JP2000212557A - Luminous phosphor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a luminous phosphor activated with bivalent europium, having a specific chemical compositional formula, thus attaining long afterglow time/high afterglow luminance compared to conventional silicate-based luminous phosphors, presenting diversified luminescent colors ranging from blue to yellowish green colors, therefore useful for e.g. night signs. SOLUTION: This luminous phosphor is such one as to be activated with bivalent europium and have a chemical composition of the formula (R is at least one element selected from the group consisting of Ca, Sr and Ba; M is a coactivator, being at least one element selected from the group consisting of Nb, Zr, Bi, Mn, Sn, In, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc and Y; 0.4<=(a)<=0.9; 0.00001<=b<=0.30; 0.25<=c <=1.5; 0.00001<=d<=0.2; 0.00001<=e<=0.2; 0<=x<1.0; 0<=y< 1.0). This luminous phosphor is obtained by the following process: appropriate amounts of respective specified stocks are weighed, mixed together, put into an alumina crucible, and then burned at 950-1,500 deg.C for 1-12 h in a reductive atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is activated by divalent europium and has a chemical composition formula of aRO. (1-a) (Mg
_1-x Zn _x ) O.bAl ₂ O ₃ .c (Si _1-y Ge _y ) O _2.
dEu · eM (where R is at least one member selected from the group consisting of Ba, Sr, and Ca, M is a coactivator,
Nb, Zr, Bi, Mn, Sn, In, La, Ce, P
r, Nd, Sm, Gd, Tb, Dy, Ho, Er, T
at least one member selected from the group consisting of m, Yb, Lu, Sc, and Y), and has a long afterglow time, a high afterglow luminance, and various emission wavelengths.

[0002]

2. Description of the Related Art Fluorescence is a phenomenon in which a substance emits light in the vicinity of the visible region due to an external stimulus (excitation), such as light emitted from a fluorescent lamp, discharge lamp, CRT (Cathode Ray Tube), a so-called cathode ray tube, or the like. A substance that emits fluorescence is referred to as a phosphor.
When the fluorescence continues for about 1 second), this is called phosphorescence. Further, a phosphor having a long afterglow such that phosphorescence lasts for several hours at room temperature is called a phosphorescent phosphor.

[0003] A sulfide-based phosphorescent phosphor represented by ZnS: Cu, which has been put into practical use as a phosphorescent phosphor and is currently the mainstream, is used. The ZnS: Cu sulfide phosphorescent phosphor has been in practical use for several decades, but has a problem that the afterglow time is as short as about 3 hours at most. Further, the phosphorescent phosphor of the ultraviolet contained in sunlight and, due to moisture contained in the atmosphere, phosphorescent article itself is blackened _{ZnS + H 2 O → Zn +} H 2 S becomes decomposition reaction occurs, the afterglow function in a short period of time It has the fatal drawback of being significantly reduced. Furthermore, in order to make up for the short afterglow time, a radioactive substance may be contained in some cases, which has a disadvantage that it is harmful to the human body and the environment. For this reason, this kind of phosphorescent phosphor has been mainly used for very limited applications such as luminous clocks and indoor nighttime displays.

Recently, new phosphorescent phosphors mainly composed of silicates have been disclosed (JP-A-9-194833, JP-A-9-2416).
No. 31) was developed. Compared with the conventional sulfide-based phosphor, this phosphorescent phosphor has such characteristics that it has high afterglow luminance, a long afterglow time, and is excellent in chemical durability because it is an oxide. Therefore, in addition to the existing applications such as luminous clocks and indoor nighttime display, a wide range of applications such as disaster prevention signs, danger prevention displays for position recognition, and decorative articles can be expected.

[0005]

As the field of application of the phosphorescent phosphor has been expanded, it is necessary to improve the characteristics as required. Among them, further improvement in afterglow luminance and afterglow time is strongly desired.

[0006]

The present invention SUMMARY OF] In order to solve the above problems, activated with divalent europium, the chemical composition formula aRO · (1-a) ( Mg 1-x Zn x) O · bA
l ₂ O ₃ · c (Si _{1 -y} Ge _y ) O ₂ · dEu · eM (where R is at least one member selected from the group consisting of Ba, Sr and Ca, M is a coactivator and Nb , Zr, B
i, Mn, Sn, In, La, Ce, Pr, Nd, S
m, Gd, Tb, Dy, Ho, Er, Tm, Yb, L
at least one member selected from the group consisting of u, Sc, and Y).

The silicate phosphorescent phosphor (JP-A-9-19)
No. 4833) is mainly composed of okermanite (C
mineral called _{a 2 Mg (Si 2 O 7} )), the crystal structure is made a double pyramid and MgO ₄ tetrahedra with O share (Si ₂ MgO ₇₎ layer of Si ₂ O _7, Ca between layers 8 It is in the configuration. Sr and Ba can form a solid solution at the Ca position between the layers, and have the same structure as that of akermanite. On the other hand, a mineral called gehlenite (Ca ₂ Al (AlSiO ₇ )) is generally known. This crystal structure is (Al, Si)
_{The two} pyramids of ₂ O ₇ and the AlO ₄ tetrahedron share O (Si
Al ₂ O ₇₎ layer structure, Ca is contained in 8 coordination between the layers. Sr and Ba can also form a solid solution at the Ca position between the layers, and have the same structure as that of gehlenite. A crystal structure in which Al is continuously dissolved as a solid with these two crystal phases as end components is called melilite. That is, the bipyramid of (Al, Si) ₂ O ₇ and the (Mg, Al) O ₄ tetrahedron share O ((S
i, Al, Mg) ₃ O ₇ ) layers, and Ca, Sr,
Ba enters in 8-coordination. We have found a phosphorescent phosphor that can solve the problem by using this melilite-type structure as a mother crystal and divalent europium as an activator, and have completed the present invention.

That is, the phosphorescent phosphor according to claim 1 is activated by divalent europium, and its chemical composition is aRO · (1-a) (Mg _1-x Zn _x ) O · bAl ₂ O _3.
c (Si _1-y Ge _y ) O ₂ .dEu.eM (where R is B
a, Sr, and Ca are at least one selected from the group consisting of M, M is a co-activator, and Nb, Zr, Bi, Mn, S
n, In, La, Ce, Pr, Nd, Sm, Gd, T
b, Dy, Ho, Er, Tm, Yb, Lu, Sc, and Y). a, b, c, d, e, x, and y are each 0. 4 ≦ a ≦ 0.9, 0.00001 ≦ b <0.30, 0.25 ≦ c ≦ 1.5, 0.00001 ≦ d ≦ 0.2, 0.00001 ≦ e ≦ 0.2, 0 ≦ A phosphorescent phosphor characterized by being in the range of x <1.0, 0 ≦ y <1.0.

In the phosphorescent phosphor of the present invention, a is RO
(Where R is selected from the group consisting of Ba, Sr, and Ca
(At least one type), and (1-a) is Mg
The composition ratio of O and / or ZnO, b is Al_TwoO_ThreePair of
Where c is SiO_TwoAnd / or GeO_TwoThe composition ratio of
It is shown. When the range of a, b, c is 0.4 ≦ a ≦
0.9, 0.00001 ≦ b <0.30, 0.25 ≦ c
≦ 1.5, Merilite type structure, high afterglow brightness
A phosphorescent phosphor having a long afterglow time can be obtained. To R
By changing the ratio of Ba, Sr, and Ca,
Luminescent phosphor with a wide range of emission colors from blue to yellow-green
You. Specifically, Sr alone emits blue light, and Sr
By gradually substituting Ca, the emission wavelength shifts to the longer wavelength side.
The emission wavelength is shortened by gradually replacing Sr with Ba.
Shift to the wavelength side. Also, Al _TwoO_ThreeThe composition ratio of
Can also shift the emission wavelength.
The phosphorescent phosphor having a desired emission color can be obtained.
Wear.

D indicates the concentration of the activator and is 0.00
001 ≦ d ≦ 0.2. d <
At 0.00001, light absorption becomes poor and sufficient afterglow luminance cannot be obtained. Conversely, when d> 0.2, concentration quenching occurs, and the afterglow luminance decreases. Preferably, 0.00005 ≦ d ≦
0.1, particularly preferably 0.0001 ≦ d ≦ 0.05
Range.

E represents the concentration of the co-activator, and is 0.0
0001 ≦ e ≦ 0.2. e <
At 0.00001, the effect of increasing the afterglow time and the afterglow luminance is poor. Conversely, when e> 0.2, the afterglow luminance gradually decreases. It is preferably in the range of 0.0001 ≦ e ≦ 0.15, particularly preferably in the range of 0.002 ≦ e ≦ 0.10.

X represents the substitution rate when Mg is replaced with Zn. By replacing a part of Mg with Zn, a long afterglow time and high afterglow luminance can be realized. Mg is an essential component and the substitution with Zn is a partial substitution. However, in order to obtain better characteristics, the range of 0 ≦ x ≦ 0.5 is preferable, and the range of 0 ≦ x ≦ 0 is particularly preferable. .2.

Y indicates the substitution rate when Si is replaced with Ge, and long afterglow time and high afterglow luminance can be realized by partially replacing Si with Ge. Note that Si is an essential component and the substitution with Ge is a partial substitution. However, in order to obtain better characteristics, the range of 0 ≦ y ≦ 0.5 is preferable, and the range of 0 ≦ y ≦ 0 is particularly preferable. .2.

Further, when synthesizing the phosphorescent phosphor of the present invention, a phosphate such as boric acid or ammonium dihydrogen phosphate can be added as a flux. The optimum addition amount is in the range of 0.05 to 8% in mol%.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The raw material of the phosphorescent phosphor of the present invention comprises:
Oxides, carbonates, nitrates, hydroxides and the like can be used. After weighing these raw materials in a predetermined amount and sufficiently mixing them in a ball mill or the like, the raw materials are placed in an alumina crucible and placed in a reducing atmosphere such as hydrogen gas at 950 to 1500 ° C. for 1 to 12 hours.
Bake for hours. In some cases, the obtained fired product can be pulverized and refired, and this can be repeated two or more times. In that case, the baking in the middle may be in an oxidizing atmosphere, and may be in a reducing atmosphere in the final baking.

Known methods for synthesizing ceramic powders include a sol-gel method and a wet synthesis method (coprecipitation method). The phosphorescent phosphor of the present invention can also be synthesized by these methods, and can be produced by a general method of synthesizing a ceramic powder as long as it is within the composition range described in the claims of the present invention. It is not limited to the solid-phase reaction method described above. Hereinafter, the present invention will be described with reference to specific examples, but the present invention is not limited to these examples.

[0017]

【Example】

Example 1 SrCO ₃ 6.194 g MgO 0.761 g Al ₂ O ₃ 0.214 g SiO ₂ 2.395 g H ₃ BO ₃ 0.259 g Eu ₂ O ₃ 0.015 g Tm ₂ O ₃ 0.162 g The raw materials of the composition were thoroughly mixed, put in an alumina crucible, and mixed in a mixed gas stream of 97% N ₂ + 3% H ₂ at 1350.
C. for 3 hours at a chemical composition of 0.690 SrO.
310MgO · 0.0345Al ₂ O ₃ · 0.656Si
O ₂ · 0.0345B ₂ O ₃ · 0.00138Eu · 0.
A phosphorescent phosphor having 0138 Tm was obtained.

This phosphorescent phosphor is excited by the light of a fluorescent lamp,
FIG. 1 shows the emission spectrum one minute after the irradiation was stopped.
The measurement was performed using a spectrofluorometer. The emission peak wavelength was around 480 nm, and blue light emission was visually observed. FIG. 2 shows an excitation spectrum measured at an emission wavelength of 480 nm. From this spectrum, it can be seen that the excitation wavelength extends to the visible region and is easily excited by light such as sunlight or a fluorescent lamp.

The phosphorescent phosphors of Example 1 and Comparative Example A were excited with a fluorescent lamp at 200 lx for 20 minutes, and the change with time of the afterglow luminance immediately after the excitation was stopped is shown in FIG. The measurement was performed using a luminance meter (LS-100, Minolta Co., Ltd.). From this figure, it can be seen that the phosphorescent phosphor of Example 1 has higher luminance and longer afterglow time than Comparative Example A. Comparative Example A is a phosphorescent phosphor having an okermite composition.

Examples 2 to 2 exhibiting the same luminescent color as in Example 1
5 and Comparative Example A were produced in the same manner as in Example 1. Table 1 shows their compositions. The composition formula is 2 for each example.
The upper row is written in a form corresponding to the chemical composition formula, and the lower row is written in a form corresponding to the crystal structure. Each phosphorescent phosphor was excited at 200 lx for 20 minutes using a fluorescent lamp, and the afterglow luminance immediately after the excitation was stopped was measured with a luminance meter. The relative afterglow luminance shown in Table 1 is a relative value when the afterglow luminance of Comparative Example A is set to 100 in the afterglow luminance after 10 minutes from the stop of the excitation.

[0021]

[Table 1]

X-ray diffraction measurement was performed on Example 5 and Comparative Example A, and the obtained spectrum is shown in FIG. From this figure, it can be seen that the diffraction angle of Example 5 is clearly different from that of Comparative Example A, and has a different structure from Comparative Example A, that is, a melilite type structure.

In each of Examples and Comparative Examples A shown in Table 1, the composition formula represented by the crystal structure was represented by Sr ₂ Mg _1-n Al _2n S
i _2-n O ₇ , 0.1B ₂ O ₃ , 0.004 Eu, 0.040
FIG. 5 shows a generalized representation of Tm, and a plot of relative afterglow luminance versus n. This n represents the replacement ratio of the gehlenite composition to the akermanite composition. As is clear from this figure, the afterglow luminance of the akermanite (n = 0) composition indicates that the melilite composition (0 <n
The afterglow luminance of <1) is high, and is 3.75 times the maximum when n = 0.2, and is twice as high even when n = 0.4.

[0024]

Example 6 SrCO ₃ 4.889 g CaCO ₃ 1.105 g MgO 0.801 g Al ₂ O ₃ 0.225 g SiO ₂ 2.521 g H ₃ BO ₃ 0.273 g Eu ₂ O ₃ 0.016 g Tm ₂ O ₃₀ .170 g The raw materials having the above composition were sufficiently mixed, placed in an alumina crucible, and placed in a mixed gas stream of 97% N ₂ + 3% H ₂ for 1300 g.
C. for 3 hours at a chemical composition of 0.518SrO.
173CaO.0.310MgO.0.0345Al _{2
O 3 · 0.656SiO 2 · 0.0345B 2} O 3 · 0.0
A phosphorescent phosphor having 0138Eu · 0.0138Tm was obtained.

The phosphorescent phosphor is excited by light from a fluorescent lamp,
FIG. 6 shows the emission spectrum one minute after stopping the excitation.
The measurement was performed using a spectrofluorometer. The emission peak wavelength was around 490 nm, and blue-green emission was visually observed.

Examples 7 to 14 were produced in the same manner as in Example 6. Table 2 shows their compositions. Each phosphorescent phosphor was excited at 200 lx for 20 minutes using a fluorescent lamp, and the afterglow luminance immediately after the excitation was stopped was measured with a luminance meter.
The relative afterglow luminance shown in the table is a relative value in which the afterglow luminance of Comparative Example B is set to 100 in the afterglow luminance 10 minutes after the stop of the excitation.

[0027]

[Table 2]

The emission spectra measured for the phosphorescent phosphors of Examples 10, 12, and 14 are shown in FIGS.
Shown in The measurement was excited by a fluorescent lamp, and the emission spectrum one minute after stopping the excitation was measured by a spectrofluorometer. In FIG. 7, the emission peak wavelength was at 505 nm, and green light emission was visually observed. In FIG. 8, the emission peak wavelength was at 520 nm, and yellow-green emission was visually observed. In FIG. 9, the emission peak wavelength was at 468 nm, and dark blue emission was visually observed. Thus, by replacing Sr with Ca and Ba, it is possible to realize various light emission from blue to yellow-green.

[0029]

The present invention is configured as described above and has the following effects. The phosphorescent phosphor according to the present invention realizes a long afterglow time and a high persistence luminance as compared with the conventional silicate phosphorescent phosphor, and has various emission colors from blue to yellow-green, It can be provided for a wide range of applications.

[Brief description of the drawings]

FIG. 1 is an emission spectrum one minute after stopping light excitation in Example 1.

FIG. 2 is an excitation spectrum at an emission wavelength of 480 nm in Example 1.

FIG. 3 is a graph showing a change over time in afterglow luminance of Example 1 and Comparative Example A.

FIG. 4 is an X-ray diffraction chart of Example 5 and Comparative Example A.

FIG. 5: Sr ₂ Mg _1-n Al _2n Si _2-n O ₇ · 0.1B ₂ O ₃
It is the graph which plotted the relative afterglow luminance 10 minutes after stopping excitation with respect to n in 0.004Eu0.040Tm.

FIG. 6 is an emission spectrum one minute after stopping light excitation in Example 6.

FIG. 7 is an emission spectrum one minute after stopping light excitation in Example 10.

FIG. 8 is an emission spectrum one minute after stopping light excitation in Example 12.

FIG. 9 is an emission spectrum one minute after stopping light excitation in Example 14.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yasuo Ochi 1-15-30 Koyama, Sagamihara-shi, Kanagawa F-term in Ohara Co., Ltd. 4H001 CA04 XA08 XA12 XA13 XA14 XA20 XA30 XA32 XA38 XA56 YA21 YA25 YA39 YA39 YA40 YA41 YA49 YA50 YA57 YA58 YA59 YA60 YA62 YA63 YA64 YA65 YA66 YA67 YA68 YA69 YA70 YA71 YA83

Claims (1)

[Claims] 1. A activated with divalent europium, the chemical composition formula aRO · (1-a) ( Mg 1-x Zn x) O · bAl
₂ O ₃ · c (Si _{1 -y} Ge _y ) O ₂ · dEu · eM (however,
R is at least one selected from the group consisting of Ba, Sr and Ca, M is a coactivator, and Nb, Zr, Bi, M
n, Sn, In, La, Ce, Pr, Nd, Sm, G
d, Tb, Dy, Ho, Er, Tm, Yb, Lu, S
at least one member selected from the group consisting of c and Y)
Where a, b, c, d, e, x, and y are 0.4 ≦ a ≦ 0.9, 0.00001 ≦ b <0.30, 0.25 ≦ c ≦ 1.5, 0, respectively. 0.0001 ≦ d ≦ 0.2, 0.00001 ≦ e ≦ 0.2, 0 ≦ x <1.0, 0 ≦ y <1.0.