A phosphorescent phosphor comprising a matrix expressed by M.sub.1-x Al.sub.2 O.sub.4-x (except X=0) in which M is at least one metal element selected from a group consisting of calcium, strontium and barium. X is in a range -0.33.ltoreq..times..ltoreq.0.60 (except x=0). Europium is doped to said matrix as an activator and at least one element selected from a group consisting of lanthanum, cerium, praseodymium, neodymium, samarium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium is doped to said matrix as a co-activator. Magnesium is doped to M.

BACKGROUND OF THE INVENTION 
The present invention relates to a phosphorescent phosphor, and more 
particularly, to a novel phosphorescent phosphor which shows excellent 
photo-resistance required for the phosphorescent phosphor to be utilized 
both indoors and outdoors mainly as a night-time display, and which shows 
an extremely long afterglow characteristics. 
Generally, the afterglow time of a fluorescent substance is short, i.e., 
the light emitted from the fluorescent substance decays immediately after 
removal from the source of excitation. Unlike such a fluorescent 
substance, some substances emit light after having absorbed ultraviolet 
radiation or the like and afterglow thereof that can be visually observed 
continues for a considerable time (ranging from several tens of minutes to 
several hours) after the source of stimulus is cut off. Such substances 
are called phosphorescent phosphors. 
As phosphors, sulfide phosphors are known. Examples of sulfide phosphors 
include CaS: Bi (which emits light of violet blue), CaSrS: Bi (which emits 
light of blue), ZnS: Cu (which emits light of green) and ZnCdS: Cu (which 
emits light of yellow or orange). However, any of these sulfide phosphors 
is chemically unstable and shows degraded light resistance, i.e., it 
suffers from problems that must be solved for practical use. 
The most extensively used phosphorescent phosphor among such sulfide 
phosphors is zinc sulfide phosphor (ZnS: Cu). However, zinc sulfide 
phosphor is decomposed as the result of irradiation by ultraviolet 
radiation in the presence of moisture and thus blackens or reduces the 
luminance thereof. Therefore, it is difficult to use this phosphor in 
fields where it is placed outdoors and exposed to a direct sunlight, that 
is, application thereof is limited to luminous clocks/watches or 
clocks/watches and instrument dials, evacuation guiding signs or indoor 
nighttime display. 
Even when zinc sulfide phosphor is used for a luminous clock, since the 
afterglow thereof which allows the time to be visually recognized lasts 
only from 30 minutes to 2 hours, a radioactive substance must be doped to 
the phosphorescent phosphor and a self-luminous paint which keeps emitting 
light by absorbing an energy of radiation from radioactive substance must 
be employed. 
In view of the foregoing, the inventor of the present invention has 
disclosed a phosphorescent phosphor in Japanese Patent Application No. 
6-4989 which shows afterglow characteristics that last much longer than 
those of presently available sulfide phosphorescent phosphors, and which 
is chemically stable and shows excellent photo-resistance over a long time 
and which comprises a matrix expressed by MAl.sub.2 O.sub.4 in which M is 
at least one metal element selected from a group consisting of calcium, 
strontium and barium. 
According to the foregoing invention, the inventor of the present invention 
took note of alkaline earth metal type aluminate activated by europium or 
the like, which is a novel phosphorescent phosphor completely different 
from conventional sulfide phosphors, conducted various experiments, and 
discovered that this phosphorescent phosphor showed afterglow 
characteristics which lasted much longer than those of currently available 
sulfide phosphors and was chemically stable because of it is an oxide type 
substance and showed excellent photo-resistance. Therefore, the inventors 
came to the conclusion that this phosphorescent phosphors could solve all 
the problems of the prior art and could thus be employed in various 
applications as a luminous paint or pigment which could be visually 
recognized for a night without containing radioactivity. 
As the foregoing phosphorescent phosphor, there has been suggested a 
phosphorescent phosphor comprising a matrix expressed by MAl.sub.2 O.sub.4 
in which M is at least one metal element selected from a group consisting 
of calcium, strontium and barium, wherein europium is doped to said matrix 
as an activator and at least one element selected from a group consisting 
of lanthanum, cerium, praseodymium, neodymium, samarium, gadolinium, 
terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium is 
doped to said matrix as a co-activator. 
Also a phosphorescent phosphor has been suggested which comprised a matrix 
including a plurality of metal elements consisting of magnesium doped to 
M. 
In addition to the two types of phosphorescent phosphors, another 
phosphorescent phosphor has been suggested, in which 0.002% to 20% of 
europium is doped to said matrix as an activator in terms of mol % 
relative to the metal element expressed by M. Another phosphorescent 
phosphor has been suggested, 0.002% to 20% of at least one element 
selected from a group consisting of lanthanum, cerium, praseodymium, 
neodymium, samarium, gadolinium, terbium, dysprosium, holmium, erbium, 
thulium, ytterbium and lutetium is doped to said matrix as a co-activator 
in terms of mol % relative to the metal element expressed by M in addition 
to the europium serving as the activator. 
Additionally, it is possible to add 1-10% by weight of boric acid as flux 
to the starting material to perform the aforementioned syntheses of the 
phosphorescent phosphors. In this case, if the amount of flux is less than 
1% by weight, the effect of flux vanishes and if the amount of flux 
exceeds 10% by weight, flux is solidified, so that it becomes difficult to 
perform the milling and sieving which must be performed later. 
Since the foregoing novel phosphorescent phosphors have not been laid open, 
the contents of the invention applied in Japanese Patent Application No. 
6-4989 will now be described. 
Examples of phosphorescent phosphor according to the invention disclosed in 
Japanese Patent Application No. 6-4989 (hereinafter called as a "applied 
invention") and expressed by MAl.sub.2 O.sub.4 will now be described, the 
examples differing from each other in terms of the type (M) of a metal 
element, concentration of europium which is the activator or type and 
concentration of the co-activator. 
First, a phosphorescent phosphor which employs strontium as the metal 
element (M), which employs europium as an activator and which employs no 
co-activator will be described as example 1 of the applied invention. 
Example 1 of Applied Invention: Synthesis of SrAl.sub.2 O.sub.4 : Eu 
phosphorescent phosphor and characteristics thereof Sample 1-(1) 
As an activator 1.76 g (0.005 mol) of europium oxide (Eu.sub.2 O.sub.3) was 
added to 146.1 g (0.99 mol) of strontium carbonate having reagent grade 
and 102 g (1 mol) of alumina having reagent grade and, further, 5 g (0.08 
mol) of boric acid was added as flux thereto. After the resultant mixture 
was sufficiently mixed using a ball mill, the sample was fired for 1 hour 
at 1300.degree. C. in a stream of nitrogen-hydrogen mixture gas (97:3) 
(flow rate: 0.1 liter/min) using an electric furnace. Thereafter, the 
sample was cooled to a room temperature for about 1 hour. The obtained 
powder compound was sieved having 100 mesh to obtain phosphorescent 
phosphor sample 1-(1). 
FIG. 1 shows the results of analysis of the crystal structure of the 
obtained phosphorescent phosphor by XRD (X-ray diffractiometry). It was 
discovered from the diffraction peak characteristics that the obtained 
phosphorescent phosphor was SrAl.sub.2 O.sub.4 having spinel structure. 
FIGS. 2A and 2B respectively show the excitation spectrum of that 
phosphorescent phosphor and the afterglow emission spectrum thereof 
obtained after removal from the source of light. 
From the same figure, it was made evident that the peak wavelength of the 
emission spectrum of SrAl.sub.2 O.sub.4 : Eu phosphorescent phosphor is 
about 520 nm which indicates green. 
FIG. 3 and Table 2 show the results of the comparison between the 
measurements of the afterglow characteristics of the obtained SrAl.sub.2 
O.sub.4 : Eu phosphorescent phosphor and those of ZnS: Cu phosphor which 
is available on the market and which emits light of green (manufactured by 
Nemoto & Co., LTD: trade mark: GSS, and the wavelength of emission peak: 
530 nm). 
The afterglow characteristics were measured in the manner described below: 
0.05 g of the obtained phosphorescent phosphor powder was taken on a 
sample plate having an inner diameter of 8 mm and made of aluminum (sample 
thickness: 0.1 g/cm.sub.2), and that sample was left in the darkness for 
about 15 hours to remove afterglow. Thereafter, the sample was irradiated 
by a D.sub.65 standard light source at 200 lux for 10 minutes, and the 
obtained afterglow was measured using a luminance measuring device which 
employed a photo-multiplier. 
As can be apparent from FIG. 3, the afterglow of SrAl.sub.2 O.sub.4 : Eu 
phosphorescent phosphor according to the present invention is highly 
bright and the decay thereof is slow. As the time passes, a difference in 
the intensity of afterglow between SrAl.sub.2 O.sub.4 : Eu phosphorescent 
phosphor and ZnS: Cu phosphor increases. In FIG. 3, the broken line 
indicates the level of visually recognizable light intensity 
(corresponding to a luminance of about 0.3 mCd/m.sup.2). It can be 
inferred from this broken line which indicates the afterglow 
characteristic of SrAl.sub.2 O.sub.4 : Eu phosphorescent phosphor that 
afterglow thereof will be recognized 24 hours later. When afterglow of 
SrAl.sub.2 O.sub.4 : Eu phosphorescent phosphor was actually measured 15 
hours after excitation, it was observed as visually recognizable. 
Table 2 shows the intensity of afterglow of sample 1-(1) which was measured 
10 minutes, 30 minutes and 100 minutes after excitation, respectively, in 
terms of the relative value to the light intensity of ZnS: Cu phosphor. It 
can be seen from Table 2 that the afterglow luminance of SrAl.sub.2 
O.sub.4 : Eu phosphorescent phosphor according to the applied invention, 
measured 10 minutes after excitation, is 2.9 times that of ZnS: Cu 
phosphor, and that the afterglow luminance of SrAl.sub.2 O.sub.4 : Eu 
phosphorescent phosphor according to the present invention, measured 100 
minutes after excitation, is 17 times that of ZnS: Cu phosphor. 
FIG. 4 shows the results of the examination of the thermo-luminescence 
characteristics (glow curves) of SrAl.sub.2 O.sub.4 : Eu phosphorescent 
phosphor according to the applied invention which were measured when the 
phosphorescent phosphor was illuminated in a temperature range between the 
room temperature and 250.degree. C. using a TLD reader (KYOKKO TLD-2000 
system). It can be seen from FIG. 4 that the thermo-luminescence 
characteristics of the phosphorescent phosphor according to the present 
invention have three glow peaks at about 40.degree. C., 90.degree. C. and 
130.degree. C., and that the peak at 130.degree. C. is the main glow peak. 
The glow curve of ZnS: Cu phosphor, indicated by the broken line in FIG. 
4, peak at about 40.degree. C. It is considered that a deep trapping level 
of SrAl.sub.2 O.sub.4 : Eu phosphorescent phosphor according to the 
applied invention, corresponding to a high temperature of 50.degree. C. or 
above, increases the time constant of afterglow, and thus enhances the 
afterglow characteristics over a long time. Samples 1-(2) through 1-(7) 
SrAl.sub.2 O.sub.4 : Eu phosphorescent phosphor samples (sample 1-(2) 
through 1-(7)) having compositions shown in Table 1 were manufactured in 
the same manner as that of sample 1-(1) with the exception that the 
concentration of europium was altered, as shown in Table 1. 
TABLE 1 
______________________________________ 
Material Mixing Ratio 
Strontium 
Sample carbonate Alumina Europium 
______________________________________ 
Sample 1- 
(2) 0.99998 mol 1.0 mol 0.00001 mol 
(3) 0.9999 1.0 0.00005 
(4) 0.995 1.0 0.0025 
(5) 0.97 1.0 0.015 
(6) 0.90 1.0 0.05 
(7) 0.80 1.0 0.1 
______________________________________ 
The results of the examination of the afterglow characteristics of these 
samples 1-(2) through 1-(7), together with those of sample 1-(1), are 
shown in Table 2. 
It can be seen from Table 2 that if the amount of added Eu is between 0.005 
mol and 0.1 mol, the afterglow characteristic of SrAl.sub.2 O.sub.4 is 
more excellent than ZnS: Cu phosphor and the afterglow luminance 10 
minutes after is also more excellent than ZnS: Cu phosphor. Furthermore, 
even when the proportion of Eu is 0.00002 mol or 0.2 mol, afterglow of 
SrAl.sub.2 O.sub.4 : Eu phosphorescent phosphor has a higher luminance 
than that of ZnS: Cu phosphor 30 minutes after excitation ceases. 
Further, since Eu is expensive, if economy and deterioration in the 
afterglow characteristics due to concentration quenching are taken into 
consideration, addition of Eu at a proportion of 0.2 mol (20 mol %) or 
above is meaningless. Conversely, when judging in terms of afterglow 
characteristics, although the luminance of SrAl.sub.2 O.sub.4 10 minutes 
after excitation is lower than ZnS: Cu phosphor when the amount of Eu is 
between 0.00002 mol (0.002 mol %) and 0.0001 mol (0.01 mol %), it has a 
higher luminance than ZnS: Cu phosphor 10 minutes after cessation of 
excitation, thereby indicating that the effect of added Eu as an activator 
is evident. 
Further, since SrAl.sub.2 O.sub.4 : Eu phosphorescent phosphor is an oxide, 
it is chemically stable and shows excellent photo-resistance when compared 
with conventional sulfide phosphors (see Tables 24, 25). 
TABLE 2 
______________________________________ 
Luminance 10 
Luminance 30 
Luminance 100 
Sample minutes after 
minutes after 
minutes after 
______________________________________ 
ZnS: Cu Std. 
1.00 1.00 1.00 
Sample 1- 
(1) 2.90 6.61 17.0 
(2) 0.41 1.20 3.10 
(3) 0.56 1.50 4.80 
(4) 2.40 4.50 13.5 
(5) 3.01 7.04 19.2 
(6) 1.10 2.70 10.3 
(7) 0.32 1.11 3.02 
______________________________________ 
Next, a phosphorescent phosphor which employs strontium as the metal 
element (M) and which employs europium as an activator and dysprosium as a 
co-activator will be described as example 2 of the applied invention. 
Example 2 of the Applied Invention: Synthesis of SrAl.sub.2 O.sub.4 : Eu, 
Dy phosphorescent phosphor and characteristics thereof Sample 2-(1) 
As an activator and as a co-activator, 1.76 g (0.005 mol) of europium oxide 
(Eu.sub.2 O.sub.3) and 1, 87 g (0.005 mol) of dysprosium oxide (Dy.sub.2 
O.sub.3) were added, respectively to 144.6 g (0.98 mol) of strontium 
carbonate having reagent grade and 102 g (1 mol) of alumina having reagent 
grade. Further, for example, 5 g (0.08 mol) of boric acid is added thereto 
as flux. After the resultant mixture was sufficiently mixed using a ball 
mill, the sample was fired for 1 hour at 1300.degree. C. in a stream of 
nitrogen-hydrogen mixture gas (97:3) (flow rate: 0.1 liter/min) using an 
electric furnace. Thereafter, the sample was cooled to a room temperature 
for about 1 hour. The obtained powder compound was sieved having 100 mesh 
to obtain phosphorescent phosphor sample 2-(1). 
The afterglow characteristics of this phosphorescent phosphor were examined 
in the same manner as that described above. The results of the examination 
are shown in sample 2-(1) of FIG. 5 and Table 4. 
As can be seen from FIG. 5, the afterglow luminance of SrAl.sub.2 O.sub.4. 
Eu, Dy phosphorescent phosphor according to the applied invention, 
particularly, the luminance of afterglow at an initial stage thereof is 
much higher than that of ZnS: Cu phosphor, and the decay time constant 
thereof is high. These indicate that SrAl.sub.2 O.sub.4 : Eu, Dy 
phosphorescent phosphor according to the present invention is an 
epoch-making high-luminance phosphorescent phosphor. It can be seen from 
both the visually recognizable afterglow intensity level and the afterglow 
characteristic of this SrAl.sub.2 O.sub.4 : Eu, Dy phosphorescent 
phosphor, shown in FIG. 5, that afterglow of this phosphorescent phosphor 
will be recognized even 16 hours later. 
Table 4 shows the intensity of afterglow of sample 2-(1) which was measured 
10 minutes, 30 minutes and 100 minutes, respectively after excitation in 
terms of the relative value to the afterglow luminescence intensity of 
ZnS: Cu phosphor. It can be seen from Table 4 that the afterglow luminance 
of SrAl.sub.2 O.sub.4 : Eu, Dy phosphorescent phosphor according to the 
applied invention, measured 10 minutes after excitation, is 12.5 times 
that of ZnS: Cu phosphor, and that the afterglow luminance of SrAl.sub.2 
O.sub.4 : Eu, Dy phosphorescent phosphor according to the present 
invention, measured 100 minutes after excitation, is 37 times that of ZnS: 
Cu phosphor. 
FIG. 6 shows the results of the examination of the thermo-luminescence 
characteristics (glow curves) of SrAl.sub.2 O.sub.4 : Eu, Dy 
phosphorescent phosphor according to the applied invention and previously 
irradiated which was conducted in a temperature range between the room 
temperature and 250.degree. C. It can be seen from FIGS. 6 and 4 that 
addition of Dy as a co-activator has changed the main glow peak 
temperature of thermo-luminescence from 130.degree. C. to 90.degree. C. A 
high intensity of emission from the trapping level corresponding to 
90.degree. C. is considered the cause of a higher luminance of afterglow 
at the initial stage thereof than that of SrAl.sub.2 O.sub.4 : Eu 
phosphorescent phosphor. Samples 2-(2) through 2-(7) 
SrAl.sub.2 O.sub.4 : Eu, Dy phosphorescent phosphor samples (sample 2-(2) 
through 2-(7)) having compositions shown in Table 3 were manufactured in 
the same manner as that of sample 2-(1) with the exception that the 
proportion of dysprosium was altered, as shown in Table 3. 
TABLE 3 
______________________________________ 
Material Mixing Ratio 
Sample Strontium carbonate 
Europium Dysprosium 
______________________________________ 
Sample 2- 
(2) 0.98998 mol 
1.1 mol 
0.005 mol 
0.00001 mol 
(3) 0.9899 1.0 0.005 0.00005 
(4) 0.985 1.0 0.005 0.0025 
(5) 0.94 1.0 0.005 0.025 
(6) 0.92 1.0 0.005 0.035 
(7) 0.79 1.0 0.005 0.10 
______________________________________ 
The results of the examination of the afterglow characteristics of these 
samples 2-(2) through 2-(7), together with those of sample 2-(1), are 
shown in Table 4. 
It can be seen from Table 4 that, considering that SrAl.sub.2 O.sub.4 : Eu, 
Dy phosphorescent phosphor has a more excellent afterglow characteristic 
and more excellent luminance 10 minutes after excitation than ZnS: Cu 
phosphor, the optimum proportion of Dy, served as the co-activator, is 
between 0.005 mol to 0.1 mol. However, even when the proportion of Dy is 
0.00002 mol, afterglow of SrAl.sub.2 O.sub.4 : Eu, Dy phosphorescent 
phosphor has a higher luminance than that of ZnS: Cu phosphor 30 minutes 
after excitation ceases. This fact indicates the effects of added Eu and 
Dy as an activator and a co-activator, respectively. Further, since Dy is 
expensive, if economy and deterioration in the afterglow characteristics 
due to concentration quenching are taken into consideration, addition of 
Dy at a proportion of 0.2 mol (20 mol %) or above is meaningless. 
Further, since SrAl.sub.2 O.sub.4 : Eu, Dy phosphorescent phosphor is an 
oxide, it is chemically stable and shows excellent photo-resistance when 
compared with conventional sulfide phosphors (see Tables 24, 25). 
TABLE 4 
______________________________________ 
Luminance Luminance Luminance 
Sample 10 minutes 30 minutes 
100 minutes 
after after after 
______________________________________ 
ZnS: Cu Std 
1.00 1.00 1.00 
Sample 2-(1) 
12.5 19.6 37.0 
Sample 2-(2) 
0.943 1.57 2.00 
Sample 2-(3) 
1.5 1.7 2.1 
Sample 2-(4) 
11.7 17.3 22.1 
Sample 2-(5) 
20.4 28.8 40.2 
Sample 2-(6) 
18.6 26.3 36.4 
Sample 2-(7) 
1.95 2.66 3.30 
______________________________________ 
Next, a phosphorescent phosphor which employs strontium as the metal 
element (M) and which employs europium as an activator and neodymium as a 
co-activator will be described as example 3 of the applied invention. 
Example 3 of the Applied Invention: Synthesis of SrAl.sub.2 O.sub.4 : Eu, 
Nd phosphorescent phosphor and characteristics thereof Samples 3-(1) 
through 3-(7) 
SrAl.sub.2 O.sub.4 : Eu, Nd phosphorescent phosphor samples having 
compositions shown in Table 5 were manufactured in the same manner as that 
described above with the exception that the proportion of neodymium was 
altered, as shown in Table 5. 
TABLE 5 
______________________________________ 
Material Mixing Ratio 
Strontium 
Sample carbonate Alumina Europium 
Neodymium 
______________________________________ 
Sample 3- 
(1) 0.98998 mol 
1.0 mol 0.005 mol 
0.00001 mol 
(2) 0.9899 1.0 0.005 0.00005 
(3) 0.985 1.0 0.005 0.0025 
(4) 0.980 1.0 0.005 0.005 
(5) 0.94 1.0 0.005 0.025 
(6) 0.92 1.0 0.005 0.035 
(7) 0.79 1.0 0.005 0.10 
______________________________________ 
The results of the examination of the afterglow characteristics of these 
samples 3-(1) through 3-(7) are shown in Table 6. 
TABLE 6 
______________________________________ 
Luminance 10 
Luminance 30 
Luminance 100 
Sample minutes after 
minutes after 
minutes after 
______________________________________ 
ZnS: Cu Std. 
1.00 1.00 1.00 
Sample 3- 
(1) 0.71 0.91 1.12 
(2) 0.73 1.02 1.25 
(3) 6.20 8.50 11.14 
(4) 9.05 11.75 14.29 
(5) 9.01 11.55 13.98 
(6) 8.50 10.21 11.96 
(7) 2.35 2.54 2.86 
______________________________________ 
It can be seen from Table 6 that when the amount of added Nd as a 
co-activator is between 0,005 and 0.20 mol, SrAl.sub.2 O.sub.4 : Eu, Nd 
phosphorescent phosphor has a more excellent afterglow characteristic and 
a higher luminance 10 minutes after excitation than ZnS: Cu phosphor. 
However, even when the proportion of Nd is 0.00002 mol, afterglow of 
SrAl.sub.2 O.sub.4 : Eu, Nd phosphorescent phosphor has a higher luminance 
than that of ZnS: Cu phosphor 60 minutes after excitation ceases. This 
fact indicates the effects of added Eu and Nd as an activator and a 
co-activator, respectively. Further, since Nd is expensive, if economy and 
deterioration in the afterglow characteristics due to concentration 
quenching are taken into consideration, addition of Nd at a proportion of 
0.2 mol (20 mol %) or above is meaningless. 
Further, since SrAl.sub.2 O.sub.4 : Eu, Nd phosphorescent phosphor is an 
oxide, it is chemically stable and shows excellent photo-resistance when 
compared with conventional sulfide phosphors (see Tables 24, 25). 
FIG. 7 shows the results of the examination of the thermo-luminescence 
characteristics (glow curves) of SrAl.sub.2 O.sub.4 : Eu, Nd 
phosphorescent phosphor sample 3-(4) according to applied invention and 
previously irradiated which was conducted in a temperature range between 
the room temperature and 250.degree. C. It can be seen from FIG. 7 that 
the main peak temperature of thermo-luminescence of the phosphorescent 
phosphor in which Nd is doped as a co-activator is about 50.degree. C. 
Next, a phosphorescent phosphor which employs strontium as the metal 
element (M), which employs europium as an activator and, which employs, as 
a co-activator, one element selected from a group consisting of lanthanum, 
cerium, praseodymium, samarium, gadolinium, terbium, holmium, erbium, 
thulium, ytterbium, lutetium, manganese, tin, bismuth will be described as 
example 4 of the applied invention. 
In the case of europium, neodymium or dysprosium as an activator or a 
co-activator, addition thereof at a proportion of 0.01 mol relative to the 
metal element (M) assured the high afterglow luminance. With this fact 
taken into consideration, only the samples in which the Eu concentration 
of the activator is 1 mol % (0.01 mol) and the concentration of the 
co-activator is 1 mol % (0.01 mol) are shown. 
Example 4 of Applied Invention: Advantage of doping of another co-activator 
to SrAl.sub.2 O.sub.4 : Eu phosphorescent phosphor 
Table 7 shows the results of the examination of the afterglow 
characteristics of the phosphorescent phosphor samples to which lanthanum, 
cerium, praseodymium, samarium, gadolinium, terbium, holmium, erbium, 
thulium, ytterbium, lutetium, manganese, tin and bismuth were added, 
respectively, as the co-activator. 
As can be seen from Table 7, the afterglow characteristics of any of 
SrAl.sub.2 O.sub.4 : Eu phosphorescent phosphors doped with co-activators, 
improved as the time of more than 30 or 100 minutes elapsed after 
cessation of excitation, as compared with those of currently available 
ZnS: Cu phosphor which was used as the comparison, and were thus at a 
level which allowed the phosphorescent phosphor to be put into practical 
use. 
Since SrAl.sub.2 O.sub.4 : Eu phosphorescent phosphor is an oxide, it is 
chemically stable and shows excellent photo-resistance when compared with 
conventional sulfide phosphors (see Tables 24, 25). 
TABLE 7 
______________________________________ 
Luminance 10 
Luminance 30 
Luminance 100 
Sample minutes after 
minutes after 
minutes after 
______________________________________ 
ZnS: Cu Std 
1.00 1.00 1.00 
SrAl.sub.2 O.sub.4 : Eu, La 
0.33 0.74 1.14 
SrAl.sub.2 O.sub.4 : Eu, Ce 
0.46 0.93 1.35 
SrAl.sub.2 O.sub.4 : Eu, Pr 
1.24 2.63 7.51 
SrAl.sub.2 O.sub.4 : Eu, Sm 
3.40 4.82 9,0 
SrAl.sub.2 O.sub.4 : Eu, Gd 
0.51 1.30 2.27 
SrAl.sub.2 O.sub.4 : Eu, Tb 
1.46 2.81 7,54 
SrAl.sub.2 O.sub.4 : Eu, Ho 
1.06 2.09 6.29 
SrAl.sub.2 O.sub.4 : Eu, Er 
0.63 1.43 3.18 
SrAl.sub.2 O.sub.4 : Eu, Tm 
0.81 1.53 3.28 
SrAl.sub.2 O.sub.4 : Eu, Yb 
0.61 1.28 2.99 
SrAl.sub.2 O.sub.4 : Eu, Lu 
0.49 1.01 3.40 
SrAl.sub.2 O.sub.4 : Eu, Mn 
0.81 1.86 5.57 
SrAl.sub.2 O.sub.4 : Eu, Sn 
1.93 3.61 7.92 
SrAl.sub.2 O.sub.4 : Eu, Bi 
0.72 1.77 5.55 
______________________________________ 
Next, a phosphorescent phosphor, which employs calcium as the metal element 
(M), which employs europium as an activator and which employs no 
co-activator, and a phosphorescent phosphor which employs calcium as the 
metal element, which employs europium as an activator and which employs, 
as a co-activator, at least one element selected from a group consisting 
of lanthanum, cerium, praseodymium, neodymium, samarium, gadolinium, 
terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, 
manganese, tin and bismuth will be described below as example 5 of the 
applied invention. 
Example 5 of the Applied Invention: Synthesis of CaAl.sub.2 O.sub.4 : Eu 
phosphorescent phosphor and characteristics thereof 
Europium oxide (Eu.sub.2 O.sub.3) as an activator was doped to calcium 
carbonate having reagent grade and alumina having reagent grade and 5 g 
(0.08 mol) of boric acid was doped thereto as flux. 
Europium oxide (Eu.sub.2 O.sub.3) and either of lanthanum oxide, cerium 
oxide, praseodymium oxide, neodymium oxide, samarium oxide, gadolinium 
oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, 
thulium oxide, ytterbium oxide, lutetium oxide, manganese oxide, tin oxide 
and bismuth oxide were added, as an activator and a co-activator 
respectively, to calcium carbonate having reagent grade and alumina having 
reagent grade and 5 g (0.08 mol) of boric acid was added thereto as flux. 
After the resultant mixture was sufficiently mixed using a ball mill, the 
sample was fired for 1 hour at 1300.degree. C. in a stream of 
nitrogen-hydrogen mixture gas (97:3) (flow rate: 0.1 liter/min) using an 
electric furnace. Thereafter, the sample was cooled to a room temperature 
for about 1 hour. The obtained powder compound was sieved having 100 mesh 
to obtain phosphorescent phosphor sample 5-(1) through 5-(42). 
FIG. 8 shows the results of analysis of the crystal structure of the 
obtained sample 5-(2) by XRD. It was discovered from the diffraction peak 
characteristics that the obtained phosphorescent phosphor was monoclinic 
CaAl.sub.2 O.sub.4. 
FIGS. 9A, 9B, and 10A and 10B respectively show the results of the 
examination of the thermo-luminescence characteristics (glow curves) of 
samples 5-(10), 5-(16), 5-(22) and 5-(28) which employed, as the 
co-activator, neodymium, samarium, dysprosium, and thulium, respectively. 
In either case, the glow curve has a peak in the high-temperature range of 
50.degree. C. or above. This implies that these phosphorescent phosphors 
have long-lasting afterglow characteristics. The emission spectrum of 
afterglow of each of the samples had a peak at about 442 nm, as shown in 
FIG. 11, and the color of afterglow was thus blue. 
The afterglow characteristics of each of the samples were relatively 
compared with the afterglow characteristics of currently available CaSrS: 
Bi phosphorescent phosphor which emitted light of blue (manufactured by 
Nemoto Co., LTD trademark: BA-S, and the wavelength of emission peak: 454 
nm) in Tables 8 through 13. As is apparent from Table 8, when the 
proportion of Eu in CaAl.sub.2 O.sub.4 : Eu phosphorescent phosphor is 
0.01 mol (1.0 mol %), although the luminance of afterglow at an initial 
stage thereof is low, it increases substantially to that of the currently 
available phosphorescent phosphor 100 minutes after cessation of 
excitation. As shown in Tables 9 through 13, addition of a co-activator 
further increased the afterglow luminance. This happened whichever type of 
co-activator was employed. Particularly, addition of Nd, Sm and Tm was 
greatly effective, and thus provided a super high luminance blue emission 
color phosphorescent phosphor which was an order of magnitude brighter. 
FIG. 12 shows the results of the examination of the long-lasting afterglow 
of these high-luminance phosphorescent phosphors obtained by adding Nd, Sm 
and Tm as a co-activator. 
In more detail, Table 8 shows the afterglow characteristics of 
phosphorescent phosphors which employ calcium and europium as the metal 
element (M) and the activator, respectively, and which employ no 
co-activator, the phosphorescent phosphors being shown in 5-(1) through 
5(6). 
TABLE 8 
______________________________________ 
Lumi- Lumi- 
nance nance 
10 30 Luminance 
minutes minutes 100 minutes 
Sample after after after 
______________________________________ 
Std. CaSrS: Bi 1.00 1.00 1.00 
5-(1) CaAl.sub.2 O.sub.4 : Eu (Eu: 0.001 mol %) 
0.18 0.16 0.14 
5-(2) CaAl.sub.2 O.sub.4 : Eu (Eu: 0.01 mol %) 
0.21 0.18 0.17 
5-(3) CaAl.sub.2 O.sub.4 : Eu (Eu: 0.1 mol %) 
0.25 0.27 0.35 
5-(4) CaAl.sub.2 O.sub.4 : Eu (Eu: 0.5 mol %) 
0.41 0.60 0.90 
5-(5) CaAl.sub.2 O.sub.4 : Eu (Eu: 2.5 mol %) 
0.37 0.45 0.65 
5-(6) CaAl.sub.2 O.sub.4 : Eu (Eu: 10 mol %) 
0.25 0.28 0.39 
______________________________________ 
Table 9 shows the afterglow characteristics of phosphorescent phosphors 
which employ calcium, europium and neodymium as the metal element (M), the 
activator, and the co-activator, respectively, the phosphorescent 
phosphors being shown in 5-(7) through 5-(12). 
TABLE 9 
______________________________________ 
Lumi- 
nance 
10 Luminance Luminance 
minutes 30 minutes 
100 minutes 
Sample after after after 
______________________________________ 
Std. CaSrS: Bi 1.00 1.00 1.00 
5-(7) CaAl.sub.2 O.sub.4 : Eu, Nd 
0.53 0.78 1.01 
(Eu: 0.5 mol % Nd: 0.001 mol %) 
5-(8) CaAl.sub.2 O.sub.4 : Eu, Nd 
1.05 1.53 2.60 
(Eu: 0.5 mol % Nd: 0.01 mol %) 
5-(9) CaAl.sub.2 O.sub.4 : Eu, Nd 
8.68 11.8 20.3 
(Eu: 0.5 mol % Nd: 0.1 mol %) 
5-(10) CaAl.sub.2 O.sub.4 : Eu, Nd 
9.87 14.0 25.0 
(Eu: 0.5 mol % Nd: 0.5 mol %) 
5-(11) CaAl.sub.2 O.sub.4 : Eu, Nd 
3.18 4.51 8.05 
(Eu: 0.5 mol % Nd: 2.5 mol %) 
5-(12) CaAl.sub.2 O.sub.4 : Eu, Nd 
0.84 1.18 2.02 
(Eu: 0.5 mol % Nd: 10 mol %) 
______________________________________ 
Table 10 shows the afterglow characteristics of phosphorescent phosphors 
which employ calcium, europium and samarium as the metal element (M), the 
activator, and the co-activator, respectively, the phosphorescent 
phosphors being shown in 5-(13) through 5-(18). 
TABLE 10 
______________________________________ 
Lumi- 
nance 
10 Luminance Luminance 
minutes 30 minutes 
100 minutes 
Sample after after after 
______________________________________ 
Std. CaSrS: Bi 1.00 1.00 1.00 
5-(13) CaAl.sub.2 O.sub.4 : Eu, Sm 
0.71 0.98 1.23 
(Eu: 0.5 mol % Sm: 0.001 mol %) 
5-(14) CaAl.sub.2 O.sub.4 : Eu, Sm 
0.94 1.43 2.55 
(Eu: 0.5 mol % Sm: 0.01 mol %) 
5-(15) CaAl.sub.2 O.sub.4 : Eu, Sm 
4.21 6.32 11.30 
(Eu: 0.5 mol % Sm: 0.1 mol %) 
5-(16) CaAl.sub.2 O.sub.4 : Eu, Sm 
4.61 7.00 12.5 
(Eu: 0.5 mol % Sm: 0.5 mol %) 
5-(17) CaAl.sub.2 O.sub.4 : Eu, Sm 
2.14 3.25 5.80 
(Eu: 0.5 mol % Sm: 2.5 mol %) 
5-(18) CaAl.sub.2 O.sub.4 : Eu, Sm 
0.63 0.96 1.71 
(Eu: 0.5 mol % Sm: 10 mol %) 
______________________________________ 
Table 11 shows the afterglow characteristics of phosphorescent phosphors 
which employ calcium, europium and dysprosium as the metal element (M), 
the activator, and the co-activator, respectively, the phosphorescent 
phosphors being shown in 5-(19) through 5-(24). 
TABLE 11 
______________________________________ 
Lumi- 
nance 
10 Luminance Luminance 
minutes 30 minutes 
100 minutes 
Sample after after after 
______________________________________ 
Std. CaSrS: Bi 1.00 1.00 1.00 
5-(19) CaAl.sub.2 O.sub.4 : Eu, Dy 
0.30 0.24 0.20 
(Eu: 0.5 mol % Dy: 0.001 mol %) 
5-(20) CaAl.sub.2 O.sub.4 : Eu, Dy 
0.41 0.39 0.35 
(Eu: 0.5 mol % Dy: 0.01 mol %) 
5-(21) CaAl.sub.2 O.sub.4 : Eu, Dy 
0.52 0.60 0.76 
(Eu: 0.5 mol % Dy: 0.1 mol %) 
5-(22) CaAl.sub.2 O.sub.4 : Eu, Dy 
0.76 0.90 1.25 
(Eu: 0.5 mol % Dy: 0.5 mol %) 
5-(23) CaAl.sub.2 O.sub.4 : Eu, Dy 
0.84 1.18 1.76 
(Eu: 0.5 mol % Dy: 2.5 mol %) 
5-(24) CaAl.sub.2 O.sub.4 : Eu, Dy 
0.50 0.58 0.76 
(Eu: 0.5 mol % Dy:10 mol %) 
______________________________________ 
Table 12 shows the afterglow characteristics of phosphorescent phosphors 
which employ calcium, europium and thulium as the metal element (M), the 
activator, and the co-activator, respectively, the phosphorescent 
phosphors being shown in 5-(25) through 5-(30). 
TABLE 12 
______________________________________ 
Lumi- 
nance 
10 Luminance Luminance 
minutes 30 minutes 
100 minutes 
Sample after after after 
______________________________________ 
Std. CaSrS: Bi 1.00 1.00 1.00 
5-(25) CaAl.sub.2 O.sub.4 : Eu, Tm 
1.04 1.36 1.81 
(Eu: 0.5 mol % Dy: 0.001 mol %) 
5-(26) CaAl.sub.2 O.sub.4 : Eu, Tm 
2.09 2.65 3.75 
(Eu: 0.5 mol % Tm: 0.01 mol %) 
5-(27) CaAl.sub.2 O.sub.4 : Eu, Tm 
4.89 5.78 8.70 
(Eu: 0.5 mol % Tm: 0.1 mol %) 
5-(28) CaAl.sub.2 O.sub.4 : Eu, Tm 
6.55 9.04 18.6 
(Eu: 0.5 mol % Tm: 0.5 mol %) 
5-(29) CaAl.sub.2 O.sub.4 : Eu, Tm 
0.634 1.19 2.68 
(Eu: 0.5 mol % Tm: 2.5 mol %) 
5-(30) CaAl.sub.2 O.sub.4 : Eu, Tm 
0.151 0.358 0.755 
(Eu: 0.5 mol % Tm:10 mol %) 
______________________________________ 
Table 13 shows the afterglow characteristics of phosphorescent phosphors 
which employ calcium, europium and either of lanthanum, cerium, 
praseodymium, gadolinium, terbium, holmium, erbium, ytterbium, iutetium, 
manganese, tin and bismuth as the metal element (M), the activator, and 
the co-activator, respectively, the phosphorescent phosphors being shown 
in 5-(31) through 5-(42). 
1 mol % of europium as the activator and another co-activator were each 
doped to the phosphorescent phosphors shown in 5-(31) through 5-(42). 
TABLE 13 
______________________________________ 
Lumi- 
nance 
10 Luminance Luminance 
minutes 30 minutes 
100 minutes 
Sample after after after 
______________________________________ 
Std. CaSrS: Bi 1.00 1.00 1.00 
(31) CaAl.sub.2 O.sub.4 : Eu, La 
0.52 0.67 0.81 
(Eu: 0.5 mol % La: 0.5 mol %) 
(32) CaAl.sub.2 O.sub.4 : Eu, Ce 
0.84 1.23 1.96 
(Eu: 0.5 mol % Ce: 0.5 mol %) 
(33) CaAl.sub.2 O.sub.4 : Eu, Pr 
0.5 0.82 1.13 
(Eu: 0.5 mol % Pr: 0.5 mol %) 
(34) CaAl.sub.2 O.sub.4 : Eu, Gd 
0.66 0.91 1.26 
(Eu: 0.5 mol % Gd: 0.5 mol %) 
(35) CaAl.sub.2 O.sub.4 : Eu, Tb 
0.84 1.31 2.08 
(Eu: 0.5 mol % Tb: 0.5 mol %) 
(36) CaAl.sub.2 O.sub.4 : Eu, Ho 
0.98 1.33 2.39 
(Eu: 0.5 mol % Ho: 0.5 mol %) 
(37) CaAl.sub.2 O.sub.4 : Eu, Er 
0.56 0.76 0.98 
(Eu: 0.5 mol % Er: 0.5 mol %) 
(38) CaAl.sub.2 O.sub.4 : Eu, Yb 
0.70 0.91 1.28 
(Eu: 0.5 mol % Yb: 0.5 mol %) 
(39) CaAl.sub.2 O.sub.4 : Eu, Lu 
0.68 0.90 1.24 
(Eu: 0.5 mol % Lu: 0.5 mol %) 
(40) CaAl.sub.2 O.sub.4 : Eu, Mn 
0.31 0.42 0.58 
(Eu: 0.5 mol % Mn: 0.5 mol %) 
(41) CaAl.sub.2 O.sub.4 : Eu, Sn 
0.45 0.58 0.73 
(Eu: 0.5 mol % Sn: 0.5 mol %) 
(42) CaAl.sub.2 O.sub.4 : Eu, Bi 
0.25 0.33 0.48 
(Eu: 0.5 mol % Bi: 0.5 mol %) 
______________________________________ 
Next, a phosphorescent phosphor which employs, calcium europium and 
neodymium as the metal element (M), the activator and the co-activator, 
respectively while another co-activator is added thereto at the same time 
will be described as example 6. 
Example 6 of Applied Invention Synthesis of CaAl.sub.2 O.sub.4 : Eu, Nd 
phosphorescent phosphor and characteristics thereof 
Europium oxide (Eu.sub.2 O.sub.3) as an activator and neodynrium as a 
co-activator were added to calcium carbonate having reagent grade and 
alumina having reagent grade and 5 g (0.08 mol) of boric acid was added 
thereto as flux. 
Europium oxide (Eu.sub.2 O.sub.3) as an activator, neodymium as a 
co-activator, and further, either of lanthanum oxide, cerium oxide, 
praseodymium oxide, samarium oxide, gadolinium oxide, terbium oxide, 
dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium 
oxide, lutetium oxide, manganese oxide, tin oxide and bismuth oxide except 
neodymium oxide as another co-activator were doped to calcium carbonate 
having reagent grade and alumina having reagent grade and 5 g (0.08 mol) 
of boric acid was added thereto as flux. After the resultant mixture was 
sufficiently mixed using a ball mill, the sample was fired for 1 hour at 
1300.degree. C. in a stream of nitrogen-hydrogen mixture gas (97:3) (flow 
rate: 0.1 liter/min) using an electric furnace. Thereafter, the sample was 
cooled to a room temperature for about 1 hour. The obtained powder 
compound was sieved having 100 mesh to obtain phosphorescent phosphor 
sample 6-(1) through 6-(43). 
Various samples were manufactured with 1 mol % of Eu, 1 mol % of Nd and 1 
mol % of another co-activator and the afterglow luminances 10 minutes, 30 
minutes and 100 minutes after excitation were measured. Table 14 shows the 
results in 6-(1) through 6-(15). 
TABLE 14 
______________________________________ 
Lumi- 
nance 
10 
minutes Luminance 30 
Luminance 100 
Sample after minutes after 
minutes after 
______________________________________ 
Std. CaSrS: Bi 1.0 1.0 1.0 
CaAl.sub.2 O.sub.4 : Eu, Nd 
9.87 14.0 25.0 
6-(1) CaAl.sub.2 O.sub.4 : Eu, Nd, La 
20.6 23.2 29.5 
(2) CaAl.sub.2 O.sub.4 : Eu, Nd, Ce 
12.7 17.5 26.9 
(3) CaAl.sub.2 O.sub.4 : Eu, Nd, Pr 
13.3 18.1 27.7 
(4) CaAl.sub.2 O.sub.4 : Eu, Nd, Sm 
8.20 12.6 22.6 
(5) CaAl.sub.2 O.sub.4 : Eu, Nd, Gd 
16.7 21.3 33.5 
(6) CaAl.sub.2 O.sub.4 : Eu, Nd, Tb 
13.8 17.2 25.5 
(7) CaAl.sub.2 O.sub.4 : Eu, Nd, Dy 
14.8 18.9 30.8 
(8) CaAl.sub.2 O.sub.4 : Eu, Nd, Ho 
16.5 21.6 34.3 
(9) CaAl.sub.2 O.sub.4 : Eu, Nd, Er 
15.9 21.0 33.8 
(10) CaAl.sub.2 O.sub.4 : Eu, Nd, Tm 
4.17 6.69 13.4 
(11) CaAl.sub.2 O.sub.4 : Eu, Nd, Yb 
11.0 16.9 27.9 
(12) CaAl.sub.2 O.sub.4 : Eu, Nd, Lu 
10.2 15.2 25.2 
(13) CaAl.sub.2 O.sub.4 : Eu, Nd, Mn 
6.45 8.01 11.9 
(14) CaAl.sub.2 O.sub.4 : Eu, Nd, Sn 
11.4 14.1 21.2 
(15) CaAl.sub.2 O.sub.4 : Eu, Nd, Bi 
10.6 13.5 21.4 
______________________________________ 
It was recognized from the result of the measurement that the co-activators 
doped together with neodymium which have a particularly. excellent 
afterglow luminance, were lanthanum, dysprosium, gadolinium, holmium, 
erbium and the like. 
Then, with 1 mol % of Eu and 1 mol % of Nd, the concentration of lanthanum 
was changed from 0.2 mol % to 20 mol %. Table 15 shows the result of the 
experiment in 6-(16) through 6-(21). 
TABLE 15 
__________________________________________________________________________ 
Luminance 10 
Luminance 30 
Luminance 100 
Sample minutes after 
minutes after 
minutes after 
__________________________________________________________________________ 
Std. CaSrS: Bi 1.0 1.0 1.0 
(16) CaAl.sub.2 O.sub.4 : Eu, Nd 
9.87 14.0 25.0 
(Eu: 0.5 mol % Nd: 0.5 mol %) 
(17) CaAl.sub.2 O.sub.4 : Eu, Nd, La 
14.1 18.2 29.3 
(Eu: 0.5 mol % Nd: 0.5 mol % La: 0.1 mol %) 
(18) CaAl.sub.2 O.sub.4 : Eu, Nd, La 
15.5 18.9 28.S 
(Eu: 0.5 mol % Nd: 0.5 mol % La: 0.3 mol %) 
(1) CaAl.sub.2 O.sub.4 : Eu, Nd, La 
20.6 23.2 29.5 
(Eu: 0.5 mol % Nd: 0.5 mol % La: 0.5 mol %) 
(19) CaAl.sub.2 O.sub.4 : Eu, Nd,La 
1.42 1.05 0.858 
(Eu: 0.5 mol % Nd: 0.5 mol % La: 1.0 mol %) 
(20) CaAl.sub.2 O.sub.4 : Eu, Nd, La 
Measurement Limit 
(Eu: 0.5 mol % Nd: 0.5 mol % Ca: 2.0 mol %) 
(21) CaAl.sub.2 O.sub.4 : Eu, Nd, La 
Measurement Limit 
(Eu: 0.5 mol % Nd: 0.5 mol % La: 10 mol %) 
__________________________________________________________________________ 
With 1 mol % of Eu and 1 mol % of Nd, the concentration of dysprosium was 
changed from 0.2 mol % to 20 mol %. Table 16 shows the result of the 
experiment in 6-(22) through 6-(27). 
TABLE 16 
__________________________________________________________________________ 
Luminance 10 
Luminance 30 
Luminance 100 
Sample minutes after 
minutes after 
minutes after 
__________________________________________________________________________ 
Std. CaSrS: Bi 1.0 1.0 1.0 
(22) CaAl.sub.2 O.sub.4 : Eu, Nd 
9.87 14.0 25.0 
(Eu: 0.5 mol % Nd: 0.5 mol %) 
(23) CaAl.sub.2 O.sub.4 : Eu, Nd, Dy 
4.32 6.76 12.0 
(Eu: 0.5 mol % Nd: 0.5 mol % Dy: 0.1 mol %) 
(24) CaAl.sub.2 O.sub.4 : Eu, Nd, Dy 
8.91 14.0 24.2 
(Eu: 0.5 mol % Nd: 0.5 mol % Dy: 0.3 mol %) 
(7) CaAl.sub.2 O.sub.4 : Eu, Nd, Dy 
14.8 18.9 30.8 
(Eu: 0.5 mol % Nd: 0.5 mol % Dy: 0.5 mol %) 
(25) CaAl.sub.2 O.sub.4 : Eu, Nd, Dy 
12.1 18.3 27.8 
(Eu: 0.5 mol % Nd: 0.5 mol % Dy: 1.0 mol %) 
(26) CaAl.sub.2 O.sub.4 : Eu, Nd, Dy 
(Eu: 0.5 mol % Nd: 0.5 mol % Dy: 2.0 mol %) 
7.49 10.3 16.0 
(27) CaAl.sub.2 O.sub.4 : Eu, Nd, Dy 
1.84 1.29 0.998 
(Eu: 0.5 mol % Nd: 0.5 mol % Dy: 10 mol %) 
__________________________________________________________________________ 
With 1 mol % of Eu and 1 mol % of Nd, the concentration of gadolinium was 
changed from 0.2 mol % to 20 mol %. Table 17 shows the result of the 
experiment in 6-(28) through 6-(32). 
TABLE 17 
__________________________________________________________________________ 
Luminance 10 
Luminance 30 
Luminance 100 
Sample minutes after 
minutes after 
minutes after 
__________________________________________________________________________ 
Std. CaSrS: Bi 1.0 1.0 1.0 
CaAl.sub.2 O.sub.4 : Eu, Nd 
9.87 14.0 25.0 
(Eu: 0.5 mol % Nd: 0.5 mol %) 
(28) CaAl.sub.2 O.sub.4 : Eu, Nd, Gd 
11.8 17.4 30.0 
(Eu: 0.5 mol % Nd: 0.5 mol % Gd: 0.1 mol %) 
(29) CaAl.sub.2 O.sub.4 : Eu, Nd, Gd 
12.7 17.8 29.8 
(Eu: 0.5 mol % Nd; 0.5 mol % Gd: 0.3 mol %) 
(5) CaAl.sub.2 O.sub.4 : Eu, Nd, Gd 
16.7 21.3 33.S 
(Eu: 0.5 mol % Nd: 0.5 mol % Gd: 0.5 mol %) 
(30) CaAl.sub.2 O.sub.4 : Eu, Nd, Gd 
10.8 15.7 26.5 
(Eu: 0.5 ml% Nd: 0.5 mol % Gd: 1.0 mol %) 
(31) CaAl.sub.2 O.sub.4 : Eu, Nd, Gd 
18.0 21.7 29.5 
(Eu: 0.5 mol % Nd: 0.5 mol % Gd: 2.0 mol %) 
(32) CaAl.sub.2 O.sub.4 : Eu, Nd, Gd 
1.01 0.764 0.590 
(Eu: 0.5 mol % Nd: 0.5 mol % Gd: 10 mol %) 
__________________________________________________________________________ 
With 1 mol % of Eu and 1 mol % of Nd, the concentration of holmium was 
changed from 0.2 mol % to 20 mol %. Table 18 shows the result of the 
experiment in 6-(33) through 6-(37). 
TABLE 18 
__________________________________________________________________________ 
Luminance 10 
Luminance 30 
Luminance 100 
Sample minutes after 
minutes after 
minutes after 
__________________________________________________________________________ 
Std. CaSrS: Bi 1.0 1.0 1.0 
CaAl.sub.2 O.sub.4 : Eu, Nd 
9.87 14.0 25.0 
(Eu: 0.5 mol % Nd: 0.5 mol %) 
(33) CaAl.sub.2 O.sub.4 : Eu, Nd, Ho 
10.4 14.4 25.3 
(Eu: 0.5 mol % Nd: 0.5 mol % Nd: 0.1 mol %) 
(34) CaAl.sub.2 O.sub.4 : Eu, Nd, Ho 
12.0 16.2 27.0 
(Eu: 0.5 mol % Nd: 0.5 mol % Ho: 0.3 mol %) 
(8) CaAl.sub.2 O.sub.4 : Eu, Nd, Ho 
16.5 21.6 34.3 
(Eu: 0.5 mol % Nd: 0.5 mol % Ho 0.5 mol %) 
(35) CaAl.sub.2 O.sub.4 : Eu, Nd, Ho 
13.4 16.9 26.3 
(Eu: 0.5 mol % Nd: 0.5 mol % Ho: 1.0 mol %) 
(36) CaAl.sub.2 O.sub.4 : Eu, Nd, Ho 
13.3 16.0 23.S 
(Eu: 0.5 mol % Nd: 0.5 mol % Ho: 2.0 mol %) 
(37) CaAl.sub.2 O.sub.4 : Eu, Nd, Ho 
1.20 0.914 0.782 
(Eu: 0.5 mol % Nod: 0.5 mol % Ho: 10 mol %) 
__________________________________________________________________________ 
With 1 mol % of Eu and 1 mol % of Nd, the concentration of erbium was 
changed from 0.2 mol % to 10 mol %. Table 19 shows the result of the 
experiment in 6-(38) through 6-(43). 
TABLE 19 
__________________________________________________________________________ 
Luminance 10 
Luminance 30 
Luminance 100 
Sample minutes after 
minutes after 
minutes after 
__________________________________________________________________________ 
Std. CaSrS: Bi 1.0 1.0 1.0 
CaAl.sub.2 O.sub.4 : Eu, Nd 
9.87 14.0 25.0 
(Eu; 0.5 mol % Nd: 0.5 mol %) 
(38) CaAl.sub.2 O.sub.4 : Eu, Nd, Er 
10.7 15.1 27.0 
(Eu: 0.5 mol % Nd: 0.5 mol % Er: 0.1 mol %) 
(39) CaAl.sub.2 O.sub.4 : Eu, Nd, Er 
10.3 14.0 24.0 
(Eu: 0.5 mol % Nd: 0.5 mol % Er: 0.3 mol %) 
(9) CaAl.sub.2 O.sub.4 : Eu, Nd, Er 
15.9 21.0 33.8 
(Eu: 0.5 mol % Nd; 0.5 mol % Er, 0.5 mol %) 
(40) CaAl.sub.2 O.sub.4 : Eu, Nd, Er 
16.4 21.1 32.3 
(Eu: 0.5 mol % Nd: 0.5 mol % Er: 1.0 mol %) 
(41) CaAl.sub.2 O.sub.4 : Eu, Nd, Er 
17.3 21.7 30.8 
(Eu: 0.5 mal % Id: 0.5 mol % Er: 2.0 mol %) 
(42) CaAl.sub.2 O.sub.4 : Eu, Nd, Er 
20.1 21.3 28.5 
(Eu: 0.5 ml % Nd: 0.5 mol % Er: 3.0 mol %) 
(43) CaAl.sub.2 O.sub.4 : Eu, Nd, Er 
17.5 17.8 22.0 
(Eu: 0.5 mol % Nd: 0.5 mol % Er: 5.0 mol %) 
__________________________________________________________________________ 
It was recognized from the results of the measurements that certain 
mixtures of the co-activators improved the afterglow luminance. Further, 
it was also recognized that the sample had the most excellent afterglow 
characteristics when, with 1 mol % of Eu and 1 mol % of Nd, about 1 mol % 
of another co-activator was added. 
Next, a phosphorescent phosphor which employs barium, europium and 
neodymium as the metal element (M), an activator and a co-activator, 
respectively, will be described as example 7 of the applied invention. 
Example 7 of Applied Invention BaAl.sub.2 O.sub.4 : Eu phosphorescent 
phosphor 
After 1 mol % of Eu was added to the phosphorescent phosphor, further 1 mol 
% of Nd or Sm was added thereto. The results are shown in 7-(1) and 7-(2). 
FIGS. 13A and 13B respectively shows the excitation spectrum of the 
phosphorescent phosphor which employs neodymium as the co-activator and 
the afterglow emission spectrum thereof obtained 30 minutes after 
excitation is ceased. 
FIGS. 14A and 14B respectively show the excitation spectrum of the 
phosphorescent phosphor which employs samarium as the co-activator and the 
afterglow emission spectrum thereof obtained 30 minutes after excitation 
is ceased. 
The peak wavelength of emission spectrum is always about 500 nm, the 
emission spectrum emitting light of green. Table 20 shows the results of 
the comparison between the afterglow characteristics of the obtained 
BaAl.sub.2 O.sub.4 : Eu phosphorescent phosphor and those of ZnS: Cu 
phosphor which is available on the market and which emits light of green 
(manufactured by Nemoto & Co., LTD. GSS, and the wavelength of emission 
peak: 530 nm), indicating relative values of the afterglow intensities 10 
minutes, 30 minutes and 100 minutes after excitation is ceased. 
TABLE 20 
______________________________________ 
Lumi- 
nance Luminance 
10 30 
minutes minutes Luminance 100 
Sample after after minutes after 
______________________________________ 
Std.ZnS: Cu 1.0 1.0 1.0 
BaAl.sub.2 O.sub.4 : Eu, Nd 
1.23 1.14 0.885 
(Eu: 0.5 mol % Nd: 0.5 mol %) 
BaAl.sub.2 O.sub.4 : Eu, Sm 
0.982 0.911 0.768 
(Eu: 0.5 mol % Sm: 0.5 mol %) 
______________________________________ 
Table 20 shows that BaAl.sub.2 O.sub.4 : Eu, Nd has a more excellent 
afterglow luminance than ZnS: Cu phosphor for about 30 minutes after 
excitation is ceased. It was found that BaAl.sub.2 O.sub.4 : Eu, Sm had a 
little lower afterglow luminance than ZnS: Cu phosphor. However, it has 
been confirmed that no fluorescence or afterglow is recognized as a result 
of experiments with only BaAl.sub.2 O.sub.4 crystal without adding Eu or 
other co-activator thereto. Therefore, it is evident that the effects of 
activation can be assured by doping Eu, Nd or Sm to BaAl.sub.2 O.sub.4 
phosphorescent phosphor. 
Since BaAl.sub.2 O.sub.4 : Eu phosphorescent phosphor is an oxide, it is 
chemically stable and shows excellent photo-resistance when compared with 
conventional sulfide phosphors (see Tables 24, 25). 
Next, a phosphorescent phosphor which employs, as the metal element(M), a 
mixture of calcium and strontium will be described as example 8 of the 
applied invention. 
Example 8 of Applied Invention Synthesis of Sr.sub.x Ca.sub.1-x Al.sub.2 
O.sub.4 phosphorescent phosphor and characteristics thereof 
Strontium carbonate having reagent grade and calcium carbonate having 
reagent grade were mixed with each other at different ratios. Alumina was 
added to each of the obtained samples. Also, europium and either of 
lanthanum, cerium, praseodymium, neodymium, samarium, gadolinium, terbium, 
dysprosium, holmium, erbium, thulium, ytterbium, lutetium, manganese, tin 
and bismuth were added to each of the samples as the activator and the 
co-activator, respectively, and additionally, 5 g (0.08 mol) of boric acid 
was added thereto as flux to obtain Sr.sub.x Ca.sub.1-x Al.sub.2 O.sub.4 
phosphorescent phosphor samples in the manner described above. 
FIG. 15 shows the results of the examination of the afterglow emission 
spectrum of Sr0.5Ca0.5Al.sub.2 O.sub.4 : Eu, Dy phosphorescent phosphor 
(Eu 1 mol %, Dy 1 mol %). It is apparent from FIG. 15 that when Ca is 
substituted for a part of Sr, the emission wavelength is reduced and thus 
produces an afterglow having a color between that obtained by emission of 
SrAl.sub.2 O.sub.4 phosphorescent phosphor and that obtained by emission 
of CaAl.sub.2 O.sub.4 phosphorescent phosphor. 
FIG. 16 shows the results of the examination of the afterglow 
characteristics of Sr.sub.x Ca.sub.1-x Al.sub.2 O.sub.4 phosphorescent 
phosphor samples in which 1 mol % of Eu and 1 mol % of Dy were added as 
the activator and the co-activator, respectively. 
As can be seen from FIG. 16, any of these phosphorescent phosphors shows 
excellent afterglow characteristics and is thus practically applicable as 
compared with the currently available phosphorescent phosphors shown by 
the broken line in FIG. 16. 
Next, a phosphorescent phosphor which employs, as the metal element (M), a 
mixture of strontium and barium will be described as example 9 of the 
applied invention. 
Example 9 of Applied Invention Synthesis of Sr.sub.x Ba.sub.1-x Al.sub.2 
O.sub.4 phosphorescent phosphor and characteristics thereof 
Strontium carbonate having reagent grade and barium carbonate having 
reagent grade were mixed with each other at different ratios. Alumina was 
added to each of the obtained samples. Also, europium and either of 
lanthanum, cerium, praseodymium, neodymium, samarium, gadolinium, terbium, 
dysprosium, holmium, erbium, thulium, ytterbium, lutetium, manganese, tin 
and bismuth were added to each of the samples as the activator and the 
co-activator, respectively, and 5 g (0.08 mol) of boric acid was added 
thereto as flux to obtain Sr.sub.x Ba.sub.1-x Al.sub.2 O.sub.4 
phosphorescent phosphor samples in the manner described above. 
FIG. 17 shows the results of the examination of the afterglow 
characteristics of Sr.sub.x Ba.sub.1-x Al.sub.2 O.sub.4 phosphorescent 
phosphors to which 1 mol % of Eu and 1 mol % of Dy were added. 
As can be seen from FIG. 17, any of these phosphorescent phosphors shows 
excellent afterglow characteristics and is thus practically applicable as 
compared with the currently available phosphor shown by the broken line in 
FIG. 17. 
Next, a phosphorescent phosphor which employs, as the metal element (M), a 
mixture of strontium and magnesium will be described as example 10 of the 
applied invention. 
Example 10 of Applied Invention Synthesis of Sr.sub.x Mg.sub.1-x Al.sub.2 
O.sub.4 phosphorescent phosphor and characteristics thereof 
Strontium carbonate having reagent grade and magnesium carbonate having 
reagent grade were mixed with each other at different ratios. Alumina was 
added to each of the obtained samples. Also, europium and either of 
lanthanum, cerium, praseodymium, neodymium, samarium, gadolinium, terbium, 
dysprosium, holmium, erbium, thulium, ytterbium, lutetium, manganese, tin, 
and bismuth were added to each of the samples as the activator and the 
co-activator, respectively, and additionally, 5 g (0.08 mol) of boric acid 
was added thereto as flux to obtain Sr.sub.x Mg.sub.1-x Al.sub.2 O.sub.4 
phosphorescent phosphor samples in the manner described above. 
FIG. 18 shows the results of the examination of the afterglow 
characteristics of Sr.sub.x Mg.sub.1-x Al.sub.2 O.sub.4 phosphorescent 
phosphors to which 1 mol % of Eu and 1 mol % of Dy were added. 
As can be seen from FIG. 18, any of these phosphorescent phosphors shows 
excellent afterglow characteristics and is thus practically applicable 
except for the phosphorescent phosphors in which the ratio between 
strontium and magnesium was 0.1/0.9, as compared with the currently 
available phosphorescent phosphor shown by the broken line in FIG. 18. 
Next, a phosphorescent phosphor which employs a plurality of metal elements 
and europium as the metal element (M) and an activator, respectively and 
further two types of co-activators, will be described as example 11 of the 
applied invention. 
Example 11 of Applied Invention Synthesis of Ca.sub.1-x Sr.sub.x Al.sub.2 
O.sub.4 : Eu, Nd, X phosphorescent phosphor and characteristics thereof. 
Strontium carbonate having reagent grade and calcium carbonate having 
reagent grade were mixed with each other at different ratios. Alumina was 
added to each of the obtained samples. Also, 1 mol % of europium, 1 mol % 
of neodymium and further, 1 mol % of either of lanthanum, dysprosium and 
holmium were added to each of the samples as the activator, the 
co-activator and another co-activator, respectively, and 5 g (0.08 mol) of 
boric acid was added thereto as flux to obtain Ca.sub.1-x Sr.sub.x 
Al.sub.2 O.sub.4 : Eu, Nd, X phosphorescent phosphor samples 11-(1) 
through 11-(9) in the manner described above. Then, the afterglow 
characteristics of the samples were examined. 
Strontium carbonate having reagent grade and calcium carbonate having 
reagent grade were mixed with each other at different ratios. Alumina was 
added to each of the obtained samples. Also, 1 mol % of europium, 1 mol % 
of neodymium and further, 1 mol % of lanthanum were added to each of the 
samples as the activator, the co-activator and another co-activator, 
respectively, to obtain the samples 11-(1) through 11-(3) shown in Table 
21. 
TABLE 21 
______________________________________ 
Lumi- Lumi- 
nance nance Luminance 
10 30 100 
minutes minutes minutes 
Sample after after after 
______________________________________ 
Std.CaSrS: Bi 1.0 1.0 1.0 
CaAl.sub.2 O.sub.4 : Eu, Nd 
9.87 14.0 25.0 
11-(1) (Ca.sub.0.9 SR.sub.0.1)Al.sub.2 O.sub.4 : Eu, Nd, 
15.2 17.1 19.0 
.sup. (2) (Ca.sub.0.7 SR.sub.0.3)Al.sub.2 O.sub.4 : Eu, Nd, 
5.53 4.96 3.35 
.sup. (3) (Ca.sub.0.5 SR.sub.0.5)Al.sub.2 O.sub.4 : Eu, Nu, 
6.30 3.08 Measure- 
ment 
limit 
______________________________________ 
Strontium carbonate having reagent grade and calcium carbonate having 
reagent grade were mixed with each other at different ratios. Alumina was 
added to each of the obtained samples. Also, 1 mol % of europium, 1 mol % 
of neodymium and further, 1 mol % of dysprosium were added to each of the 
samples as the activator, the co-activator and another co-activator, 
respectively, to obtain the samples 11-(4) through 11-(6) shown in Table 
22. 
TABLE 22 
______________________________________ 
Lumi- Lumi- 
nance nance Luminance 
10 30 100 
minutes minutes minutes 
Sample after after after 
______________________________________ 
Std.CaSrS: Bi 1.0 1.0 1.0 
CaAl.sub.2 O.sub.4 : Eu, Nd 
9.87 14.0 25.0 
(4) (Ca.sub.0.9 Sr.sub.0.1)Al.sub.2 O.sub.4 : Eu, Nd, Dy 
13.2 14.6 20.4 
(5) (Ca.sub.0.7 Sr.sub.0.3)Al.sub.2 O.sub.4 : Eu, Nd, Dy 
8.00 7.46 9.05 
(6) (Ca.sub.0.5 Sr.sub.0.5)Al.sub.2 O.sub.4 : Eu, Nd, Dy 
3.36 3.08 Measurement 
limit 
______________________________________ 
Strontium carbonate having reagent grade and calcium carbonate having 
reagent grade were mixed with each other at different ratios. Alumina was 
added to each of the obtained samples. Also, 1 mol % of europium, 1 mol % 
of neodymium and further, 1 mol % of holmium were added to each of the 
samples as the activator, the co-activator and another co-activator, 
respectively, to obtain the samples 11-(7) through 11-(9) shown in Table 
23. 
TABLE 23 
______________________________________ 
Lumi- Lumi- 
nance nance Luminance 
10 30 100 
minutes minutes minutes 
Sample after after after 
______________________________________ 
Std.CaSrS: Bi 1.0 1.0 1.0 
CaAl.sub.2 O.sub.4 : Eu, Nd 
9.87 14.0 25.0 
(7) (Ca.sub.0.9 Sr.sub.0.1)Al.sub.2 O.sub.4 : Eu, Nd, Ho 
13.9 15.3 21.4 
(8) (Ca.sub.0.7 Sr.sub.0.3)Al.sub.2 O.sub.4 : Eu, Nd, Ho 
8.25 7.81 9.95 
(9) (Ca.sub.0.5 Sr.sub.0.5)Al.sub.2 O.sub.4 : Eu, Nd, Ho 
2.91 2.62 3.65 
______________________________________ 
As can be seen from the results of the measurement, the phosphorescent 
phosphors which employ calcium and strontium as the metal element (M), 
employ europium as the activator and employ a plurality of co-activators 
shows excellent afterglow characteristics than CaSrS: Bi and further the 
luminance 10 minutes after excitation was more excellent than CaSrS: Bi. 
Example 12 of Applied Invention Humidity test 
Table 24 shows the results of the examination of moisture resistance 
characteristics of phosphorescent phosphor obtained according to the 
present invention. 
In the humidity test, a plurality of phosphorescent phosphor samples were 
left for 500 hours in a constant temperature and humidity bath which was 
adjusted to 40.degree. C. and 95% RH, and the resultant changes in the 
luminance of each of the samples were measured. 
As can be seen from Table 24, none of the samples was affected by humidity 
and the samples were thus stable. 
TABLE 24 
______________________________________ 
Sample Before test 
After test 
______________________________________ 
SrAl.sub.2 O.sub.4 : Eu, Dy 
1.0 1.01 
(Eu: 0.5 mol % Dy: 0.5 mol %) 
CaAl.sub.2 O.sub.4 : Eu, Nd 
1.0 0.99 
(Eu: 0.5 mol % Nd: 0.5 mol %) 
Sr0.5Ca0.5Al.sub.2 O.sub.4 : Eu, Dy 
1.0 1.00 
(Eu: 0.5 mol % Dy: 0.5 mol %) 
Sr0.5Ba0.5Al.sub.2 O.sub.4 : Eu, Dy 
1.0 0.99 
(Eu: 0.5 mol % Dy: 0.5 mol %) 
Sr0.5Mg0.5Al.sub.2 O.sub.4 : Eu, Dy 
1.0 1.02 
(Eu: 0.5 mol % Dy: 0.5 mol %) 
______________________________________ 
Example 13 of Applied Invention Photo resistance test 
FIG. 25 shows the results of the photo resistance test conducted on the 
phosphorescent phosphors according to the present invention together with 
the results obtained from zinc sulfide phosphor. 
This test was conducted conforming to JIS standard on the sample placed in 
a transparent container whose humidity was adjusted to saturated humidity 
by irradiating the sample by a mercury lamp of 300 W located at 30 cm 
above the sample for 3 hours, 6 hours and 12 hours, respectively, and by 
measuring changes in the luminance caused by irradiation. 
As can be seen from Table 25, phosphorescent phosphors according to the 
present invention are very stable as compared with conventional zinc 
sulfide phosphor. 
TABLE 25 
______________________________________ 
Before 3 hours 6 hours 
12 hours 
Sample test after after after 
______________________________________ 
Std. ZnS: Cu 1.0 0.91 0.82 0.52 
SrAl.sub.2 O.sub.4 : Eu, Dy 
1.0 1.01 1.00 1.01 
(Eu: 0.5 mol % Dy: 0.5 mol %) 
CaAl.sub.2 O.sub.4 : Eu, Nd 
1.0 1.00 1.01 1.00 
(Eu: 0.5 mol % Nd: 0.5 mol %) 
Sr.sub.0.5 Ca.sub.0.5 Al.sub.2 O.sub.4 : Eu, Dy 
1.0 1.00 0.99 1.00 
(Eu: 0.5 mol % Dy: 0.5 mol %) 
Sr.sub.0.5 Ba.sub.0.5 Al.sub.2 O.sub.4 : Eu, Dy 
1.0 1.01 1.01 1.01 
(Eu: 0.5 mol % Dy: 0.5 mol %) 
Sr.sub.0.5 Mg.sub.0.5 Al.sub.2 O.sub.4 : Eu, Dy 
1.0 1.00 1.00 0.99 
(Eu: 0.5 mol % Dy: 0.5 mol %) 
______________________________________ 
The foregoing phosphorescent phosphor is made of the novel phosphorescent 
phosphor material, which is completely different from the materials of the 
conventional sulfide phosphors. The foregoing phosphorescent phosphor 
exhibits afterglow characteristics lasting for a considerably longer time 
and higher luminance as compared with those of the conventional phosphors, 
and furthermore chemically stable because the phosphorescent phosphor is 
made of an oxide substance and exhibits excellent photo-resistance. 
The phosphorescent phosphor according to the applied invention and 
expressed as MAl.sub.2 O.sub.4 is not limited to the composition in which 
M, Al and O are accurately contained as 1:2:4. The ratio can accidently be 
out of the foregoing value by a somewhat degree due to any of a variety of 
conditions. As a matter of course, the somewhat deviation of the ratio is 
within the range of the foregoing applied invention so far as the 
foregoing effects can be obtained. 
Accordingly, the applicant of the present invention measured the luminance 
of phosphorescent phosphors respectively arranged to have intentionally 
deviated ratios. 
As a result, a fact was found that excellent afterglow luminance could be 
sometimes realized even if the foregoing ratio was not satisfied. 
SUMMARY OF THE INVENTION 
In view of the foregoing, an object of the present invention is to provide 
a phosphorescent phosphor of a type having a composition in which M, Al 
and O are contained at an optimum ratio among phosphorescent phosphors 
exhibiting afterglow characteristics lasting for a considerably longer 
time and significantly higher luminance as compared with the currently 
available phosphor, and is chemically stable because the phosphorescent 
phosphor is made of an oxide substance and having excellent 
photo-resistance. 
In order to achieve the foregoing object, according to claim 1 of the 
present invention, there is provided a phosphorescent phosphor comprising 
a matrix and having a composition expressed by M.sub.1-x Al.sub.2 
O.sub.4-x (except X=0) in which M is at least one metal element selected 
from a group consisting of calcium, strontium and barium, wherein europium 
is doped to said matrix as an activator and at least one element selected 
from a group consisting of lanthanum, cerium, praseodymium, neodymium, 
samarium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, 
ytterbium and lutetium is doped to said matrix as a co-activator. 
According to claim 2 of the present invention, a phosphorescent phosphor 
according to claim 1 is that X is in a range -0.33.ltoreq.x.ltoreq.0.60 
(except x=0). 
According to claim 3 of the present invention, a phosphorescent phosphor 
according to claim 1 is that 0,002% to 20% of europium is doped to said 
matrix as an activator in terms of mol % relative to the metal element 
expressed by M. 
According to claim 4 of the present invention, a phosphorescent phosphor 
according to claims 1 
is that 0,002% to 20% of at least one element selected from a group 
consisting of lanthanum, cerium, praseodymium, neodymium, samarium, 
gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, 
lutetium is doped to said matrix as a co-activator in terms of mol % 
relative to the metal element expressed by M. 
According to claim 5 of the present invention, there is provided a 
phosphorescent phosphor according to claim 1 that magnesium is doped to M. 
According to claim 6 of the present invention, there is provided a 
phosphorescent phosphor according to claim 2 that 0.002% to 20% of 
europium is doped to the matrix as an activator in terms of mol % relative 
to the metal element expressed by M. 
According to claim 7 of the present invention, there is provided a 
phosphorescent phosphor according to claim 2 that 0.002% to 20% of at 
least one element selected from a group consisting of lanthanum, cerium, 
praseodymium, neodymium, samarium, gadolinium, terbium, dysprosium, 
holmium, erbium, thulium, ytterbium, lutetium is doped to the matrix as a 
co-activator in terms of mol % relative to the metal element expressed by 
M. 
According to claim 8 of the present invention, there is provided a 
phosphorescent phosphor according to claim 6 that 0.002% to 20% of at 
least one element selected from a group consisting of lanthanum, cerium, 
praseodymium, neodymium, samarium, gadolinium, terbium, dysprosium, 
holmium, erbium, thulium, ytterbium, lutetium is doped to the matrix as a 
co-activator in terms of mol % relative to the metal element expressed by 
M. 
According to claim 9 of the present invention, there is provided a 
phosphorescent phosphor according to claim 2 that magnesium is doped to M. 
According to claim 10 of the present invention, there is provided a 
phosphorescent phosphor according to claim 6 that magnesium is doped to M. 
According to claim 11 of the present invention, there is provided a 
phosphorescent phosphor according to claim 8 that magnesium is doped to M. 
According to claim 12 of the present invention, there is provided a 
phosphorescent phosphor according to claim 3 that 0.002% to 20% of at 
least one element selected from a group consisting of lanthanum, cerium, 
praseodymium, neodymium, samarium, gadolinium, terbium, dysprosium, 
holmium, erbium, thulium, ytterbium, lutetium, manganese, tin and bismuth 
is doped to the matrix as a co-activator in terms of mol % relative to the 
metal element expressed by M. 
According to claim 13 of the present invention, there is provided a 
phosphorescent phosphor according to claim 3 that magnesium is doped to M. 
According to claim 14 of the present invention, there is provided a 
phosphorescent phosphor according to claim 4 that magnesium is doped to M. 
According to claim 15 of the present invention, there is provided a 
phosphorescent phosphor according to claim 7 that magnesium is doped to M.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A phosphorescent phosphor having a composition expressed by M.sub.1-x 
Al.sub.2 O.sub.4-x will now be described as Sr.sub.1-x Al.sub.2 O.sub.4-x 
: Eu, Dy in which strontium is used as the metal element (M), europium is 
used as the activator, and dysprosium is used as the co-activator. 
The concentration of doped Eu and Dy was 0.01 mol with respect to the 
quantity of strontium. 
The ratios of strontium and aluminum, the values of X and the 
phosphorescent phosphor samples (1) to (8) were as follows: 
EQU Sr:Al=1:1.5 X=-0.33 Sr.sub.1.33 Al.sub.2 O.sub.5.33 :Eu, Dy(1) 
EQU Sr:Al=1:1.9 X=-0.05 Sr.sub.1.05 Al.sub.2 O.sub.4.05 :Eu, Dy(2) 
EQU Sr:Al=1:2.0 X=0 Sr.sub.1.00 Al.sub.2 O.sub.4.00 :Eu, Dy (3) 
EQU Sr:Al=1:2.1 X=0.05 Sr.sub.0.95 Al.sub.2 O.sub.3.95 :Eu, Dy (4) 
EQU Sr:Al=1:2.5 X=0.20 Sr.sub.0.80 Al.sub.2 O.sub.3.80 :Eu, Dy (5) 
EQU Sr:Al=1:3.0 X=0.33 Sr.sub.0.67 Al.sub.2 O.sub.3.67 :Eu, Dy (6) 
EQU Sr:Al=1:4.0 X=0.50 Sr.sub.0.50 Al.sub.2 O.sub.3.50 :Eu, Dy (7) 
EQU Sr:Al=1:5.0 X=0.60 Sr.sub.0.40 Al.sub.2 O.sub.3.40 :Eu, Dy (8) 
The samples (1) to (8) were temporarily brought to a non afterglow state, 
and then the samples were allowed to stand at room temperature for 20 
minutes. Then, the luminance attained three minutes after was visually 
measured. In the foregoing state, the afterglow luminance was subjected to 
a comparison with that attained in a case where X=0 was made to be 100. 
Table 26 shows the results. 
TABLE 26 
______________________________________ 
Sample Luminance 
______________________________________ 
(1) Sr.sub.1.33 Al.sub.2 O.sub.5.33 : Eu, Dy 
10 
(2) Sr.sub.1.05 Al.sub.2 O.sub.4.05 : Eu, Dy 
45 
(3) Sr.sub.1.00 Al.sub.2 O.sub.4.00 : Eu, Dy 
100 
(4) Sr.sub.0.95 Al.sub.2 O.sub.3.95 : Eu, Dy 
100 
(5) Sr.sub.0.80 Al.sub.2 O.sub.3.80 : Eu, Dy 
110 
(6) Sr.sub.0.67 Al.sub.2 O.sub.3.67 : Eu, Dy 
90 
(7) Sr.sub.0.50 Al.sub.2 O.sub.3.50 : Eu, Dy 
60 
(8) Sr.sub.0.40 Al.sub.2 O.sub.3.40 : Eu, Dy 
30 
______________________________________ 
As can be understood from Table 26, the afterglow luminance of samples (1) 
and (2) was inferior to that of sample (3), which was SrAl.sub.2 O.sub.4 : 
Eu, Dy and in which X=0. However, samples (4) to (6) had afterglow 
luminance equivalent or superior to that of sample (3). 
Samples (1) to (5) enabled phosphorescent phosphors each having the 
fluorescent spectrum peak at about 520 nm and emitting green fluorescent 
light to be obtained. 
Samples (6) to (8) enabled phosphorescent phosphors each having the 
fluorescent spectrum peak at about 490 nm and emitting blue green 
fluorescent light to be obtained. 
Thus, if the phosphorescent phosphor containing strontium as the metal 
element (M), europium serving as the activator and dysprosium serving as 
the co-activator satisfies -0.33.ltoreq.X.ltoreq.0.60 when the 
phosphorescent phosphor is expressed as Sr.sub.1-x Al.sub.2 O.sub.4-x : 
Eu, Dy, practically high afterglow luminance could be obtained, more 
preferably 0.ltoreq.X.ltoreq.0.33. 
To obtain blue green fluorescent light, a suitable range being 
0.33.ltoreq.X.ltoreq.0.60 was understood from the foregoing experiment 
data. Furthermore, even if the foregoing range was met, afterglow 
luminance raising no practical problem was observed. 
Then, a phosphorescent phosphor having a composition expressed by M.sub.1-x 
Al.sub.2 O.sub.4-x of a type containing calcium as the metal element (M), 
europium serving as the activator and dysprosium serving as the 
co-activator and in the form of Ca.sub.1-x Al.sub.2 O.sub.4-x : Eu, Dy 
will now be described. 
The concentration of doped Eu and Dy was 0.01 mol with respect to the 
quantity of calcium. 
The ratios of calcium and aluminum, the values of X and the phosphorescent 
phosphor samples (1) to (8) were as follows: 
EQU Ca:Al=1:1.5 X=-0.33 Ca.sub.1.33 Al.sub.2 O.sub.5.33 :Eu, Dy(1) 
EQU Ca:Al=1:1.9 X=-0.05 Ca.sub.1.05 Al.sub.2 O.sub.4.05 :Eu, Dy(2) 
EQU Ca:Al=1:2.0 X=0 Ca.sub.1.00 Al.sub.2 O.sub.4.00 :Eu, Dy (3) 
EQU Ca:Al=1:2.1 X=0.05 Ca.sub.0.95 Al.sub.2 O.sub.3.95 :Eu, Dy (4) 
EQU Ca:Al=1:2.5 X=0.20 Ca.sub.0.80 Al.sub.2 O.sub.3.80 :Eu, Dy (5) 
EQU Ca:Al=1:3.0 X=0.33 Ca.sub.0.67 Al.sub.2 O.sub.3.67 :Eu, Dy (6) 
EQU Ca:Al=1:4.0 X=0.50 Ca.sub.0.50 Al.sub.2 O.sub.3.50 :Eu, Dy (7) 
EQU Ca:Al=1:5.0 X=0.60 Ca.sub.0.40 Al.sub.2 O.sub.3.40 :Eu, Dy (8) 
The samples (1) to (8) were temporarily brought to a non afterglow state, 
and then the samples were allowed to stand at room temperature for 20 
minutes. Then, the luminance attained three minutes after was visually 
measured. In the foregoing state, the afterglow luminance was subjected to 
a comparison with that attained in a case where X=0 was made to be 100. 
Table 27 shows the results. 
TABLE 27 
______________________________________ 
Sample Luminance 
______________________________________ 
(1) Ca.sub.1.33 Al.sub.2 O.sub.5.33 : Eu, Dy 
70 
(2) Ca.sub.1.05 Al.sub.2 O.sub.4.05 : Eu, Dy 
90 
(3) Ca.sub.1.00 Al.sub.2 O.sub.4.00 : Eu, Dy 
100 
(4) Ca.sub.0.95 Al.sub.2 O.sub.3.95 : Eu, Dy 
80 
(5) Ca.sub.0.80 Al.sub.2 O.sub.3.80 : Eu, Dy 
40 
(6) Ca.sub.0.67 Al.sub.2 O.sub.3.61 : Eu, Dy 
20 
(7) Ca.sub.0.50 Al.sub.2 O.sub.3.50 : Eu, Dy 
15 
(8) Ca.sub.0.40 Al.sub.2 O.sub.3.40 : Eu, Dy 
10 
______________________________________ 
As can be understood from Table 27, the afterglow luminance of samples (1), 
(2) and (4) to (6) was inferior to that of sample (3), which was 
CaAl.sub.2 O.sub.4 : Eu, Dy and in which X=0, but the foregoing samples 
were satisfactorily used. 
Thus, if the phosphorescent phosphor containing calcium as the metal 
element (M), europium serving as the activator and dysprosium serving as 
the co-activator satisfies -0.33.ltoreq.X.ltoreq.0.60 when the 
phosphorescent phosphor is expressed as Ca.sub.1-x Al.sub.2 O.sub.4-x : 
Eu, Dy, practically high afterglow luminance could be obtained, more 
preferably -0.33.ltoreq.X.ltoreq.0.05. 
Then, a phosphorescent phosphor having a composition expressed by M.sub.1-x 
Al.sub.2 O.sub.4-x of a type containing barium as the metal element (M), 
europium serving as the activator and dysprosium serving as the 
co-activator and in the form of Sr.sub.1-x Al.sub.2 O.sub.4-x : Eu, Dy 
will now be described. 
The concentration of doped Eu and Dy was 0.01 mol with respect to the 
quantity of calcium. 
The ratios of barium and aluminum, the values of X and the phosphorescent 
phosphor samples (1) to (7) were as follows: 
EQU Ba:Al=1:1.5 X=-0.33 Ba.sub.1.33 Al.sub.2 O.sub.5.33 :Eu, Dy(1) 
EQU Ba:Al=1:1.9 X=-0.05 Ba.sub.1.05 Al.sub.2 O.sub.4.05 :Eu, Dy(2) 
EQU Ba:Al=1:2.1 X=0.05 Ba.sub.0.95 Al.sub.2 O.sub.3.95 :Eu, Dy (3) 
EQU Ba:Al=1:2.5 X=0.20 Ba.sub.0.80 Al.sub.2 O.sub.3.80 :Eu, Dy (4) 
EQU Ba:Al=1:3.0 X=0.33 Ba.sub.0.67 Al.sub.2 O.sub.3.67 :Eu, Dy (5) 
EQU Ba:Al=1:4.0 X=0.50 Ba.sub.0.50 Al.sub.2 O.sub.3.50 :Eu,Dy (6) 
EQU Ba:Al=1:5.0 X=0.60 Ba.sub.0.40 Al.sub.2 O.sub.3.40 :Eu, Dy (7) 
The samples (1) to (7) were temporarily brought to a non afterglow state, 
and then the samples were allowed to stand at room temperature for 20 
minutes. Then, the luminance attained three minutes after was visually 
measured. In the foregoing state, the afterglow luminance was subjected to 
a comparison with that attained in a case where X=0 was made to be 100. 
Table 28 shows the results. 
TABLE 28 
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Sample Luminance 
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(1) Ba.sub.1.33 Al.sub.2 O.sub.5.33 : Eu, Dy 
10 
(2) Ba.sub.1.05 Al.sub.2 O.sub.4.05 : Eu, Dy 
20 
(3) Ba.sub.0.95 Al.sub.2 O.sub.3.95 : Eu, Dy 
100 
(4) Ba.sub.0.80 Al.sub.2 O.sub.3.80 : Eu, Dy 
110 
(5) Ba.sub.0.67 Al.sub.2 O.sub.3.67 : Eu, Dy 
105 
(6) Ba.sub.0.5 0Al.sub.2 O.sub.3.50 : Eu, Dy 
70 
(7) Ba.sub.0.40 Al.sub.2 O.sub.3.40 : Eu, Dy 
50 
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As can be understood from Table 28, the afterglow luminance of samples (1) 
and (2) was inferior to that of sample (3), which was Ba.sub.0.95 Al.sub.2 
O.sub.3.95 : Eu,Dy and in which X=2.1, but samples (4) and (5) had 
afterglow characteristics somewhat higher than that of sample (3). 
Furthermore, samples (6) and (7) could be used practically. 
Thus, if the phosphorescent phosphor containing barium as the metal element 
(M), ouropium serving as the activator and dysprosium serving as the 
co-activator satisfies -0.33.ltoreq.X.ltoreq.0.60 when the phosphorescent 
phosphor is expressed as Ba.sub.1-x Al.sub.2 O.sub.4-x : Eu, Dy, 
practically high afterglow luminance could be obtained, more preferably 
0.05.ltoreq.X.ltoreq.0.50. 
Even if the ratio of ouropium serving as the activator and the dysprosium 
serving as the co-activator was changed in each of the examples, a similar 
tendency was confirmed by the applicant of the present invention. 
Furthermore, in the case where magnesium was doped to strontium, calcium 
and barium as the metal element (M), if the compound having the 
composition expressed by M.sub.1-x Al.sub.2 O.sub.4-x met 
-0.33.ltoreq.X.ltoreq.0.60, afterglow luminance which was satisfactory in 
the viewpoint of practical use was attained. 
In a case where 0.002% to 20% of at least one element selected from a group 
consisting of lanthanum, cerium, praseodymium, neodymium, samarium, 
gadolinium, terbium, holmium, erbium, thulium, ytterbium, lutetium, 
manganese, tin and bismuth is doped as a co-activator in terms of mol % 
relative to the metal element expressed by M in addition to dysprosium 
serving as the co-activator, if X of a compound having a composition 
expressed by M.sub.1-x Al.sub.2 O.sub.4-x satisfied 
-0.33.ltoreq.X.ltoreq.0.60, afterglow luminance which was satisfactory in 
the viewpoint of practical use was attained. 
In the case where calcium and barium were employed as the metal element 
(M), even if the ratio of europium serving as the activator and the 
dysprosium serving as the co-activator was changed in each of the 
examples, a similar tendency was confirmed by the applicant of the present 
invention. 
Furthermore, in the case where magnesium was doped to strontium, calcium 
and barium as the metal element (M), if the compound having the 
composition expressed by M.sub.1-x Al.sub.2 O.sub.4-x met 
-0.33.ltoreq.X.ltoreq.0.60, afterglow luminance which was satisfactory in 
the viewpoint of practical use was attained. 
In a case where at least one element selected from a group consisting of 
lanthanum, cerium, praseodymium, neodymium, samarium, gadolinium, terbium, 
holmium, erbium, thulium, ytterbium, lutetium, manganese, tin and bismuth 
is doped as a co-activator in terms of mol % relative to the metal element 
expressed by M in addition to dysprosium, if X of a compound having a 
composition expressed by M.sub.1-x Al.sub.2 O.sub.4-x satisfied 
-0.33.ltoreq.X.ltoreq..ltoreq.0.60, afterglow luminance which was 
satisfactory in the viewpoint of practical use was attained. 
For use, the foregoing phosphorescent phosphor may be coated on the surface 
of any of various products or may be formed into a sheet-like shape so as 
to be applied for use. It may also be mixed into a plastic material, 
rubber or glass. 
Also, phosphorescent phosphor according to the present invention may 
replace conventional sulfide phosphors. The phosphorescent phosphor 
according to the present invention will show excellent characteristics in 
applying it to various gauges, dial plates of clocks, and safety signs, 
due to the long-lasting high-luminance afterglow characteristics thereof. 
The phosphorescent phosphor according to the present invention can be 
employed in any of the following applications, because it has excellent 
long-lasting high luminance afterglow characteristics and because it is an 
oxide and hence chemically stable and shows excellent photo-resistance. 
Indicator for vehicles: airplane, ship, automobile, bicycle, key, key hole 
Indicator for signs: traffic sign, indicator of traffic lanes, indicator 
for a guard rail, fishing buoy, direction board on a maintain trail, 
direction board which guides a guest from a gate to a front door, 
indication on helmet 
Outdoor indicator: signboard, indicator for buildings, indicator for the 
key hole of automobile, 
Indoor indicator: electrical appliance switches 
Stationery: writing instruments, luminous ink, map, star chart 
Toys: Jigsaw puzzle 
Special usage: sports ball, fishing tackles, threads, cloths, back-light 
for liquid crystal (for use in, for example, clock), replacement of 
isotope used for discharge tube 
As described above, the present invention relates to a novel phosphorescent 
phosphor which is completely different from well-known sulfide phosphors, 
and has much longer high-luminance afterglow characteristics as compared 
with sulfide phosphors which are available on the market. Further, the 
phosphorescent phosphor according to the present invention is chemically 
stable because it is an oxide and has excellent photo-resistance. Among 
phosphorescent phosphors exhibiting excellent photo-resistance, a 
phosphorescent phosphor containing M, Al and O at an optimum ratio can be 
provided.