JPS6011579A - Phosphor - Google Patents

Abstract

PURPOSE:To provide a phosphor having improved luminance and after-glow property, prepd. by adding an alkali element to a europium-activated LaF3.AX2 compd. CONSTITUTION:The phosphor is shown by the formula (where A is an alkaline earth metal element consisting of at least one of Ba, Sr and Ca; X is an alkali element consisting of at least one of F, Cl and Br: n/m is 1X10<-3>-7X10<-1>; a is 1X10<-4>-3X10<-1>; b is 0-2X10<-2>). For higher emission efficiency, the concn. (a) of Eu which is used as activator, should be 1X10<-4>-3X10<-1>. Within this range, the efficiency of emission remains essentially constant without occurrence of concn. quenching. The ratio n/m, which represents the composition of a matrix should be 1X10<-3>-7X10<-1>, for a high luminance as well as momentary emission by radiation are obtainable within this range. The phosphor is obtained, e.g., by burning in a crucible a mixt. of lanthanum fluoride, barium fluoride and barium bromide with europium oxide and chloride or bromide of an alkali element.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) This invention relates to a fluorohalogen compound phosphor.

[Technical background of the invention and its problems] As a conventional means for recording and reproducing radiation images, there is a photographic method using a silver halide film coated with a phosphor. On the other hand, the problem of exposure dose in medical radiological diagnosis is particularly serious when the human body is targeted, and reduction of the dose is strongly desired. Furthermore, from the standpoint of diagnosis, it is desirable to obtain as much and more accurate information as possible from the images recorded in the captured images. Since conventional photography methods are insufficient to meet these demands,
Radiographic image conversion systems such as those disclosed in US Pat. No. 3,859,527 and others are viewed as promising.

This system uses radiation that has passed through an object to accumulate a latent image of the object on a radiation image conversion plate having a stimulable or thermoluminescent phosphor, and then regenerates the image. Therefore, in order to put this system into practical use, a stimulable or thermoluminescent phosphor that has a high radiation absorption rate and can release stored energy with high efficiency is required to reduce the exposure dose. Furthermore, due to the strong desire to shorten diagnosis time, a phosphor with less photostimulated afterglow during readout is required.

The inventors of the present invention have made various studies focusing on the fact that europium-activated LaF, .AX, compounds have high luminous efficiency, as disclosed in JP-A-53-112291. As a result, the use of alkaline earth fluorides and halides, which has been attempted not only to emit light during X-ray irradiation (referred to as instantaneous luminescence), but also to emit light due to photoexcitation of stored energy (referred to as stimulated luminescence), has been demonstrated. It was discovered that it has properties superior to that of light.

That is, the europium-activated LaF3.AX compound satisfies the two requirements of high X-ray absorption and high stimulated luminescence efficiency. However, there is a problem with the third requirement, that is, afterglow property. The decay time of the stimulated luminescence of conventional europium-activated alkaline earth element/loginide phosphors is several microseconds, whereas the decay time of europium-activated LaF is 1° AX1! The compound exhibits a decay time of several hundred microseconds, preventing its practical application. Therefore, it is necessary to improve the afterglow characteristics while maintaining high efficiency.

The present inventors have discovered that by adding a trace amount of alkali salt to a europium-activated LaF, .AX2 compound, the afterglow characteristics of stimulated luminescence can be significantly improved, leading to the present invention.

It has been reported in Japanese Patent Publications No. 18470-18470 and No. 7108-7108 that the afterglow characteristics of instantaneous X-ray emission are improved in compounds of europium-activated alkaline earth fluorohalide phosphors and alkali salts. has been disclosed.

However, all of these are related to the improvement of delayed luminescence, which is a problem in intensifying screens and lasts for several tens of milliseconds immediately after X-ray irradiation, and the present invention, which improves the afterglow characteristic of several microseconds in stimulated luminescence, This effect is essentially different.

[Object of the present invention]

The present invention provides a novel phosphor with improved photostimulated afterglow characteristics by incorporating an alkali element into the europium-activated LaFB/AX compound.

Summary of the invention] The general formula of the phosphor according to the present invention is as follows.

nLaF3-mAX, : aEu, bD However,
X is an alkaline earth element consisting of at least one of Ba, Sr, and Ca; X is a halogen element consisting of at least one of F, C/, and Br; D is an alkali element consisting of at least one of Rb; So, n/frI is 1xxo”
≦n/m S 7X1 (r”+ a is lXl0”≦a≦
3×1σS, b is a value satisfying o<b≦2×12.

As shown in FIG. 1, the concentration a of Eu, which is an activator, is preferably 1x16'≦a≦3xl (r') from the viewpoint of luminous efficiency.

Within this range, concentration quenching does not occur and the luminous efficiency remains almost constant. On the other hand, the matrix composition ratio n/fn is 1×163≦
It is desirable that n/in<7xlO'. Within this range, the photostimulated luminance is very strong, similar to instantaneous light emission due to radiation.

For example, in Figure 2, the Bu concentration is 5 x 1 per mol of parent material.
5 x 1 o' moles for 6' moles, 16 alkali elements
When the number of moles in the matrix is fixed at 3 mol and the matrix is a compound series of LaF3 and BaFBr, the number of moles n in the matrix of LaF3 and BaF
It is the photostimulated luminance after X-ray irradiation with respect to the change in the number of moles of Br in the matrix (m). Curve 1 uses potassium as the alkali metal, and curve 2 uses rubidium. From Figure 2, the mother composition ratio n/fn is xxxo”≦n/fn≦7
A range of 61 is desirable. This tendency does not change at all if the matrix composition is defined by other elements according to the present invention. For example, when the matrix is a compound series of LaFs and 5rFBr, the matrix composition ratio n/m is lX1 from FIG.
It is desirable that 0""≦n/fr1≦7xto'. Thus, curve 1 represents addition and curve 2 represents addition. Similarly, the mother body is LaFH and CaFCI! From Figure 4, the parent composition ratio n7fn for the compound series with is 1×1σ3≦n/
It is desirable that fn≦7×161. Here curve 1 is added to 1
Curve 2 is Rh addition.

In addition, the content of alkaline elements is o<b≦2X
1o'' is desirable. By containing the above-mentioned alkali elements, the effect of improving afterglow characteristics is reduced.

When it exceeds 2×IC, the photostimulated luminance decreases significantly. FIG. 5 shows 0,04LaPs・Q, which is one of the phosphors according to the present invention.
, 95BaFBr: 0.0005Eu, after irradiating the bD phosphor with X-rays of 80 KVI), it was left in the dark for about 1 hour, and a red light emitting diode (wavelength 660 nm) was irradiated.
FIG. 2 is a diagram showing the relationship between the stimulable luminescence intensity and the alkali element content using light from the excitation source. Here, D is potassium (curve 1) and rubidium (curve 2). In Fig. 5, the vertical axis is b=0, that is, 0.04LaFs ・096BaFBr: O, in which no alkali element was intentionally added.
It is a relative intensity with the stimulable luminescence intensity of the 0O05Eu phosphor as 100. As is clear from Fig. 5, within the range of b≦2×1, the stimulable luminescence intensity due to the addition of an alkali element is
No significant decline is seen. This tendency is exactly the same if the matrix composition is defined as one composed of other elements according to the present invention. For example, as shown in Figure 6, 0.04LaF
s-0,965rBaF: 0.0005Eu,b
K (curve 1), and 0.04LaPs @ 0.96
CaFC1! : O,0O05Bu, bRb (curve 2), if b≦2×162,
There is little decrease in photostimulated brightness.

On the other hand, the effect of improving afterglow characteristics is clear from FIG. FIG. 7 shows 0,04LaF, which is one of the phosphors according to the present invention.
a・0.96BaFBr: 0.0001u, 0,04LaFs・0.96 BaF, which is one of the bK phosphors
Br: 0.0001u, 80[Vp for bK phosphor
After irradiating with X-rays, leave it in the dark for about an hour.
FIG. 3 is a diagram showing the afterglow characteristics of stimulated luminescence using a red light emitting diode with a pulse width of 10 microseconds as a pulsed light source. 7th
In the figure, the contents are b=0 (curve 1), b=x6''
c curve 2), b = 16' (curve 3), b = 10 (curve 4), and the vertical axis represents the photostimulated luminance immediately after pulse excitation at 10
The relative intensity is set to 0, and the horizontal axis represents the elapsed time from immediately after pulse excitation. As is clear from FIG. 7, the afterglow characteristics are significantly improved by adding potassium. In practice, the one-tenth decay time is required to be about 10-odd microseconds or less, so the amount of potassium added may be 10 or more. FIG. 8 shows the relationship between the amounts of potassium (curve 1) and rubidium (curve 2) added and the 1/10 decay time. In this way, the effect of improving afterglow characteristics is the same even when Rb is added. Figure 9 shows
0.04LaP, 0.968rFBr: O,00
05Eu,bD is a diagram showing the relationship between the added amount of K (curve 1) and Rh (curve 2) and the 1/10 decay time. Also, Figure 10 shows 0.04LaFs・0.96Ca
FCl: 0.0005Eu, K in bD
(Curve 1) and Rb (Curve 2) are diagrams showing the relationship between load and 1/10 decay time. In this way, improvements in properties by introducing alkali and elements can be obtained in exactly the same way if the host composition is defined as one containing other elements according to the present invention. Therefore, taking into consideration the effect of improving the photostimulated brightness and afterglow characteristics, it is desirable that the alkali element content is o<b≦25t. More preferred is 1 cutting O''4≦b≦2 cutting 01.

As is clear from the above, europium-activated nLaF,·mAX contains an alkali element as an additive.

It is recognized that the afterglow property of the phosphor is significantly improved compared to the case where the phosphor does not contain the phosphor.

The phosphor according to the present invention is formed as follows.

For example, the phosphor can be obtained by mixing lanthanum fluoride, barium fluoride, barium bromide, europium oxide, chloride or bromide of an alkali element, etc. by physical means, filling a crucible, and then firing the mixture. I can do it.

[Embodiments of the invention]

The present invention will be explained below using Example I.

Example 1 Lanthanum fluoride 3.3 F, barium fluoride 35.8 F
, barium bromide 60.7f, europium oxide 0.07
5L of potassium bromide 0.0055' was mixed by physical means and fired in a reducing atmosphere at 850°C for 2 hours on a quartz Ruho to form 0D4LaFs 0.96 BaFBr.
: 0.0005Bu, 0.0001 to obtain a phosphor.

Example 2 The raw material of Example 1 was calcined in the same manner as potassium bromide at 0.055', resulting in 0.04LaFa*0.9.
6 BaFBr:0D005EL! , 0.001
to obtain phosphor.

Example 3 The raw material of Example 1 was calcined in the same manner as potassium bromide as 052, resulting in 0.04LaF3 @ 0.96 B
aFBr: 0.0005Ell, 0.01 with phosphor.

After the phosphor obtained by the above manufacturing method was irradiated with 8QKVp X-rays, it was left in the dark for about 1 hour, and the decay time of 1/10 of the stimulated luminescence pulse-excited with a red light emitting diode is shown in Table 1. . The conventional example is 0.04L, which was obtained by the same manufacturing method and does not contain potassium bromide.
aFs ・0.96 BaFBr: 0.0005E
This is the 1/10 decay time of the u phosphor measured under the same conditions.

Table 1 Example 4 Lanthanum fluoride 052. Barium fluoride 36.9 y, barium bromide 625 europium oxide 0.07 y! V, rubidium bromide 0.007 F mixed by physical means,
Calcinate in a quartz crucible at 850°C for 2 hours in a reducing atmosphere to obtain 0f106LaF3 ・O'+94BaFBr:
A 0.0005Eu, O,0OOIRb phosphor is obtained.

Example 5 0.07 fI of rubidium bromide in the raw material of Example 4
The same firing was performed as 0.006LaFs・0.
994BaFBr: O, 0O05Eu, 0.0OIRb
Obtain phosphor.

Example 6 Similar firing was performed using the raw material of Example 4 with rubidium bromide at 0.79, and 0.006LaF, .0994
BaFBr:0000! Ju, 0.01 liter of phosphor is obtained.

After irradiating the phosphor obtained by the above manufacturing method with X-rays of 80 KVp, it was left in the dark for about 1 hour, and the decay time of 1/10 of the stimulated luminescence pulse-excited with a red light emitting diode is shown in Table 2. . The conventional example is 0,006L obtained by the same manufacturing method except that it does not contain rubidium bromide.
aFs ・0.994BaFBr: 0.0005E
This is the 1/10 decay time of the u phosphor measured under the same conditions.

Table 2 Example 7 Lanthanum fluoride 4.1F, barium fluoride 43B9. Barium chloride 52. OF, europium oxide 0.09y, potassium chloride 0.004! F was mixed by physical means and fired in a quartz crucible at 850°C for about 2 hours in a reducing atmosphere to form 004LaFs .O! :J6BaFCl! : 0
．． A phosphor is obtained at 0.0005Eu and 0.0001.

Example 8 The same firing was performed using the raw material of Example 7 except that potassium chloride was changed to 0.04P to produce 0.04LaFa ・0.96
BaPC/:0.0O05Eu, O,0OIK phosphor is obtained.

Example 9 The same firing was performed using the raw material of Example 7 using potassium chloride as 049 to obtain 0.04LaFs・0.96BaF'
C/: 0.0005Eu, 0.01 to obtain a phosphor.

Table 3 shows the 1/10 decay time obtained under the measurement conditions described in the previous section. The conventional examples are Q and Q4LaF obtained by the same manufacturing method except that they do not contain potassium chloride.

-096BaFC/: 1/10 decay time of 0.0005Eu phosphor measured under the same conditions.

Example 10 Lanthanum fluoride 0419. Barium fluoride 45.4 F,
Barium chloride 5399. europium oxide 0.09
F, 0.006 y of rubibidyram chloride was mixed by physical means and fired in a quartz rutsuho at 850°C for about 2 hours in a reducing atmosphere to produce 0.006LaFs ・0.994B.
aFC/: O,0O05Eu, 0.0001R
Obtain h phosphor.

Example 11 In the raw material of Example 10, rubidium chloride was added to 0.06
Similar firing was performed as fJ to give 0.006LaF, -0
994BaFC/: 0.0005Eu, 0.001Rb
Obtain phosphor.

Example 12 The same firing was performed using the raw material of Example 10 with rubidium chloride being changed to 0.67 to produce 0.006LaFs 0.099
4BaFCe: O, 0O05Eu, 0.01Rb phosphor obtained.

Table 4 shows the 1/10 decay time obtained under the measurement conditions described in the previous section. The conventional example is 0,006LaFs-0,9 obtained by the same manufacturing method except that it does not contain rubidium chloride.
94BaFCl: O, 0O05Eu, 0.0IRb
This is the 1/10 decay time of the phosphor measured under the same conditions.

Lanthanum fluoride 4.2 F, strontium fluoride 32.
2P.

Stoconitium bromide 63B? , europium oxide 01)
47, 0.006 F of potassium bromide was mixed by physical means, and calcined in a quartz crucible at 850°C for 2 hours in a reducing atmosphere to yield 0.04 LaF, 0.018 rFBr:0.
．． 0005Eu, 0OO01K phosphors are obtained.

Example 14 Potassium bromide was added to the raw material t of Example 13.
The same firing was performed as 0.04LaFs・0.
96SrFBr: 0.0005Bu, 0.001
to obtain phosphor.

Example 15 The raw material of Example 13 was calcined in the same manner as potassium bromide at 0.67, resulting in 0.04LaFs-0,968.
rFBr: 0.0005Eu, 0. Obtain OIK phosphor.

After irradiating the phosphor obtained by the above manufacturing method with X-rays of 80 KVp, it was left in the dark for about 1 hour, and the decay time of 1/10 of the stimulated luminescence pulse-excited with a red light emitting diode is shown in Table 5. . The conventional example is 0,04LaFs obtained by the same manufacturing method except that it does not contain potassium bromide.
・0.96S rFBr: 0.0005Eu This is a 1/10 decay time measured under the same conditions.

Table 5 Example 16 7.9 L of lanthanum fluoride, 38 L of calcium fluoride, 54 g of calcium chloride, 0.095' of europium oxide, and 0.019 of potassium bromide were mixed by physical means, and the mixture was heated at 850°C in a reducing atmosphere for 2 hours. Time quartz. Fired at the brim, 0.
04LaFs ・0.96CaFCl! : 0.00
The phosphor is obtained at 0.05Eur 0.0001.

Example 17 The same calcination was performed using the raw material of Example 16 with 0.1 g of potassium bromide, resulting in 0.04LaF3・0.96C.
aFCl! :0f1005Fiu, 0.001 to obtain fluorophore.

Example 18 The raw material of Example 16 was calcined in the same manner using potassium bromide as a general solvent, resulting in 0.04LaFs' 0.96C.
Obtain the fluorophore at aFC/: 0.0005Eu, 0.01.

The phosphor obtained by the above manufacturing method was irradiated with X-rays of 8 Qicvp and then left in the dark for about 1 hour, and the decay time of 1/10 of the stimulated luminescence pulse-excited with a red light emitting diode is shown in Table 6. . In the conventional example, the tl of potassium bromide-free was obtained by the same manufacturing method (MJ4LaF
s ・096CaFCl! :01:) This is the 1/10 decay time of the O05Bu phosphor measured under the same conditions.

(Top, L1 Yuku) Table 6 [Effects of the Invention] As described above, the europium-activated LaF, AX, and phosphors containing trace amounts of alkali elements according to the present invention have high photostimulated luminance and do not leave any stains. It is a phosphor with improved optical properties, and is very useful in application to storage type radiation image conversion plates.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the Eu concentration a and the photostimulated brightness of the phosphor according to the present invention, and FIGS. 2 to 4 are diagrams showing the relationship between the matrix composition ratio ψ and the Figures 5 and 6 are diagrams showing the relationship between the amount of alkali metal added and the stimulated luminance of the phosphor according to the present invention, and Figure 7 is a diagram showing the relationship between the stimulated luminance and the phosphor according to the present invention Figures 8 to 10, which show the afterglow characteristics of stimulated luminescence of a luminescent material, are diagrams showing the effect of improving the afterglow characteristic of stimulated luminescence by adding an alkali metal to a phosphor according to the present invention. Representative Patent Attorney Noriyuki Chika (and 1 other person) 9 No. l Mouth α Fig. 2 (71/hrL) Fig. 81 Fig. 4 Fig. 5 Fig. 7 JP-A-11579 (7) A Natsume g Microken

Claims (1)

[Claims] A phosphor having the general formula nLaF3.mAX2: aEu, bD. However, A is an alkaline earth element consisting of at least one of Ba, Sr, and Ca, and X is F, cl! , a halogen element consisting of at least one type of Br, D is an alkali element consisting of at least one type of Rb, n7m is 1xlO"-n
7m < 7×161. a is I X 10-'≦a<
3X16″1.b is 0<b<2XIO.