JPS5938280B2 - fluorescent material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to terbium-activated rare earth oxysulfide phosphors, and particularly to improvements in phosphors that emit light in the blue to green region.

As is well known, phosphors based on rare earth oxysulfides are used for X-ray fluorescent surfaces such as intensifying screens, fluorescent plates, and X-ray fluorescent multiplier tubes due to their high luminous efficiency and high X-ray absorption. It's starting to feel like this.

These X-ray fluorescent surfaces are required to have a large amount of X-ray absorption, high luminous efficiency, weak afterglow components, and good resolution. However, the intensifying screen has Y202S:Tb,
(Y,,Gd)202S:Tb,,Gd202S:Tb
) La202S:Tb and other phosphors have been put into practical use, of which Y202S:Tb and (Y,Gd)202S■Tb are mainly used for regular films sensitive to the blue region, and Gd202S:Tb) La202S:Tb is It has been put into practical use for orthofilms with sensitivity in the blue to green region.

These rare-earth element oxysulfide phosphors have higher luminous efficiency than CAWO4 phosphors, which have been used as phosphors for conventional intensifying screens, and have the same or higher absorption of X-rays, making them more susceptible to radiation exposure. This is very advantageous in terms of mitigation.
However, this rare earth element oxysulfide phosphor has a strong afterglow component compared to the conventional CAWO4 phosphor, and an improvement has been desired. On the other hand, X-ray fluorescence multiplier tubes are particularly required to have improved resolution. This resolution is improved by increasing contrast. The present invention relates to such an oxysulfide phosphor, which is particularly aimed at weakening afterglow components, improving contrast, or improving luminous efficiency. i.e. terbium-activated gadolinium,
This was achieved by incorporating a trace amount of cerium into a phosphor based on oxysulfide consisting of at least one of yttrium, lanthanum, and lutetium, and has the general formula (1-x-y) M202S-XTb202S-yC.
It is a phosphor expressed as e2O2S.

However, in the above formula, M is a rare earth element consisting of at least one of Gd, Y, La, and Lu, 5×10-5≦x≦1×1
0-1, 5×10-7≦y≦1×10-3. The phosphor of the present invention will be described in detail below with reference to FIGS. 1 to 3. First, general formula (1-x-y) M202S-XT
b202S-yCe202S where M is yttrium and gadolinium, x=0.001, y=1×10-5, that is (Yo, 5・Gd0.5)202S-O
, 001Tb202S・1×10-5Ce202S, and for comparison, when y=o, that is, (YO
．． 5. GdO. 5) 202S- 0.001Tb202
The afterglow characteristics of the phosphor S are shown in FIG.

In Figure 1, the vertical axis shows the afterglow intensity (arbitrary unit), where the luminescence intensity after 0.5 seconds after the phosphor is stimulated with X-rays is 100, and the horizontal axis shows the residual light intensity. Reduces the decay time of light. According to FIG. 1, it can be seen that the phosphor of the present invention shown by curve 1 has significantly superior afterglow characteristics as compared to the comparative phosphor shown by curve 2.

Furthermore, in the same figure, in the above general formula, when M is gadolinium, x=0.1, and y=1×10-4, that is, 0.9Gd202S・0.1Tb202S・0.
0001Ce202S phosphor and y= for comparison
If 0, Rei Sunawa 0.9Gd202S- 0.1T
The afterglow characteristics of the b202S phosphor are also shown.

According to the figure, it is clear that the phosphor of the present invention shown by curve 3 has superior residual properties compared to the comparative phosphor shown by curve 4. Furthermore, FIG. 2 shows the afterglow characteristics of the phosphor of the present invention and the comparative phosphor as well as FIG.
=5×10-6, i.e. Y2O2S-0.0
004Tb202S/5×10-6Ce202S, the phosphor of the present invention, curve 6 is the comparative phosphor, Y2O2S.
-0.0004Tb202S phosphor.

In addition, the curve T in the same figure shows that in the above general formula, M is La. x=
0.007, y=0.001, that is, the phosphor of the present invention, curve 8 is the comparative phosphor, that is, 0.993La.
202S - Shows a 0.007Tb202S phosphor.

According to FIG. 2, the phosphor of the present invention with curve 5 and curve T is curve 6.
, curve 8 shows that the afterglow properties are superior to those of the comparative phosphor shown by curve 8.

As described above, it is clear from FIGS. 1 and 2 that the addition of cerium improves the afterglow characteristics. The effective range of (y) in the above general formula will be explained using a terbium-activated yttrium and gadolinium oxysulfide phosphor as an example. *The amount of cerium added is 5×10-7<y<1×10-7 under X-ray stimulation due to afterglow characteristics.
The optimum value is y=3×10−6. That is, if even a small amount of cerium is contained, an effect on afterglow properties can be observed, but when y=3×10 -6 the effect of reducing afterglow components is remarkable. In addition, y>1×10-3
If this happens, the light emitting characteristics will be significantly degraded, as will be described later, and it will not be put to practical use. Next, using a terbium-activated yttrium gadolinium oxysulfide phosphor as an example of the phosphor of the present invention, we will explain how it affects the luminescence characteristics when it contains 1 mol of cerium, with reference to Figure 3. explain.

In FIG. 3, the vertical axis shows the brightness (relative value) when the phosphor emits light by X-ray stimulation or electron beam stimulation, and the horizontal axis shows the amount of cerium added in the phosphor. According to FIG. 3, in the above general formula, the luminous efficiency is significantly improved when y is 5×10 −5 .

For example, with X-ray stimulation, a maximum brightness improvement of 30% was obtained compared to y=0, that is, a material not containing cerium, and with electron beam stimulation, a maximum brightness improvement of 5% relative to a material not containing cerium was obtained. Also, the brightness with X-ray stimulation is 5×1
When the value exceeds 0-5, it decreases, and this is thought to be due to the addition of cerium, which causes a yellow body glaze to form on the phosphor itself. However, according to the inventor's experiments, V is 1×10
It has been confirmed that around -3 there is no practical problem as an X-ray fluorescent surface. Next, the reflection spectra and emission spectrum distributions of various terbium-activated rare earth oxysulfide phosphors of the present invention will be explained with reference to FIGS. 4 and 5. Note that FIG. 4 1 and FIG. 5 1 show the reflection spectrum distribution, and the vertical axis shows the reflectance (%) and the horizontal phase de-wavelength (Nm). FIG. 4 2 and FIG. 5 2 show the emission spectrum distribution, with the vertical axis showing the emission intensity (arbitrary unit) and the horizontal axis showing the wavelength. Furthermore, the wavelengths shown in Fig. 4 1 and Fig. 5 1 are the 4th wavelength.
The scale is omitted because it corresponds to the wavelength shown in FIGS. 2 and 5. According to FIG. 4 1 and FIG. 5 1, various terbium-activated rare earth oxysulfide phosphors have an absorption peak at 450 nm due to the addition of cerium.
It has an absorption band in the 540 nm region. This means that the body glass is colored by the phosphor, which has the effect of preventing scattering of the light emitted from the phosphor and improving contrast when used as a screen. Furthermore, although FIG. 4 2 and FIG. 5 2 show the emission spectrum distribution of various conventional rare earth oxysulfide phosphors upon X-ray stimulation, the cerium-doped homogeneous rare earth oxysulfide phosphor according to the present invention Since the emission line of the phosphor is also located in the same position, it has an emission peak in blue or green and is suitable for intensifying screens and X-ray fluorescence multiplier tubes. In the following, we will discuss the case where the cerium-doped phosphor of terbium-activated yttrium gadolinium oxysulfide according to the present invention is used in an intensifying screen. ×10-5〈Tb〈1×1
0-? 5X10-4〈Tb〈1×
10-1 is appropriate. However, 5×10−4〈Tb≦1
×10-2, it can be practically used for regular films and ortho films. In addition, when performing normal X-ray diagnosis, X-rays are irradiated to make an intensifying screen emit light to expose a film and obtain an X-ray photograph, but conventional terbium-activated yttrium or gadolinium oxysulfide phosphors are used. The intensifying screen has higher sensitivity than the intensifying screen using the CawO4 phosphor, but has a longer afterglow and has poor graininess that affects the resolution. Photosensitive paper has high sensitivity and short afterglow. In addition, since the body glass of the phosphor of the present invention is colored by the addition of cerium, it absorbs the scattering of light within the phosphor layer and produces high-quality, high-resolution X-ray photographs with less blur. is obtained. Furthermore, the phosphor of the present invention can be easily manufactured by a conventional method. For example, a rare earth oxide consisting of element M and terbium and cerium in the general formula above, or other compounds that can be converted into oxides by heating and calcination, such as carbonates, oxalates, and nitrates, and sulfur are mixed. However, it can be easily obtained by finely pulverizing, uniformly mixing the respective raw materials, and firing. At this time, a suitable fluxing agent such as sodium carbonate may be added. Since cerium and terbium, which are used as raw material components, are in extremely small amounts compared to other components, some consideration must be given to the raw material mixing process during production. That is, even if exactly the same raw materials are used, the characteristics of the resulting product will differ depending on how uniformly the raw materials are mixed and the degree of uniformity. Therefore, rather than simply mixing raw material powders by mechanical means, better results can be obtained by dissolving the raw materials in an appropriate liquid and adding an appropriate precipitating agent to each rare earth element in the solution to cause coprecipitation. can get. For example, if nitric acid is used as the liquid for dissolving the raw material or oxalic acid solution is used as the precipitant and these solutions are mixed, the rare earth element can be co-precipitated as oxalate. As described above, according to the present invention, a phosphor having an extremely weak afterglow component can be obtained by incorporating an appropriate amount of cerium into an oxysulfide phosphor made of a specific rare earth element. Cerium contained in the phosphor raw material hardly decreases even after the firing process, and remains quantitatively present in the phosphor as it is. The above-mentioned phosphor has been specifically described for use in intensifying screens, but as will be clear from the examples described later, it is also suitable for use in X-ray fluorescent multiplier tubes, color cathode ray tubes, mercury lamps, and the like. Examples of the present invention will be described in detail below. Example 1 Yttrium oxide 22.5y and gadolinium oxide 36
．． 2y is dissolved in 80 ml of concentrated nitric acid, and the nitric acid solution is made up to 300 ml with pure water.

Next, prepare a terbium nitrate solution containing 1 x 10-2 moles of terbium in 11, add 20 ml of this solution to further prepare a cerium nitrate solution containing 5 x 10-4 m01 of cerium in 11, and add 20 ml of this solution to the above solution. Added to nitric acid solution containing yttrium and gadolinium,
This mixture is stirred well and heated to 60°C. On the other hand, an oxalic acid aqueous solution prepared by dissolving oxalic acid 807 in 200 ml of pure water is heated to 80°C, and added to the nitric acid solution heated to 60°C while stirring, and after the addition is completed, stirring is continued for another 10 minutes. In this way, yttrium, gadolinium, terbium, and cerium oxalates are produced and coprecipitated in the mixed solution. Next, the solution containing such a precipitate is allowed to cool, and then washed five times with pure water by decantation, and the precipitate is suction filtered. This precipitate was heated to 150°C for 10
Dry for 1 hour, then heat decompose at 1000℃ for 1 hour,
Oxalate is an oxide. 50 y of the oxide thus obtained, 12.5 y of sulfur and 12.5 y of sodium carbonate.
After 5V and 7V of potassium phosphate were added, mixed well, and fired in a closed crucible at 1200°C for 3 hours, the sintered body was ground in a ball mill, thoroughly washed with water, and then diluted with dilute hydrochloric acid three more times. After washing and further washing off hydrochloric acid with pure water, it is dried at 120°C. The general formula of the phosphor thus obtained can be expressed as follows, and the afterglow of this phosphor is extremely lower than that of a comparative product that does not contain cerium.

(Curve 1 in Figure 1) Furthermore, the brightness was improved by 25% when stimulated by X-rays and by 10% when stimulated by electron beams compared to a comparative product that did not contain cerium. When this phosphor is used in an intensifying screen, it must contain cerium) [with a contrast of 3.
0% improvement, and furthermore, the sensitivity of the film due to afterglow when changing the film also disappeared. Example 2 Appropriate amounts of yttrium oxide, terbium, and cerium were mixed and produced in the same manner as in Example 1 to obtain a phosphor having the general formula.

This phosphor has a much weaker afterglow component than a comparative product that does not contain cerium (curve 5 in Figure 2). In addition, the brightness was improved by 20% when stimulated by X-rays and by 10% when stimulated by electron beams compared to a comparative product that does not contain cerium. When this phosphor is used in an intensifying screen, compared to one that does not contain cerium,
Trust improved by 5%. Example 3 A phosphor was produced in the same manner as in Example 1 by mixing appropriate amounts of gadolinium oxide, terbium, and cerium, and the general formula was 0.9Gd202S-0.1Tb202S.0.0
A phosphor designated as 001Ce202S was obtained.

This phosphor has a much weaker afterglow component than a comparative product that does not contain cerium (curve 3 in Figure 1). Furthermore, when this phosphor is applied to an intensifying screen and an X-ray fluorescence multiplier tube, the former has a contrast of 25% compared to one that does not contain cerium.
The latter showed a 40% improvement in contrast. Example 4 A phosphor was manufactured in the same manner as in Example 1 by mixing appropriate amounts of lanthanum oxide, terbium, and cerium to obtain a phosphor having the general formula.

This phosphor has a much weaker afterglow component than a comparative product that does not contain cerium (curve T in Figure 2). When this phosphor was used in a phosphor plate, the contrast was improved by 50% compared to a comparative product that did not contain cerium. Therefore, X-rays
-The image is now much easier to see. Example 5 A phosphor was produced in the same manner as in Example 1 by mixing appropriate amounts of gadolinium oxide, lanthanum oxide, and terbium cerium.
A phosphor with a general formula was obtained.

This phosphor had a much weaker afterglow component than a comparative product containing no cerium, and was almost the same as curve 1 in FIG. Furthermore, when this phosphor was used in an intensifying screen, the contrast was improved by 15% compared to a screen that did not contain cerium. Example 6 A phosphor was manufactured in the same manner as in Example 1 by mixing appropriate amounts of yttrium oxide, lutetium oxide, terbium, and cerium to obtain a phosphor having the general formula.

The brightness of this phosphor was improved by 25% when stimulated with X-rays and by 10% when stimulated with electron beams compared to a comparative product that did not contain cerium.
Furthermore, when this phosphor was used in an intensifying screen, the contrast was improved by 5% compared to a screen that did not contain cerium. Example 7 Appropriate amounts of gadolinium oxide, lanthanum oxide, terbium, and cerium were mixed and a phosphor was manufactured in the same manner as in Example 1 to obtain a phosphor having the general formula.

This phosphor had a much weaker afterglow component than a comparative product that did not contain cerium, and was almost the same as curve T in FIG. In addition, when this fluorophore is used in a fluorescent plate and an X-ray fluorescent multiplier tube, the contrast is 10% in the case of a fluorescent plate and 10% in the case of an X-ray fluorescent multiplier tube compared to one that does not contain cerium. Improved by 20%. Example 8 A phosphor was produced in the same manner as in Example 1 by mixing appropriate amounts of gadolinium oxide, lutetium oxide, terbium, and cerium to obtain a phosphor having the general formula.

This phosphor had a much weaker afterglow component than a comparative product containing no cerium, and was almost the same as curve 5 in FIG. Also, the brightness is X compared to a comparative product that does not contain cerium.
It improved by 10% with line stimulation and by 5% with electron beam stimulation. Furthermore, when this phosphor was used in an X-ray fluorophore multiplier tube, the contrast was improved by 10% compared to a phosphor containing no cerium. Example 9 Yttrium oxide, gadolinium oxide, lanthanum oxide,
A phosphor was produced in the same manner as in Example 1 by mixing appropriate amounts of terbium and cerium to obtain a phosphor having the general formula.

This phosphor had a much weaker afterglow component than a comparative product containing no cerium, and was almost the same as curve 1 in FIG. Also, the brightness is X compared to a comparative product that does not contain cerium.
It improved by 20% with line stimulation and by 10% with electron beam stimulation. Furthermore, when this phosphor was used in an intensifying screen, the contrast was 5% higher than that of a screen that did not contain cerium.
Example 10 Yttrium oxide, gadolinium oxide, lanthanum oxide,
A phosphor was produced in the same manner as in Example 1 by mixing appropriate amounts of lutetium oxide, terbium, and cerium to obtain a phosphor having the general formula.

This phosphor had a much weaker afterglow component than a comparative product containing no cerium, and was almost the same as curve 1 in FIG. Furthermore, the brightness was almost the same for X-ray stimulation and electron beam stimulation. When this phosphor was used in an intensifying screen, the contrast was improved by 10% compared to a screen that did not contain cerium. Example 11 A phosphor was manufactured in the same manner as in Example 1 by mixing appropriate amounts of yttrium oxide, gadolinium oxide, terbium, and cerium to obtain a phosphor having the general formula.

This phosphor had a much weaker afterglow component than a comparative product containing no cerium, and was almost the same as curve 1 in FIG. In addition, the brightness was almost the same in X-ray stimulation and electron beam stimulation as compared to a comparative product that did not contain cerium. When this phosphor was used in an intensifying screen, the contrast was improved by 50% compared to one without cerium. Example
12 A phosphor was produced in the same manner as in Example 1 by mixing appropriate amounts of yttrium oxide, terbium, and cerium to obtain a phosphor having the general formula.

This phosphor had a much weaker afterglow component than a comparative product that did not contain cerium, and its brightness improved by 3% when stimulated with X-rays and by 2% when stimulated with electron beams. Furthermore, when this phosphor was used in an intensifying screen, the contrast was improved by 15% compared to a screen that did not contain cerium. In addition, the oscilloscope tube for synchroscope coated with this phosphor is different from conventional ZnS/Cu,
．． Compared to those using Cl, there is no saturation of current density and the brightness is 20% when used at 10uA/Cd and 20KV.
Improved. Furthermore, this phosphor has an extremely weak afterglow component compared to ZnS/CuCl, and has a uniform body color, making the image easier to see and contrast improved by 30%. This phosphor has good saturation characteristics as described above, so it can also be applied to color cathode ray tubes. Example 13 A phosphor was manufactured in the same manner as in Example 1 by mixing appropriate amounts of lanthanum oxide, terbium, and cerium to obtain a phosphor having the general formula.

This phosphor had a much weaker afterglow component than a comparative product that did not contain cerium, and its brightness was improved by 5% when stimulated with X-rays and by 2% when stimulated with electron beams. Furthermore, when this phosphor was used in an intensifying screen, the contrast was improved by 10% compared to a comparative product that did not contain cerium. In addition, when we prototyped a 20W mercury lamp using this phosphor and investigated its emission characteristics, we found that Zn2SiO4/Zn2SiO4, which has traditionally been used as a green light source,
The brightness was improved by 30% compared to a mercury lamp using Mn. Because of the above, it can be used as a green light source for Xerox, etc.

[Brief Description of the Drawings] Figures 1 and 2 are characteristic diagrams showing the relationship between afterglow intensity and decay time depending on the amount of cerium added in the terbium activated rare earth oxysulfide phosphor of the present invention, and Figure 3 is a characteristic diagram showing the relationship between afterglow intensity and decay time depending on the amount of cerium added. is a characteristic diagram showing the luminescence intensity of the phosphor depending on the amount of cerium added in the terbium-activated rare earth oxysulfide phosphor of the present invention. FIG. 3 is a characteristic diagram showing the reflection spectrum distribution and emission spectrum distribution of the id fluorescent material.

Claims (1)

[Claims] 1 General formula (1-x-y)M_2O_2S・XTb_2O_2S・
A phosphor comprising yCe_2O_2\S\. However, M is a rare earth element consisting of at least one of Y, Gd, La, and Lu, 5×10^-^5≦x≦1×1
0＾-＾1, 5×10＾-＾7≦y≦1×10＾-＾3
.