JP2001131546A - Rare-earth oxysulfide phosphor and radiological image- conversion screen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-intensity rare-earth oxysulfide phosphor and a radiological image-conversion screen excellent in sensitivity and sharpness. SOLUTION: The rare-earth oxysulfide phosphor is represented by the composition formula: (Ln1-x, REx)2O2S (wherein Ln is at least one selected from the group consisting of Y, Gd, La and Lu; RE is at least one selected from the group consisting of Tb, Eu, Tm and Pr; and x is a number meeting the condition: 1×10-3<=x<=1×10-1) and comprises at least one alkali metal element selected from the group consisting of cesium(Cs) and rubidium(Rb). The radiological image-conversion screen is formed by laminating a phosphor layer made of the phosphor on a substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare earth oxysulfide phosphor which emits light with high luminance under the excitation of radiation such as X-rays, and a high-sensitivity radiation image conversion screen using the same.

[0002]

2. Description of the Related Art Rare earth oxysulfide phosphors have been conventionally used in radiographic intensifying screens, color TV cathode-ray tubes, and the like as phosphors that emit light with high brightness when excited by electron beams or X-rays. Among them, gadolinium oxysulfide phosphor {(Gd, Tb) ₂ O ₂ S} which emits green or bluish green light activated by Tb is particularly suitable for a radiation image conversion screen (hereinafter, referred to as a radiographic intensifying screen or a fluorescent screen). “These are collectively referred to simply as“ image conversion sheet ”) and are widely used in the field of medical diagnosis and industrial nondestructive inspection.

[0003] However, it is always desired to further improve the sensitivity and image quality of an imaging system for the purpose of medical diagnosis and industrial non-destructive inspection in order to further enhance diagnostic and inspection capabilities. An image conversion sheet using an object phosphor is no exception. For this purpose, much higher sensitivity of the phosphor used in the image conversion sheet and improvement of the structure and manufacturing method of the image conversion sheet have been made in many cases.

Further, in recent years, a radiation diagnostic method has been proposed in which a radiation image revealed on an image conversion sheet is detected by an image pickup device such as a CCD camera, the image is digitized, and in some cases, the image is transmitted. As the spectral sensitivity of the imaging device used has been widened to a wide range from blue to red, the image conversion sheet used in combination with this has been used in addition to the conventional one that emits light from blue to green. In addition, an image conversion sheet that emits light from blue to red has become useful if it has high sensitivity and high image quality.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rare earth oxysulfide phosphor having a higher luminance than that of a conventional phosphor as an X-ray phosphor. Another object of the present invention is to provide an image conversion sheet having improved photographic sensitivity and sharpness as compared with conventional ones.

[0006]

In order to increase the sensitivity and the resolution of an image conversion sheet, it is first important to improve the luminance of the phosphor used as the phosphor layer, and the filling density of the phosphor in the phosphor layer is reduced. Improvement is important. The present inventors, in order to achieve the above object, when manufacturing these rare earth oxysulfide phosphors, control the particle shape from the stage of particle growth, in order to obtain a high brightness and rounded particle shape, various Study was carried out. As a result, by adding a specific amount of an alkali metal element during the synthesis of the phosphor, the particle shape of the obtained phosphor is improved, and when an image conversion sheet having a phosphor layer composed of this phosphor is produced, The present inventors have found that the object can be achieved, and arrived at the present invention.

That is, the present invention has the following configuration. (1) The composition formula is (Ln _1-x , RE _x ) ₂ O ₂ S (where Ln is at least one of Y, Gd, La and Lu, and RE is Tb, Eu, Tm and Pr) X is at least one, and x is 1 × 10 ⁻³ ≦ x ≦ 1 × 10
^This is a number that satisfies the condition of ⁻¹ . ) And containing an alkali metal element selected from at least one of cesium (Cs) and rubidium (Rb). (2) The content of the alkali metal element is 0.2 to 50 p
pm range, the rare earth oxysulfide phosphor according to the above (1),

(3) In a radiation image conversion screen in which a phosphor layer formed by dispersing a phosphor in a binder is formed on a support, the phosphor has a composition formula (Ln _1-x , RE
_x ) ₂ O ₂ S (where Ln is Y, Gd, La and L
u is at least one of RE, T is at least one of Tb, Eu, Tm and Pr, and x is 1 × 10 ^−3.
≦ x ≦ ¹ × 10 ⁻¹ ) and cesium (Cs) and rubidium (Rb)
A radiation image conversion screen comprising a rare earth oxysulfide phosphor containing an alkali metal element selected from at least one of the following. (4) The content of the alkali metal element is 0.2 to 50.
The radiation image conversion screen according to the above (3), which is in the range of ppm.

(5) The radiation image conversion screen according to (4), wherein the content of the alkali metal element is in the range of 0.5 to 10 ppm. (6) The radiation image conversion screen according to any one of (3) to (5), wherein the Ln is Gd and the RE is Tb.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The method for producing a rare earth oxysulfide phosphor according to the present invention comprises a conventional rare earth oxysulfide phosphor except that a specific amount of a compound of Cs and / or Rb is added to a mixture of the raw materials in the phosphor production process, followed by firing. It is the same method as the body, and is produced as follows, for example, using the following as the phosphor raw material.

Raw materials: oxides of Gd, Y, La and Lu, or rare earth elements (Ln) which can be converted to oxides at high temperatures, such as nitrates, carbonates, sulfates and halides thereof
At least one of the following compounds: Raw materials: oxides of Tb, Eu, Tm and Pr or rare earth (RE) compounds which can be converted to oxides at high temperatures, such as nitrates, carbonates, sulfates, halides, etc. At least one of the compounds, raw material: sulfur (S), raw material: at least one of alkali metal compounds such as halides and carbonates of Cs and Rb, and raw materials: sodium carbonate (Na ₂ CO ₃ ), carbonic acid Fluxing agents such as potassium (K ₂ CO ₃ ) and tri-potassium phosphate (K ₃ PO ₄ )

The above raw materials and stoichiometrically (Ln
_1-x , RE _x ) ₂ O ₃ (where Ln is Y, Gd, La
And at least one of Lu, RE is Tb, Eu,
At least one of Tm and Pr, and x is 1 ×
It is a number that satisfies the condition of 10 ⁻³ ≦ x ≦ ¹ × 10 ⁻¹ . Hereinafter, the same applies. ), And the above-mentioned raw materials to be converted into oxysulfides and the above-mentioned raw materials are sufficiently mixed with each other to prepare a phosphor raw material mixture. The raw material is added in a slightly excessive amount than the stoichiometric amount in order to complete the oxysulfide formation of the mixture raw material, and the raw material does not necessarily contain the entire amount of the added alkali metal element in the phosphor crystal. In a process such as the above, a part thereof is washed out of the phosphor crystal, so that this is also added in excess of the amount desired to be contained in the phosphor. When a raw material is added, the amount of the raw material added is extremely small compared to other raw materials. Therefore, a certain amount that can be weighed is weighed, and dissolved and diluted in an appropriate solvent. May be added and mixed.

The raw material and a predetermined amount thereof are dissolved in a mineral acid such as nitric acid or the like, and oxalic acid is added thereto to form an oxalate of Ln and RE. May be generated and subjected to solid-liquid separation, and then heat-treated to form a mixed oxide, and then mixed with other raw materials to obtain a phosphor raw material mixture of the present invention.

Next, the mixture of these phosphor raw materials is filled in a heat-resistant container such as alumina, and is heated to 1100 to 1250 ° C. in the atmosphere.
For about 3 to 10 hours. After firing, the fired cake is immersed in water to form a slurry, washed, dispersed, dried,
The phosphor of the present invention is obtained through each post-processing operation after firing, which is generally performed in the manufacture of a phosphor such as sieving. If the obtained phosphor has a body color, this is further
When the heat treatment is performed at a temperature of 00 to 500 ° C., the body color disappears, and the light emission luminance may be further improved.

On the other hand, the image conversion sheet of the present invention comprises the rare earth oxysulfide phosphor of the present invention containing at least one of the specific amounts of Cs and Rb produced as described above as a phosphor layer. It is manufactured in the same manner as a conventional image conversion sheet except that it is used as a phosphor layer.

That is, binder resins such as nitrified cotton, cellulose acetate, ethyl cellulose, polyvinyl butyral, linear polyester, polyvinyl acetate, vinylidene chloride-vinyl chloride copolymer, vinyl chloride-vinyl acetate copolymer and the rare earth oxysulfide of the present invention. A phosphor is mixed with the mixture, and an organic solvent such as ethanol, butyl acetate, ethyl acetate, ethyl ether, or xylene is added to the mixture to prepare a phosphor coating solution having an appropriate viscosity. The amount of the binder resin in the phosphor coating solution is 1 to the phosphor in the phosphor layer in that the sharpness and durability of the obtained image conversion sheet are not reduced.
Preferably, the content is 10 to 10% by weight. Next, the phosphor coating solution is coated with a knife coater, a die coater, or the like on a support made of cellulose acetate, cellulose propionate, cellulose acetate butyrate, polyethylene terephthalate, baryta paper, resin-coated paper, ordinary paper, aluminum alloy foil, or the like. Apply uniformly and dry to form a phosphor layer, and further apply a protective film coating solution in which a resin such as cellulose acetate, nitrocellulose, or cellulose acetate butyrate is dissolved in a solvent, if necessary, and then dry. Alternatively, a protective film formed in advance, for example, a transparent film such as polyethylene terephthalate, polyethylene naphthalate, or polyethylene is laminated on the phosphor layer to form a protective film, thereby obtaining the image conversion sheet of the present invention.

The phosphor coating weight of the phosphor layer after drying is about 10 to 200 mg / cm ² , more preferably 3 to 200 mg / cm ^2.
Suitably, it is 0 to 150 mg / cm ² . The phosphor layer provided on the support is not necessarily required to be a single layer, and for the purpose of improving image quality and sensitivity, the rare earth oxysulfide phosphor of the present invention and a phosphor having a different composition from the phosphor are used. Or two or more types of phosphor coatings composed of two types of phosphors having the same composition as the rare earth oxysulfide phosphor of the present invention but different particle size distributions. An image conversion sheet composed of a plurality of phosphor layers, which are sequentially coated with a liquid, dried, and laminated, may be used.

FIG. 1 shows (Gd) of the present invention containing Rb or Cs having different contents as alkali metals.
_0.996 , Tb _0.004 ) ₂ O ₂ S A phosphor was used as a phosphor layer to produce an image conversion sheet.
Relationship between the content (ppm value) of alkali metal in the phosphor layer of each image conversion sheet and the photographic sensitivity of the image conversion sheet when X-rays with a tube voltage of 80 kV were irradiated in close contact with the radiographic film. And curves a and b in FIG. 1 are the case where the alkali metal is Rb and the case where the alkali metal is Cs, respectively. The content of Cs and / or Rb in each phosphor is an analysis value obtained by dissolving each phosphor and quantifying the content by a glow discharge mass spectrometer.

As can be seen from FIG. 1, the optimum content of the rare earth oxysulfide phosphor used as the phosphor layer of the image conversion sheet is optimum when the alkaline earth metal contained in the phosphor is Rb or Cs. Is slightly different, but when the content of these alkali metal elements is about 0.2 to 30 ppm, the photographic sensitivity of an image conversion sheet using the same is based on the conventional rare earth oxysulfide phosphor containing no alkali metal. The content of the alkaline earth metal was 0.5% in terms of photographic sensitivity when the image conversion sheet was improved.
It is particularly preferable to use a phosphor of 10 to 10 ppm in the phosphor layer. Although not illustrated, the emission luminance of the rare-earth oxysulfide phosphor powder of the present invention containing an alkali metal under X-ray excitation also shows the conventional rare-earth acid as long as the alkali metal content is within a specified amount range. It was improved more than the sulfide phosphor, and showed almost the same tendency as in FIG. 1 between the emission luminance and the content of the alkali metal element in the phosphor. FIG.
In the above, the case where Ln is Gd and RE is Tb is exemplified, but also when Ln is other than Gd and when RE is other than Tb, the emission color specific to the activator (RE) is also different. Although emission was observed, there was almost the same tendency as shown in FIG. 1 between the content of the alkali metal in the phosphor and the emission luminance under X-ray excitation. If it is within the range, the brightness is higher than that of the rare earth oxysulfide phosphor not containing these, and the image conversion sheet using these phosphors as the phosphor layer can fluoresce the rare earth oxysulfide phosphor containing no alkali metal. The sensitivity was improved as compared with the image conversion sheet used as the body layer. In addition, about these image conversion sheets whose activator (RE) is other than Tb, each image conversion sheet was irradiated with X-rays, and the emission luminance at that time was measured by a luminance meter, and the effect was confirmed. Further, for example, as disclosed in JP-A-7-278540, a small amount of zinc (Zn), cerium (Ce), scandium (Sc),
For the rare earth oxysulfide phosphor to which neodymium (Nd) or the like has been added, the effect of improving the emission luminance was similarly observed by further adding Cs and / or Rb to the phosphor.

The reason why the sensitivity of the phosphor of the present invention is improved when the phosphor is used as an image conversion sheet is that the basic crystal structure of the rare earth oxysulfide phosphor particles is hexagonal and that the crystal is likely to be horny. In spite of the habit, the rare earth oxysulfide phosphor of the present invention containing a specific amount of Rb and / or Cs improves the emission luminance and the shape of the phosphor particles is rounded. This is presumably because the formation of the phosphor layer by using the phosphor increases the packing density of the phosphor in the phosphor layer. As described above, the particle shape of the phosphor rare earth oxysulfide of the present invention is spherical rather than square, and when this phosphor is used as the phosphor layer, the phosphor packing density increases. Is to improve the photo sensitivity,
Resolution and sharpness could be greatly improved. It should be noted that the rare earth oxysulfide phosphor of the present invention emits light with high luminance even when excited by an electron beam or ultraviolet light.

[0021]

[Example 1]

Gadolinium oxide (Gd ₂ O ₃ ) 722.3 g Terbium oxide (Tb ₄ O ₇ ) 3.0 g 7.2 g of cesium chloride (CsCl) were weighed and mixed in advance, and then potassium dihydrogen phosphate (KH) was added thereto. ₂ PO ₄₎ 36.3 g of sodium carbonate _(Na 2 _CO 3) was added to 280.0g of sulfur (S) 220.0 g was uniformly mixed. The raw material mixture was filled in an alumina crucible and fired at 1200 ° C. for 5 hours in the atmosphere. The obtained calcined product is immersed in water to form a slurry, washed with water, washed with 0.5N hydrochloric acid, further washed with water, dehydrated, dried, and sieved.
The rare earth oxysulfide phosphor of Example 1 was obtained as _0.996 Tb _0.004 ) ₂ O ₂ S and containing Cs. As a result of analysis, this phosphor contained 2.5 ppm of Cs, but Rb was less than the lower limit of detection of 0.1 ppm.

Next, 8 parts by weight of the phosphor of Example 1, 1 part by weight of polyvinyl butyral resin (binder) and an organic solvent were added and mixed to prepare a phosphor coating solution. This phosphor coating solution is uniformly coated on a polyester support containing a titanium oxide powder and having a light reflection effect using a knife coater so that the phosphor coating weight after drying is about 50 mg / cm ² . It was dried to form a phosphor layer. Next, a protective layer made of a transparent polyester resin film having a thickness of about 6 μm was laminated on the surface of the phosphor layer to obtain an image conversion sheet of Example 1.

Comparative Example 1 A composition formula (Gd _0.996 Tb) was used in the same manner as in the phosphor of Example 1 except that cesium chloride (CsCl) was not used as a phosphor raw material.
_0.004 ) ₂ O ₂ S was obtained as the rare earth oxysulfide phosphor of Comparative Example 1. As a result of the analysis, this phosphor was found to be Cs, Rb
Both were below the detection lower limit of 0.1 ppm.

Next, Comparative Example 1 was used instead of the phosphor of Example 1.
An image conversion sheet of Comparative Example 1 was produced in the same manner as the image conversion sheet of Example 1 except that the phosphor was used as a phosphor coating solution.

Examples 2 to 6 In the phosphor raw material of Example 1, 3.6 g, 10.6 g, 14.4 g, 21.6 g, and 3.6 g of cesium chloride (CsCl) were used instead of 7.2 g of cesium chloride (CsCl).
The composition formula was (Gd) in the same manner as in the phosphor of Example 1 except that 36.0 g of cesium chloride (CsCl) was used.
Each of the rare earth oxysulfide phosphors of Examples 2 to 6 which was _0.996 Tb _0.004 ) ₂ O ₂ S and contained Cs was obtained.
As a result of the analysis, this phosphor showed Cs of 1.3 pp each.
m, 3.8 ppm, 5.2 ppm, 7.0 ppm and 9.8 ppm, but Rb was less than the lower limit of detection of 0.1 ppm.

Next, Embodiment 2 is replaced with the phosphor of Embodiment 1.
Each of Examples 2 to 6 was performed in the same manner as the image conversion sheet of Example 1 except that each of the phosphors was used as a coating solution for each phosphor.
6 was manufactured.

Examples 7 to 12 In the phosphor raw material of Example 1, 3.6 g, 7.2 g, 10.6 g, 14.4 g, and 3.6 g of cesium chloride (CsCl) were used instead of 7.2 g of cesium chloride (CsCl).
21.6 g, 36.0 g of rubidium chloride (RbCl)
The composition formula is (Gd _0.996 Tb _0.004 ) ₂ O ₂ S and Rb is the same as in the phosphor of Example 1 except that
Each of the rare earth oxysulfide phosphors of Examples 7 to 12 was obtained. As a result of analysis, this phosphor had Rb of 1.
1 ppm, 2.0 ppm, 3.1 ppm, 4.2 pp
m, 6.2 ppm and 8.5 ppm,
Cs was less than the lower limit of detection of 0.1 ppm.

Next, Embodiment 7 is replaced with the phosphor of Embodiment 1.
Example 7 was the same as the image conversion sheet of Example 1 except that each of the phosphors of Nos. 1 to 12 was used to prepare each phosphor coating solution.
To 12 image conversion sheets were produced.

The photographic sensitivity and sharpness of the image conversion sheets of Examples 1 to 12 and Comparative Example 1 were measured, and the results were used for the production of each image conversion sheet.
Table 1 shows the composition of each phosphor of Example 12 and Comparative Example 1, the content of alkali metal Cs and / or Rb, and the average particle size thereof.

In Table 1, the content of Cs and / or Rb in each phosphor is an analysis value obtained by quantification using a glow discharge mass spectrometer. The photographic sensitivity of the image conversion sheet is determined by bringing each image conversion sheet into close contact with an orthochromatic X-ray photographic film (film), and applying a tube voltage of 80 k
After the X-rays of V were exposed, each film was developed, the degree of blackening of each film was determined, and the relative degree of blackening of the film when the image conversion sheet of Comparative Example 1 was used was taken as 100. Indicated by value. The sharpness of the image conversion sheet is determined by closely contacting each image conversion sheet with the film, photographing an X-ray test chart for inspecting the characteristics of the image conversion sheet, and analyzing the obtained captured images by a known method. The correlation between the frequency and the MTF was obtained, and each MTF value at a spatial frequency of 2 lines / mm was shown as a relative value to the MTF value of the image conversion sheet of Comparative Example 1.

[0031]

[Table 1]

Example 13 Gadolinium oxide (Gd ₂ O ₃ ) 703.4 g Europium oxide (Eu ₂ O ₃ ) 21.1 g Cesium chloride (CsCl) 11.0 g was mixed in advance, and then potassium dihydrogen phosphate (KH ₂ PO ₄ ) 36.3 g Sodium carbonate (Na ₂ CO ₃ ) 250.0 g Sulfur (S) 220.0 g was added, and the mixture was mixed in the same manner as in Example 1 except that a raw material mixture was used. And the composition formula is (Gd _0.97 Eu
_0.03 ) Example 13 which is ₂ O ₂ S and contains Cs
Of rare earth oxysulfide phosphor was obtained. As a result of analysis, this phosphor contained 3.5 ppm of Cs, but Rb was below the lower limit of detection of 0.1 ppm.

Next, Embodiment 1 is replaced with the phosphor of Embodiment 1.
An image conversion sheet of Example 13 was produced in the same manner as the image conversion sheet of Example 1 except that the phosphor of Example 3 was used as a phosphor coating solution.

[Examples 14 and 15] In the phosphor raw materials of Example 1, 18.0 g of cesium bromide (CsBr) and 18.0 g of cesium bromide (CsBr) were used instead of 7.2 g of cesium chloride (CsCl).
The composition formula was (Gd) in the same manner as in the phosphor of Example 1, except that 1.0 g of cesium sulfate (Cs ₂ SO ₄ ) was used.
The respective rare earth oxysulfide phosphors of Examples 14 and 15 which were _0.97 Eu _0.03 ) ₂ O ₂ S and contained Cs were obtained. As a result of analysis, this phosphor had a Cs of 3.8 p each.
pm and 3.0 ppm, but Rb was less than the lower limit of detection of 0.1 ppm.

Next, the first embodiment is replaced with the phosphor of the first embodiment.
The image conversion sheets of Examples 14 and 15 were manufactured in the same manner as the image conversion sheet of Example 1 except that each of the phosphors of Examples 4 and 15 was used as a phosphor coating solution.

Embodiments 16 to 18 In the phosphor raw materials of Embodiment 1, 7.0 g of rubidium chloride (RbCl) and 7.0 g of rubidium chloride (RbCl) were used instead of 7.2 g of cesium chloride (CsCl).
5.0 g of rubidium bromide (RbBr) and 11.0 g
Except that rubidium nitrate (RbNO ₃ ) was used, and the composition formula was (Gd
The respective rare earth oxysulfide phosphors of Examples 16, 17 and 18 which were _0.97 Eu _0.03 ) ₂ O ₂ S and contained Rb were obtained. As a result of analysis, this phosphor contained 1.5 ppm, 2.8 ppm, and 1.8 ppm of Rb, respectively, but Cs was less than the detection lower limit of 0.1 ppm in each case.

Next, in the same manner as in the image conversion sheet of Example 1, except that the phosphors of Examples 14 and 15 were used instead of the phosphor of Example 1 to prepare a phosphor coating solution. 16 to 18 image conversion sheets were produced.

Comparative Example 2 The composition formula was (Gd _0.97 E) in the same manner as in the phosphor of Example 13 except that cesium chloride (CsCl) was not used as the phosphor raw material.
The rare earth oxysulfide phosphor of Comparative Example 2 which was u _0.03 ) ₂ O ₂ S was obtained. As a result of the analysis, this phosphor was found to be Cs, Rb
Both were below the detection lower limit of 0.1 ppm.

Next, the image conversion sheet of Comparative Example 2 was prepared in the same manner as the image conversion sheet of Example 1 except that the phosphor of Comparative Example 2 was used instead of the phosphor of Example 1 to form a phosphor coating solution. A sheet was manufactured.

With respect to the image conversion sheets of Examples 13 to 18 and Comparative Example 2, the screen luminance was measured, and the compositions of the phosphors of Examples 13 to 18 and Comparative Example 2 used for producing each image conversion sheet were Table 2 shows the content of Cs and / or Rb of the alkali metal in the phosphor and the average particle size thereof measured in the same manner as in Examples 1 to 12 and Comparative Example 1. The screen luminance of each image conversion sheet was measured by a luminance meter (Topcon Co., Ltd., color luminance meter, type BM-5) while continuously emitting X-rays at a tube voltage of 80 kV and a tube current of 3 mA. And relative values to the emission luminance of the image conversion sheet of Comparative Example 2.

[0041]

[Table 2]

Example 19 Gadolinium oxide (Gd ₂ O ₃ ) 724.5 g Praseodymium oxide (Pr ₇ O ₁₁ ) 0.7 g Cesium chloride (CsCl) 8.0 g was mixed in advance, and then potassium dihydrogen phosphate (KH ₂ PO ₄ ) 25.0 g Sodium carbonate (Na ₂ CO ₃ ) 280.0 g Sulfur (S) 220.0 g was added and uniformly mixed to obtain a raw material mixture.
The composition formula is (Gd _0.999 Pr _0.001 ) ₂ O _{2 in the same} manner as in the phosphor of Example 1 except that the composition is fired at 0 ° C. for 4 hours.
The rare earth oxysulfide phosphor of Example 19 which was S and contained Cs was obtained. As a result of analysis, this phosphor had a Cs of 2.0
ppm, but Rb was below the detection limit of 0.1 pp
m.

Next, Embodiment 1 is replaced with the phosphor of Embodiment 1.
Example 1 except that a phosphor coating solution was prepared using the phosphor of Example 9.
The image conversion sheet of Example 19 was manufactured in the same manner as the image conversion sheet of Example 19 above.

Comparative Example 3 The composition formula was (Gd _0.999 Pr) in the same manner as in the phosphor of Example 19 except that cesium chloride (CsCl) was not used as the phosphor raw material.
The rare earth oxysulfide phosphor of Comparative Example 3 which was _0.001 ) ₂ O ₂ S was obtained. As a result of the analysis, this phosphor was found to be Cs, Rb
Both were below the detection lower limit of 0.1 ppm.

Next, the image conversion sheet of Comparative Example 3 was prepared in the same manner as the image conversion sheet of Example 1 except that the phosphor of Comparative Example 3 was used instead of the phosphor of Example 1 to form a phosphor coating solution. A sheet was manufactured.

In the same manner as in Examples 13 to 18 and Comparative Example 2 described above, the screen luminance of the image conversion sheets of Example 19 and Comparative Example 3 was measured, and the image conversion sheets used for manufacturing each image conversion sheet were measured. Table 3 shows the composition of the phosphor of Example 19 and Comparative Example 3, the content of Cs and / or Rb of the alkali metal measured in the same manner as in Examples 1 to 12 and Comparative Example 1, and the average particle diameter of the phosphor. Indicated. In Table 3, the screen luminance of the image conversion sheet of Example 19 is shown as a relative value to the screen luminance of the image conversion sheet of Comparative Example 3.

Example 20 447.0 g of yttrium oxide (Y ₂ O ₃ ) 7.4 g of terbium oxide (Tb ₄ O ₇ ) 6.0 g of cesium chloride (CsCl) were mixed in advance, and then tripotassium phosphate (CsCl) was added. K ₃ PO ₄ ) 25.0 g Sodium carbonate (Na ₃ CO ₃ ) 200.0 g Sulfur (S) 160.0 g was added and uniformly mixed to obtain a raw material mixture.
The rare earth oxysulfide of Example 20 having a composition formula of (Y _0.99 Tb _0.01 ) ₂ O ₂ S and containing Cs in the same manner as the phosphor of Example 1 except that the phosphor was fired at 0 ° C. for 10 hours. Fluorescent substance was obtained. As a result of analysis, this phosphor had a Cs of 2.0 pp.
However, Rb was less than the lower limit of detection of 0.1 ppm.

Next, the second embodiment is replaced with the phosphor of the first embodiment.
Example 1 except that a phosphor coating solution was prepared by using phosphor 0
The image conversion sheet of Example 20 was manufactured in the same manner as the image conversion sheet of Example 20.

Comparative Example 4 The composition formula was (Y _0.99 Tb _0.01 ) in the same manner as in the phosphor of Example 20 except that cesium chloride (CsCl) was not used as the phosphor raw material.
A rare earth oxysulfide phosphor of Comparative Example 4, which was ₂ O ₂ S, was obtained. As a result of analysis of this phosphor, both Cs and Rb were below the detection lower limit of 0.1 ppm.

Next, the image conversion sheet of Comparative Example 4 was produced in the same manner as the image conversion sheet of Example 1 except that the phosphor of Comparative Example 4 was used instead of the phosphor of Example 1 to form a phosphor coating solution. A sheet was manufactured.

In the same manner as in Examples 13 to 18 and Comparative Example 2, the screen brightness of the image conversion sheets of Example 20 and Comparative Example 4 was measured, and the image conversion sheets used for manufacturing each image conversion sheet were measured. Table 3 shows the composition of the phosphor of Example 20 and Comparative Example 4, the content of Cs and / or Rb of the alkali metal measured in the same manner as in Examples 1 to 12 and Comparative Example 1, and the average particle diameter of the phosphor. Indicated. In Table 3, the screen luminance of the image conversion sheet of Example 20 is shown as a relative value to the screen luminance of the image conversion sheet of Comparative Example 4.

Example 21 Lanthanum oxide (La ₂ O ₃ ) 645.0 g Terbium oxide (Tb ₄ O ₇ ) 7.4 g Cesium chloride (CsCl) 7.0 g was previously mixed, and then tripotassium phosphate (CsCl) was added. K ₃ PO ₄ ) 32.0 g Sodium carbonate (Na ₃ CO ₃ ) 200.0 g Sulfur (S) 160.0 g was added and uniformly mixed to obtain a raw material mixture.
The rare earth oxysulfide of Example 21 having a composition formula of (La _0.99 Tb _0.01 ) ₂ O ₂ S and containing Cs in the same manner as the phosphor of Example 1 except that the phosphor was fired at 0 ° C. for 6 hours. Fluorescent substance was obtained. As a result of analysis, this phosphor had a Cs of 2.0 pp.
However, Rb was less than the lower limit of detection of 0.1 ppm.

Next, the second embodiment is replaced with the phosphor of the first embodiment.
Example 1 except that a phosphor coating solution was prepared using the phosphor of Example 1.
The image conversion sheet of Example 21 was manufactured in the same manner as the image conversion sheet of Example 21.

Comparative Example 5 The composition formula was (La _0.99 T) in the same manner as the phosphor of Example 21 except that cesium chloride (CsCl) was not used as the phosphor raw material.
The rare earth oxysulfide phosphor of Comparative Example 5 which was b _0.01 ) ₂ O ₂ S was obtained. As a result of the analysis, this phosphor was found to be Cs, Rb
Both were below the detection lower limit of 0.1 ppm.

Next, the image conversion sheet of Comparative Example 5 was prepared in the same manner as the image conversion sheet of Example 1 except that the phosphor of Comparative Example 5 was used instead of the phosphor of Example 1 to form a phosphor coating solution. A sheet was manufactured.

In the same manner as in Examples 13 to 18 and Comparative Example 2, the screen luminance of the image conversion sheets of Example 21 and Comparative Example 5 was measured, and the image conversion sheets used in the production of each image conversion sheet were measured. The compositions of the phosphors of Example 21 and Comparative Example 5, the contents of Cs and / or Rb of the alkali metal measured in the same manner as in Examples 1 to 12 and Comparative Example 1, and the average particle diameter thereof are shown in Table 3. In Table 3, the screen luminance of the image conversion sheet of Example 21 is shown as a relative value to the screen luminance of the image conversion sheet of Comparative Example 5.

Example 22 Lutetium oxide (Lu ₂ O ₃ ) 788.0 g Terbium oxide (Tb ₄ O ₇ ) 7.4 g Cesium chloride (CsCl) 10.0 g was mixed in advance, and then tripotassium phosphate (CsCl) was added. K ₃ PO ₄ ) 40.0 g Sodium carbonate (Na ₃ CO ₃ ) 300.0 g Sulfur (S) 230.0 g was added and uniformly mixed to obtain a raw material mixture.
The composition formula is (Lu _0.99 Tb _0.01 ) ₂ O _{2 in the same} manner as in the phosphor of Example 20, except that the phosphor is fired at 0 ° C. for 10 hours.
The rare earth oxysulfide phosphor of Example 22 which was S and contained Cs was obtained. As a result of analysis, this phosphor had a Cs of 2.0
ppm, but Rb was below the detection limit of 0.1 pp
m.

Next, the image conversion sheet of Example 22 was used in the same manner as the image conversion sheet of Example 1 except that the phosphor of Example 22 was used instead of the phosphor of Example 1 to form a phosphor coating solution. A sheet was manufactured.

Comparative Example 6 The composition formula was (La _0.99 T) in the same manner as in the phosphor of Example 22 except that cesium chloride (CsCl) was not used as the phosphor raw material.
b _0.01 ) ₂ O ₂ S was obtained as the rare earth oxysulfide phosphor of Comparative Example 6. As a result of the analysis, this phosphor was found to be Cs, Rb
Both were below the detection lower limit of 0.1 ppm.

Next, Comparative Example 6 was used instead of the phosphor of Example 1.
An image conversion sheet of Comparative Example 6 was produced in the same manner as the image conversion sheet of Example 1 except that the phosphor was used as a phosphor coating solution.

In the same manner as in Examples 13 to 18 and Comparative Example 2 described above, the screen luminance of the image conversion sheets of Example 22 and Comparative Example 6 was measured, and the image conversion sheets used for manufacturing each image conversion sheet were measured. Table 3 shows the compositions of the phosphors of Example 22 and Comparative Example 6, the contents of Cs and / or Rb of the alkali metal measured in the same manner as in Examples 1 to 12 and Comparative Example 1, and the average particle size thereof. In Table 3, the screen luminance of the image conversion sheet of Example 22 is shown as a relative value to the screen luminance of the image conversion sheet of Comparative Example 6.

Example 23 Yttrium oxide (Y ₂ O ₃ ) 133.8 g Gadolinium oxide (Gd ₂ O ₃ ) 504.0 g Terbium oxide (Tb ₄ O ₇ ) 3.0 g Thulium oxide (Tm ₂ O ₃ ) 0 8.8 g Cesium chloride (CsCl) 10.0 g was previously mixed, then potassium dihydrogen phosphate (KH ₂ PO ₄ ) 32.0 g sodium carbonate (Na ₃ CO ₃ ) 250.0 g sulfur (S) 190.0 g In addition, the mixture is uniformly mixed to obtain a raw material mixture,
Except for baking at 0 ° C. for 5 hours, the composition formula was (Y _0.3 Gd _0.695 Tb _0.004 ) in the same manner as in the phosphor of Example 1.
A rare earth oxysulfide phosphor of Example 20 was obtained which was Tm _0.001 ) ₂ O ₂ S and contained Cs. As a result of analysis, this phosphor contained 3.0 ppm of Cs, but Rb was less than the lower limit of detection of 0.1 ppm.

Next, Embodiment 2 is replaced with the phosphor of Embodiment 1.
Example 1 except that the phosphor of Example 3 was used as a phosphor coating solution.
The image conversion sheet of Example 23 was manufactured in the same manner as the image conversion sheet of Example 23.

Comparative Example 7 The composition formula was (Y _0.3 Gd _0.695 T) in the same manner as in the phosphor of Example 23 except that cesium chloride (CsCl) was not used as the phosphor raw material.
b _0.004 Tm _0.001 ) ₂ O ₂ S to obtain a rare earth oxysulfide phosphor of Comparative Example 7. As a result of analysis of this phosphor, both Cs and Rb were below the detection lower limit of 0.1 ppm.

Next, Comparative Example 7 was used instead of the phosphor of Example 1.
An image conversion sheet of Comparative Example 7 was produced in the same manner as the image conversion sheet of Example 1 except that the phosphor was used as a phosphor coating solution.

In the same manner as in Examples 13 to 18 and Comparative Example 2 described above, the screen luminance of the image conversion sheets of Example 23 and Comparative Example 7 was measured, and the image conversion sheets used for manufacturing each image conversion sheet were measured. The compositions of the phosphors of Example 23 and Comparative Example 7, the contents of alkali metal Cs and / or Rb measured in the same manner as in Examples 1 to 12 and Comparative Example 1, and the average particle diameter thereof are shown in Table 3. In Table 3, the screen luminance of the image conversion sheet of Example 23 is shown as a relative value to the screen luminance of the image conversion sheet of Comparative Example 7.

[0067]

[Table 3]

[0068]

The rare-earth oxysulfide phosphor of the present invention has the above-mentioned structure, so that it emits light of higher luminance than that of the conventional phosphor particularly under X-ray excitation, and has a nearly spherical shape with sharp corners. Since it has a shape, the X-ray image conversion sheet of the present invention using this as a phosphor layer can obtain a phosphor layer having a higher phosphor filling factor than that using a conventional rare earth oxysulfide phosphor. X with improved photographic sensitivity and sharpness
A line image conversion sheet can be provided.

[0069]

[Brief description of the drawings]

FIG. 1 is a graph illustrating the correlation between the photographic sensitivity of an image conversion sheet of the present invention and the content of an alkali metal element in a phosphor used in a phosphor layer thereof.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G083 AA02 CC02 DD02 DD11 DD12 EE02 EE03 EE10 4H001 CA08 XA08 XA16 XA39 XA57 XA59 XA63 XA64 XA65 XA69 YA37 YA55

Claims (6)

[Claims] 1. The composition formula is (Ln _1-x , RE _x ) ₂ O
₂ S (Ln is Y, Gd, La and Lu
At least one of RE is Tb, Eu, Tm and Pr
And x is 1 × 10 ⁻³ ≦ x ≦
This is a number that satisfies the condition of ¹ × 10 ⁻¹ . ),
And a rare-earth oxysulfide phosphor containing an alkali metal element selected from at least one of cesium (Cs) and rubidium (Rb). 2. The method according to claim 1, wherein the content of the alkali metal element is 0.2.
The rare earth oxysulfide phosphor according to claim 1, wherein the phosphorous content is in a range of from 50 to 50 ppm. 3. A radiation image conversion screen in which a phosphor layer formed by dispersing a phosphor in a binder is formed on a support, wherein the phosphor has a composition formula (Ln _1-x , RE _x )
₂ O ₂ S (where Ln is at least one of Y, Gd, La and Lu, RE is Tb, Eu, Tm and P
r is at least one, and x is 1 × 10 ⁻³ ≦ x
≦ ¹ × 10 ⁻¹ ).
A radiation image conversion screen comprising a rare earth oxysulfide phosphor containing an alkali metal element selected from at least one of cesium (Cs) and rubidium (Rb). 4. The content of the alkali metal element is 0.2
The radiation image conversion screen according to claim 3, wherein the radiation image conversion screen is in a range of from about 50 ppm to about 50 ppm. 5. The method according to claim 1, wherein the content of the alkali metal element is 0.5.
The radiation image conversion screen according to claim 4, wherein the radiation image conversion screen is in a range of 10 to 10 ppm. 6. The method according to claim 6, wherein Ln is Gd, and RE is Tb.
The radiation image conversion screen according to any one of claims 3 to 5, wherein