.0.065).sub.2 y = 0.352 y = 0.355 4.5Al.sub.2 O.sub.3.0.0022 4.0[(Al.sub.2 O.sub.3).sub.0.9998 O.sub.3 SiO.sub.2 (SiO.sub.2).sub.0.0002 ] 22 (Ba.sub.0.3 Ca.sub.0.0017 Mg.sub.0.6283 10 (La.sub.0.7 Tb.sub.0.3).sub.2 O.sub.3. 45 (Y.sub.0.975 45 x = 0.342 x = 0.345 101 110 Eu.sub.0.07)O.3.0Al.sub.2 O.sub.3. 5.0(Mg.sub.0.996 Ca.sub.0.004) Eu.sub.0.025).sub.2 y = 0.350 y = 0.353 0.0005SiO.sub.2 O.8.0[(Al.sub.2 O.sub.3).sub.0.9997 O.sub.3 (SiO.sub.2).sub.0.0003 ] 23 (Ba.sub.0.1492 Ca.sub.0.0008 Mg.sub.0.8 O 10 (Gd.sub.0.8 Tb.sub.0.2).sub.2 60 (Y.sub.0.950 30 x = 0.341 x = 0.344 103 109 Eu.sub.0.05)O.1.8Al.sub.2 O.sub.3. O.sub.3.3.5(Mg.sub.0.998 Ca.sub.0.002) Eu.sub.0.050).sub.2 y = 0.358 y = 0.360 0.0017SiO.sub.2 O.12[Al.sub.2 O.sub.3).sub.0.9998 O.sub.3 (SiO.sub.2).sub.0.0002 ] 24 (Ba.sub.0.2494 Ca.sub.0.0006 Mg.sub.0.65 25 (La.sub.0.6 Ce.sub.0.2 Tb.sub.0.2).sub.2 45 (Y.sub.0.970 30 x = 0.340 x = 0.342 101 111 Eu.sub.0.10)O.2.3Al.sub.2 O.sub.3. O.sub.3 .4.0(Mg.sub.0.999 Ca.sub.0.001) Eu.sub.0.030).sub.2 y = 0.354 y = 0.357 0.0025SiO.sub.2 O.11.5 [(Al.sub.2 O.sub.3).sub.0.9993 O.sub.3 (SiO.sub.2).sub.0.0007 ] 25 (Ba.sub.0.5495 Ca.sub.0.0005 Mg.sub.0.40 0.4 (Gd.sub.0.6 Ce.sub.0.3 Tb.sub.0.1).sub.2 39.8 (Y.sub.0.970 59.8 x = 0.483 x = 0.484 109 110 Eu.sub.0.05)O.3.2AlO.sub.3. O.sub.3 .2.0(Mg.sub.0.995 Ca.sub.0.005) Eu.sub.0.030).sub.2 y = 0.464 y = 0.467 0.0008SiO.sub.2 O.5.0[(Al.sub.2 O.sub.3).sub.0.9996 O.sub.3 (SiO.sub.2).sub.0.0004 ] 26 (Ba.sub.0.2 Ca.sub.0.0013 0.3 (Y.sub.0.6 Ce.sub.0.3 Tb.sub.0.1).sub.2 O.sub.3. 40.9 (Y.sub.0.975 58.8 x = 0.482 x = 0.485 110 112 Mg.sub.0.7087 Eu.sub.0.09)O. 1.5(Mg.sub.0.998 Ca.sub.0.002)O. Eu.sub.0.025).sub.2 y = 0.465 y = 0.468 2.9Al.sub.2 O.sub.3 .0.0027 13[(Al.sub.2 O.sub.3).sub.0.9992 O.sub.3 SiO.sub.2 (SiO.sub.2).sub.0.0008 ] 27 (Ba.sub.0.5 Ca.sub.0.0017 Mg.sub.0.4903 0.2 (Ce.sub.0.75 Tb.sub.0.25).sub.2 O.sub.3. 39.9 (Y.sub.0.980 59.9 x = 0.484 x = 0.487 111 110 Eu.sub.0.08)O.1.6Al.sub.2 O.sub.3. 2.5 Mg.sub.0.996 Ca.sub.0.004) Eu.sub.0.020).sub.2 y = 0.464 y = 0.466 0.0016SiO.sub.2 O.6.0[(Al.sub.2 O.sub.3).sub.0.9998 O.sub.3 (SiO.sub.2).sub.0.0002 ] 28 (Ba.sub.0.3982 Ca.sub.0.0018 Mg.sub.0.5 O 0.5 (La.sub.0.6 Tb.sub.0.4).sub.2 40.0 (Y.sub.0.950 59.5 x = 0.483 x = 0.484 112 111 Eu.sub.0.10)O.4.0Al.sub.2 O.sub.3. O.sub.3 .2.0Mg.sub.0.999 Ca.sub.0.001) Eu.sub.0.050).sub.2 y = 0.463 y = 0.466 0.0030SiO.sub.2 O.2.5[(Al.sub.2 O.sub.3).sub.0.9995 O.sub.3 (SiO.sub.2).sub.0.0005 ] 29 (Ba.sub.0.2585 Ca.sub.0.0015 Mg.sub.0.70 0.3 (Gd.sub.0.7 Tb.sub.0.3).sub.2 41.1 (Y.sub.0.965 58.6 x = 0.483 x = 0.485 110 108 Eu.sub.0.04)O.3.4Al.sub.2 O.sub.3. O.sub.3.3.0(Mg.sub.0.995 Ca.sub.0.005) Eu.sub.0.035).sub.2 y = 0.463 y = 0.467 0.0010SiO.sub.2 O.5.5[(Al.sub.2 O.sub.3).sub.0.9996 O.sub.3 (SiO.sub.2).sub.0.0004 ] 30 (Ba.sub.0.1195 Ca.sub.0.0005 Mg.sub.0.80 0.4 (La.sub.0.6 Gd.sub.0.1 Gd.sub.0.2 Tb.sub.0.1).sub.2 40.8 (Y.sub.0.950 58.8 x = 0.482 x = 0.485 109 108 Eu.sub.0.08)O.2.8AlO.sub.3. O.sub.3 .4.5(Mg.sub.0.997 Ca.sub.0.003) Eu.sub.0.050).sub.2 y = 0.465 y = 0.469 0.0009SiO.sub.2 O.7.0[(Al.sub.2 O.sub.3).sub.0.9997 O.sub.3 (SiO.sub.2).sub.0.0003 31 (Ba.sub.0.4588 Ca.sub.0.0012 0.3 (La.sub.0.5 Gd.sub.0.1 Ce.sub.0.2 39.9 (Y.sub.0.945 59.8 x = 0.482 x = 0.484 110 110 Mg.sub.0.45 Eu.sub.0.09)O. Tb.sub.0.2).sub.2 O.sub.3.5.0(Mg.sub.0.999 Eu.sub.0.055).sub.2 y = 0.462 y = 0.465 4.4Al.sub.2 O.sub.3 .0.0013 Ca.sub.0.001)O.14[(Al.sub.2 O.sub.3).sub.0.9991 O.sub.3 SiO.sub.2 (SiO.sub.2).sub.0.0009 ] Control 3 3(Sr.sub.0.98 Eu.sub.0.02 O). 19 (La.sub.0.1 Tb.sub.0.2 Ce.sub.0.697 44 (Y.sub.0.950 37 x = 0.340 x = 0.360 100 100 0.92 P.sub.2 O.sub.5 .0.33 Li.sub.0.003 ).sub.2 O.sub.3. Eu.sub.0.050).sub.2 y = 0.354 y = 0.365 CaCl.sub.2 .0.08 B.sub.2 O.sub.3 0.9P.sub.2 O.sub.5 .0.2SiO.sub.2 O.sub.3

Table 3 shows the emission outputs (total luminous fluxes) of fluorescent lamps, obtained by coating the blue, green, and red phosphors of Example 17 on the inner surfaces of different glass bulbs, immediately after manufacture (after the lamps had been ON for 0 hours) and after the lamps had been ON for 500 hours. The rates of degradation in emission output of the respective phosphors of Example 17 are smaller than those of the respective phosphors used in the conventional fluorescent lamp (Control 4), and the rates of degradation in emission output of the respective colors are similar. This illustrates clearly that a decrease in total luminous flux and color deviation of a three-wavelength range fluorescent lamp are small, after the lamp has been is use.

Table 4 shows the results obtained when the respective phosphors of Table 3 were removed from the corresponding fluorescent lamps and the reflectances of the lamps were measured. The phosphors of Example 17 have higher reflectances than those of Control 4. This is attributable to the following fact.

In a conventional fluorescent lamp, a reaction occurs therein between a conventional phosphor and mercury for excitation during use of the lamp. This degrades the phosphor, resulting in a lower reflectance. Since the reflectance degrades in a similar manner as the emission output does, it is assumed that a degradation in reflectance causes a degradation in emission output.