JP3913342B2 - Radiation intensifying screen and radiation inspection equipment using it - Google Patents

Description

表１および図４から明らかなように、実施例１〜５による各Ｘ線増感紙は、いずれも比較例１のＸ線増感紙に比べて鮮鋭度が向上しており、その上で粒状性が維持されていることが分かる。
【００５３】
【発明の効果】
以上説明したように、本発明の放射線増感紙によれば、 2層構造の蛍光体層を構成する各蛍光体粒子の相対的な小粒径化による粒状性の向上効果を損なうことなく、鮮鋭度特性の低下を抑制することができる。従って、粒状性および鮮鋭度特性が共に優れる放射線増感紙を提供することが可能となる。
【図面の簡単な説明】
【図１】 本発明の放射線増感紙の一実施形態の構成を示す断面図である。
【図２】 本発明の放射線増感紙を用いた放射線レセプタの一構成例を示す断面図である。
【図３】 本発明の放射線増感紙を用いた放射線検査装置の一構成例を模式的に示す図である。
【図４】 2層構造の蛍光体層の全体としての蛍光体充填率と鮮鋭度特性との関係を示す図である。
【符号の説明】
１……支持体
２……蛍光体層
２ａ…第１の蛍光体層（大粒径蛍光体層）
２ｂ…第２の蛍光体層（小粒径蛍光体層）
３……保護膜
４……放射線増感紙[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radiation intensifying screen used for X-ray photography for medical diagnosis and the like and a radiation inspection apparatus using the same .
[0002]
[Prior art]
In X-ray imaging and the like used for medical diagnosis and industrial nondestructive inspection, a radiation film is usually used in combination with a radiation intensifying screen in order to improve the sensitivity of the imaging system. As a radiation intensifying screen used for X-ray photography or the like, a phosphor layer in which phosphor particles are dispersed in a binder is provided on a support made of paper, plastic, or the like, and a fluorescent layer is further formed thereon. In general, a thin protective film for protecting the body layer is formed.
[0003]
In addition, in order to improve the sharpness characteristics such as the sensitivity characteristics and image quality characteristics of radiation intensifying screens, two layers composed of two types of phosphor particles with different average particle diameters dispersed separately in a binder. Structured phosphor layers are also used. As a specific configuration of the phosphor layer having a two-layer structure, for example, a phosphor layer in which a large particle phosphor having an average particle diameter of about 7 to 20 μm and a phosphor having an average particle diameter of 4 μm or less are mixed on the protective film side. And a phosphor layer composed of a small particle phosphor having an average particle size of 4 μm or less is provided on the support side.
[0004]
By the way, in recent years, there has been an increasing demand for reducing the radiation exposure of a subject in medical diagnosis and the like. Therefore, in direct X-ray imaging, the exposure dose of the subject is reduced by using a radiation intensifying screen with increased sensitivity, for example. Such enhancement of the sensitivity of the radiation intensifying screen is carried out by using a phosphor having a high luminous efficiency such as Gd ₂ O ₂ S: Tb.
[0005]
Here, when a phosphor with high luminous efficiency is used, a decrease in graininess generally becomes a problem. Therefore, the graininess is improved by reducing the phosphor particle size. Similarly, in the phosphor layer having the two-layer structure, the phosphor particles constituting each phosphor layer are proceeding in a direction to relatively reduce the particle size. For example, it has been studied that the average particle size of the large particle phosphor is about 8 μm and the average particle size of the small particle phosphor is about 2 μm.
[0006]
However, reducing the particle size of the phosphor particles may lead to a reduction in sharpness. The identification ability of a subject in X-ray imaging is related to both the graininess and the sharpness, and the reduction in sharpness lowers the identification ability of a subject with a particularly low contrast. Even when using phosphors with high luminous efficiency, although a two-layer phosphor layer is effective in improving sensitivity characteristics and image quality characteristics, each phosphor layer is configured to improve graininess. When the phosphor particles to be made have a relatively small particle size, the sharpness is sacrificed.
[0007]
[Problems to be solved by the invention]
As mentioned above, increasing the sensitivity of radiation intensifying screens by using phosphors with high luminous efficiency is effective in reducing the exposure dose of the subject, and the two-layer structure of the phosphor layer is sensitive to sensitivity characteristics and image quality. Although effective in improving the properties, etc., in order to suppress the deterioration of graininess due to the phosphor with high luminous efficiency, the sharpness is improved when the phosphor particles constituting each phosphor layer are made relatively small in size. It will decline.
[0008]
For this reason, in particular, in a radiation intensifying screen having a phosphor layer with a two-layer structure using a phosphor with high luminous efficiency, the sharpness characteristics of each phosphor particle are reduced as the particle size is relatively reduced. It is a problem to suppress the decrease.
[0009]
The present invention has been made to cope with such problems. For example, when a phosphor layer having a two-layer structure using a phosphor with high luminous efficiency, the relative small particle size of each phosphor particle is used. An object of the present invention is to provide a radiation intensifying screen capable of suppressing a decrease in sharpness characteristics without impairing the effect of improving the graininess due to the conversion.
[0010]
[Means for Solving the Problems]
Radiographic intensifying screens of the present invention, a support is provided on the support, an average particle diameter of the first formed by dispersing the first phosphor particles in the range of 5 ~ 18 μ m in a binder a phosphor layer of two-layer structure and a second phosphor layer having an average particle size of the phosphor layer by dispersing the second phosphor particles in the range of 1 ~ 4 μ m in a binder, wherein the 2 a radiographic intensifying screen comprising a protective film provided on the phosphor layer of the layer structure, the weight ratio of the phosphor particles and the binder in each layer of the phosphor layer of the two-layer structure (binder / Phosphor ratio) is in the range of 1/100 to 1/20, respectively, and the phosphor particle filling ratio of the two-layered phosphor layer as a whole is in the range of 60 to 70%, and the protection said second firefly in the second phosphor layer filling rate of the first phosphor particles in the first phosphor layer formed on the film side is formed on the support side It is characterized by higher than the filling rate of the body particles. The radiation inspection apparatus of the present invention is characterized by using the radiation intensifying screen of the present invention.
[0011]
Radiographic intensifying screens of the present invention further among the phosphor layers of the two-layer structure, the weight ratio of the binder and the first phosphor particles in the first phosphor layer (binder / phosphor ratio ) together with a range of 1 / 100-3 / 100, 1/100 to weight ratio (binder / phosphor ratio) of the binder and the second phosphor particles in the second phosphor layer It is characterized by being in the range of 5/100.
[0013]
In the radiation intensifying screen of the present invention, the reduction in the sharpness due to the relatively small particle size of each phosphor particle constituting the two-layered phosphor layer is reduced, and the phosphor particles are filled as a whole phosphor layer. It is suppressed by increasing the rate. The sharpness characteristics of the radiation intensifying screen are greatly affected by the filling rate of the phosphor particles as a whole phosphor layer. Therefore, among the two-layered phosphor layers, the phosphor layer using a large particle phosphor is particularly important. The sharpness characteristic can be improved by reducing the binder / phosphor ratio (weight ratio) and increasing the filling rate of the phosphor particles as the entire phosphor layer.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, modes for carrying out the present invention will be described.
[0015]
FIG. 1 is a cross-sectional view showing the configuration of an embodiment of the radiation intensifying screen of the present invention. In the figure, reference numeral 1 denotes a support made of a plastic film, a nonwoven fabric or the like, and a phosphor layer 2 having a two-layer structure is provided on one surface of the support 1. A protective film 3 made of a plastic film, a plastic coating film, or the like is provided on the phosphor layer 2 having a two-layer structure, whereby a radiation intensifying screen 4, such as an X-ray intensifying screen for medical diagnosis, is provided. It is configured.
[0016]
The phosphor layer 2 having the two-layer structure described above includes a first phosphor layer 2a made of a large particle phosphor formed on the protective film 3 side and a second phosphor made of a small particle phosphor formed on the support 1 side. And a phosphor layer 2b. That is, the phosphor layer 2 having a two-layer structure is configured by separately dispersing two kinds of phosphor particles made of the same material phosphor and having different average particle diameters in a binder.
[0017]
The phosphor layer 2 having such a two-layer structure may be composed of a general phosphor such as CaWO _4, but a rare earth phosphor such as Gd ₂ O ₂ S: Tb or LaOBr: Tb having particularly high luminous efficiency. It is preferable to comprise. The radiation intensifying screen 4 of the present invention is particularly suitable when the rare earth phosphor having a high luminous efficiency as described above is used. That is, when using rare earth phosphors with high luminous efficiency, the decrease in graininess is suppressed by the relative particle size reduction of the phosphor particles, and the sharpness by the relative particle size reduction of the phosphor particles This reduction is suppressed by the configuration of the present invention described in detail later.
[0018]
The layers 2a and 2b constituting the phosphor layer 2 having a two-layer structure differ depending on the type of the phosphor used, but when the rare earth phosphor having a high luminous efficiency as described above is used, the following is shown. It is preferable to use phosphor particles each having an average particle size. That is, the large particle phosphor constituting the first phosphor layer 2a preferably has an average particle diameter in the range of 5 to 18 μm. If the average particle size of the large particle phosphor exceeds 18 μm, the graininess may be reduced. On the other hand, if the average particle size is less than 5 μm, the effect of improving the sensitivity characteristics and image quality characteristics due to the two-layer structure, etc. There is a possibility that it cannot be obtained sufficiently. In particular, it is desirable to use a large particle phosphor having an average particle diameter of about 8 μm for the first phosphor layer 2a.
[0019]
On the other hand, the small particle phosphor constituting the second phosphor layer 2b preferably has an average particle diameter in the range of 1 to 4 μm. If the average particle size of the small particle phosphor exceeds 4 μm, the graininess and sharpness characteristics may be deteriorated. On the other hand, phosphor particles having an average particle size of less than 1 μm are difficult to manufacture and have a high luminance. There is a high risk of causing a decrease or a decrease in the formability of the phosphor layer 2b. In particular, it is desirable to use a small particle phosphor having an average particle diameter of about 2 μm for the second phosphor layer 2b.
[0020]
In the first and second phosphor layers 2a and 2b, the weight ratio between the phosphor particles and the binder (binder / phosphor ratio) is set in the range of 1/100 to 1/20, respectively. The filling rate of the phosphor particles as a whole of the phosphor layer 2 is in the range of 60 to 70%. The sharpness of the radiation intensifying screen 4 having a two-layer structure, in particular, the sharpness of the radiation intensifying screen 4 in which the average particle diameter of the phosphor particles constituting each of the layers 2a and 2b is relatively small, is as a whole of the phosphor layer 2. The filling rate of the phosphor particles is affected.
[0021]
Therefore, by setting the phosphor particle filling ratio of the phosphor layer 2 as high as 60 to 70%, for example, the average particle diameter of the large particle phosphor constituting the first phosphor layer 2a is about 8 μm. The sharpness of the radiation intensifying screen 4 having a two-layer structure in which the average particle size of the small phosphors constituting the second phosphor layer 2b is relatively small, such as about 2 μm. Can be increased. In other words, for example, the granularity of the radiation intensifying screen 4 having a phosphor layer 2 having a two-layer structure using a phosphor having a high luminous efficiency is represented by the average particle diameter of the phosphor particles constituting the phosphor layers 2a and 2b. The sharpness can be increased by increasing the filling rate of the phosphor particles as the entire phosphor layer 2 while improving the relative smallness of each.
[0022]
When the filling rate of the phosphor particles as the whole phosphor layer 2 is less than 60%, the above-described sharpness improving effect cannot be sufficiently obtained. On the other hand, when focusing only on the sharpness characteristic of the radiation intensifying screen 4, it is desirable that the filling rate of the phosphor particles is higher, but it is difficult to produce a state where the filling rate exceeds 70%, On the contrary, there is a possibility that the graininess is lowered.
[0023]
In the present invention, in order to form the phosphor layer 2 having a two-layer structure in which the phosphor particle filling rate of the phosphor layer 2 as described above is in the range of 60 to 70%, each phosphor layer 2a is formed. The amount of the binder of 2b is reduced. Specifically, the binder / phosphor ratio (weight ratio) of each phosphor layer 2a, 2b is in the range of 1/100 to 1/20, respectively. When the binder / phosphor ratio of each of the phosphor layers 2a and 2b exceeds 1/20, the filling rate of the phosphor particles as the phosphor layer 2 as a whole cannot be satisfied. On the other hand, when the binder / phosphor ratio of each phosphor layer 2a, 2b is less than 1/100, the layer-forming property as the phosphor layer is impaired, and the retention property of the phosphor particles by the binder is lowered. .
[0024]
Here, when the filling rate of the phosphor particles as a whole of the phosphor layer 2 is set in the range of 60 to 70%, the amount of the binder in the second phosphor layer 2b made of the small particle phosphor is too much of the whole fluorescence. Since the body filling rate is not affected, it is preferable that the amount of the binder in the first phosphor layer 2a made of the large particle phosphor is particularly reduced. Further, the second phosphor layer 2b made of a small particle phosphor tends to deteriorate the layer-like film forming property when the amount of the binder is reduced too much. From this point of view, the amount of the binder in the first phosphor layer 2a is reduced. It is preferable to reduce and increase the filling rate of the phosphor particles as the entire phosphor layer 2.
[0025]
Specifically, the binder / phosphor ratio (weight ratio) of the first phosphor layer 2a made of a large particle phosphor is preferably in the range of 1/100 to 3/100. The binder / phosphor ratio (weight ratio) of the second phosphor layer 2b is preferably in the range of 1/100 to 5/100. By satisfying such a binder / phosphor ratio, the filling rate of the phosphor particles as the entire phosphor layer 2 can be efficiently increased.
[0026]
As described above, with respect to the phosphor layer 2 having a two-layer structure composed of two types of phosphor particles having different average particle diameters, radiation rate is increased by increasing the filling rate of the phosphor particles as the entire phosphor layer. The sharpness characteristics of the intensifying screen 4 can be improved. The effect of improving the sharpness characteristic is particularly effective in suppressing a decrease in graininess when using a rare earth phosphor or the like having a high luminous efficiency by reducing the relative particle size of the phosphor particles. That is, it is possible to suppress a decrease in sharpness due to a relatively small particle size of the phosphor particles by increasing the filling rate of the phosphor particles as the whole phosphor layer. As described above, in the radiation intensifying screen 4 having the phosphor layer 2 having the two-layer structure of the present invention, the decrease in the graininess when using the phosphor with high luminous efficiency is reduced by the relative small size of the phosphor particles. In addition to the suppression by the diameter, the reduction of the sharpness due to the relatively small particle size of the phosphor particles can be suppressed by improving the filling rate of the phosphor particles as the entire phosphor layer. Therefore, it is possible to provide the radiation intensifying screen 4 that is excellent in both the graininess and the sharpness characteristics.
[0027]
The radiation intensifying screen 4 of the above-described embodiment is produced as follows, for example. That is, first, the large particle phosphor is mixed with the binder within the above-described range, and an organic solvent is further added to prepare a large particle phosphor coating solution for the first phosphor layer 2a having an appropriate viscosity. On the other hand, the small particle phosphor is mixed with the binder within the above-described range, and an organic solvent is further added to prepare a small particle phosphor coating solution for the second phosphor layer 2b having an appropriate viscosity.
[0028]
Next, on the protective film 3 made of a transparent resin film such as polyethylene terephthalate, polyethylene, polyvinylidene chloride, polyamide, etc., a large particle phosphor coating solution for the first phosphor layer 2a is coated with a knife coater or a roll coater, Dry to form the first phosphor layer 2a. Next, a small particle phosphor coating solution for the second phosphor layer 2b is coated on the first phosphor layer 2a with a knife coater, a roll coater or the like, and dried to form the second phosphor layer 2b. To do.
[0029]
The binder used for preparing the phosphor coating liquid includes nitrified cotton, cellulose acetate, ethyl cellulose, polyvinyl butyral, cotton-like polyester, polyvinyl acetate, vinylidene chloride-vinyl chloride copolymer, vinyl chloride-vinyl acetate copolymer, polyalkyl ( Examples conventionally used are (meth) acrylate, polycarbonate, polyurethane, cellulose acetate butyrate, polyvinyl alcohol and the like. As the organic solvent, for example, ethanol, methyl ethyl ether, butyl acetate, ethyl acetate, ethyl ether, xylene and the like are used. In addition, a dispersing agent such as phthalic acid and stearic acid and a plasticizer such as triphenyl phosphate and diethyl phthalate can be added to the phosphor coating liquid as necessary.
[0030]
And the target radiation intensifying screen 4 is obtained by laminating | stacking the support body 1 on the fluorescent substance layer 2 of the 2 layer structure mentioned above, for example. As the support 1, for example, a resin such as polyester such as cellulose acetate, cellulose propionate, cellulose acetate butyrate, polyethylene terephthalate, polystyrene, polymethyl methacrylate, polyamide, polyimide, vinyl chloride-vinyl acetate copolymer, polycarbonate is formed into a film. Can be used.
[0031]
The protective film 3 is made by dissolving a cellulose derivative such as cellulose acetate, nitrocellulose, or cellulose acetate butyrate, a resin such as polyvinyl chloride, polyvinyl acetate, polycarbonate, polyvinyl butyral, polymethyl methacrylate, polyvinyl formal, or polyurethane in a solvent. Alternatively, it may be formed by applying and drying a protective film coating solution having an appropriate viscosity. In this case, each phosphor coating solution may be coated on the support 1, and a protective film coating solution may be coated thereon.
[0032]
Some intensifying screens have a structure in which a light reflecting layer, a light absorbing layer, a metal foil layer, and the like are provided between the support 1 and the phosphor layer 2. A light reflecting layer, a light absorbing layer, a metal foil layer or the like may be formed on the body 1 and laminated on the phosphor layer 2 having the two-layer structure described above.
[0033]
The radiation intensifying screen 4 of the above-described embodiment is used for radiation imaging such as X-ray imaging as a radiation receptor 5 as shown in FIG. The radiation receptor shown in FIG. 2 has a radiation film 6 such as an X-ray film sandwiched between two radiation intensifying screens 4 (a front intensifying screen F and a back intensifying screen B), and is accommodated in a cassette 7 in this state. Yes. Such a radiation receptor 5 is used by being inserted into a radiation inspection apparatus 8 as shown in FIG. A radiation inspection apparatus 8 shown in FIG. 3 includes a radiation source 9 and an imaging table 11 arranged via a subject 10 such as a subject. The radiation receptor 5 is used by being inserted from the side surface of the imaging table 11. At this time, the radiation receptor 5 is inserted so that the front intensifying screen F is positioned on the subject 10 side.
[0034]
When the radiation inspection apparatus 8 using the radiation receptor 5 configured using the radiation intensifying screen 4 of this embodiment reduces the X-ray exposure dose to the subject by increasing the sensitivity of the imaging system In this case, a good discrimination ability can be obtained. That is, for example, when used for medical X-ray imaging, it is possible to obtain a good diagnostic ability while reducing the X-ray exposure dose to the subject.
[0035]
【Example】
Next, specific examples of the present invention will be described.
[0036]
Example 1
First, polyvinyl butyral is added to a Gd ₂ O ₂ S: Tb phosphor powder having an average particle size of 8 μm so that the binder / phosphor weight ratio is 1/100, and an appropriate amount of butyl acetate as an organic solvent is added. Were added and thoroughly mixed to prepare a large particle phosphor coating solution. Similarly, polyvinyl butyral is added to a Gd ₂ O ₂ S: Tb phosphor powder having an average particle diameter of 2 μm so that the weight ratio of the binder / phosphor is 1/100, and an appropriate amount of acetic acid is added as an organic solvent. Butyl was added and mixed well to prepare a small particle phosphor coating solution.
[0037]
Then, on the protective film made of a polyethylene terephthalate film having a thickness of 9 μm, first, a large particle phosphor coating solution was uniformly applied with a knife coater and dried to form a first phosphor layer made of a large particle phosphor. Next, a small particle phosphor coating solution was uniformly coated on the first phosphor layer with a knife coater and dried to form a second phosphor layer made of a small particle phosphor. The phosphor weight ratio between the first phosphor layer and the second phosphor layer was 40:60 (= large particle phosphor: small particle phosphor).
[0038]
The phosphor filling factor of the two-layered phosphor layer thus obtained was determined from the following equation.
[0039]
P = V _P / V = W / V / ρ _P
(Wherein P is the phosphor filling rate of the phosphor layer, V _P is the volume of the phosphor, V is the volume of the phosphor layer (excluding the protective film and the support), W is the weight of the phosphor, and ρ _P is As a result, the phosphor filling rate of the first phosphor layer (large particle phosphor layer) is 70% and the phosphor filling of the second phosphor layer (small particle phosphor layer). The rate was 63%, and the phosphor filling factor of the phosphor layer as a whole was 66%.
[0040]
Thereafter, a support made of a polyethylene terephthalate film having a thickness of 250 μm was adhered onto the phosphor layer having the two-layer structure described above to produce a target X-ray intensifying screen. This X-ray intensifying screen was subjected to the characteristic evaluation described later.
[0041]
Example 2
In the X-ray intensifying screen of Example 1, the binder / phosphor weight ratio of the first phosphor layer (large particle phosphor layer) and the second phosphor layer (small particle phosphor layer) was 3/100. Except that, an X-ray intensifying screen was prepared in the same manner as in Example 1 and subjected to the characteristic evaluation described later.
[0042]
The phosphor filling rate of the X-ray intensifying screen according to Example 2 was determined in the same manner as in Example 1. First, the phosphor filling rate of the first phosphor layer (large particle phosphor layer) was 66%, The phosphor filling rate of the second phosphor layer (small particle phosphor layer) was 61%, and the phosphor filling rate of the entire phosphor layer was 64%.
[0043]
Example 3
In the X-ray intensifying screen of Example 1, the binder / phosphor weight ratio of the first phosphor layer (large particle phosphor layer) and the second phosphor layer (small particle phosphor layer) is 5/100. Except that, an X-ray intensifying screen was prepared in the same manner as in Example 1 and subjected to the characteristic evaluation described later.
[0044]
The phosphor filling rate of the X-ray intensifying screen according to Example 3 was determined in the same manner as in Example 1. First, the phosphor filling rate of the first phosphor layer (large particle phosphor layer) was 63%, The phosphor filling rate of the second phosphor layer (small particle phosphor layer) was 59%, and the phosphor filling rate of the entire phosphor layer was 61%.
[0045]
Example 4
In the X-ray intensifying screen of Example 1, the binder / phosphor weight ratio of the first phosphor layer (large particle phosphor layer) is 3/100, and the second phosphor layer (small particle phosphor layer). An X-ray intensifying screen was prepared in the same manner as in Example 1 except that the binder / phosphor weight ratio of 5/100 was 5/100, and subjected to the characteristic evaluation described later.
[0046]
The phosphor filling rate of the X-ray intensifying screen according to Example 4 was determined in the same manner as in Example 1. First, the phosphor filling rate of the first phosphor layer (large particle phosphor layer) was 66%. The phosphor filling rate of the second phosphor layer (small particle phosphor layer) was 59%, and the phosphor filling rate of the entire phosphor layer was 63%.
[0047]
Example 5
In the X-ray intensifying screen of Example 1, the binder / phosphor weight ratio of the first phosphor layer (large particle phosphor layer) is 1/100, and the second phosphor layer (small particle phosphor layer). An X-ray intensifying screen was prepared in the same manner as in Example 1 except that the weight ratio of the binder / phosphor was 4/100.
[0048]
The phosphor filling rate of the X-ray intensifying screen according to Example 5 was measured in the same manner as in Example 1. First, the phosphor filling rate of the first phosphor layer (large particle phosphor layer) was 70%, The phosphor filling rate of the second phosphor layer (small particle phosphor layer) was 59%, and the phosphor filling rate of the entire phosphor layer was 63%.
[0049]
Comparative Example 1
In the X-ray intensifying screen of Example 1, the binder / phosphor weight ratio of the first phosphor layer (large particle phosphor layer) and the second phosphor layer (small particle phosphor layer) is 6/100. Except that, an X-ray intensifying screen was prepared in the same manner as in Example 1 and subjected to the characteristic evaluation described later.
[0050]
The phosphor filling rate of the X-ray intensifying screen according to Comparative Example 1 was measured in the same manner as in Example 1. First, the phosphor filling rate of the first phosphor layer (large particle phosphor layer) was 55%. The phosphor filling rate of the second phosphor layer (small particle phosphor layer) was 53%, and the phosphor filling rate of the entire phosphor layer was 54%.
[0051]
About each X-ray intensifying screen by Examples 1-5 mentioned above and comparative example 1, the sensitivity, sharpness, and granularity were measured and evaluated using an orthotype film (Konica company make, SR-G). The results are shown in Table 1 and FIG. The photographic performance of the X-ray intensifying screen is the photographic sensitivity, sharpness, and graininess when photographed with X-rays with a tube voltage of 120 kV through a 100 mm thick water phantom. Relative value when line intensifying screen is 100. The sharpness is a relative value when the MTF value at a spatial frequency of 2 lines / mm is obtained and the MTF value of the X-ray intensifying screen of Comparative Example 1 at the spatial frequency is 100. The graininess is a relative RMS value at a photographic density of 1.0 and a spatial frequency of 3.12 lines / mm.
[0052]
[Table 1]

As apparent from Table 1 and FIG. 4, each of the X-ray intensifying screens according to Examples 1 to 5 has improved sharpness as compared with the X-ray intensifying screen of Comparative Example 1, and on that, It can be seen that the graininess is maintained.
[0053]
【The invention's effect】
As described above, according to the radiation intensifying screen of the present invention, without impairing the effect of improving the graininess due to the relatively small particle size of each phosphor particle constituting the phosphor layer having a two-layer structure, A reduction in sharpness characteristics can be suppressed. Therefore, it is possible to provide a radiation intensifying screen having both excellent graininess and sharpness characteristics.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a configuration of an embodiment of a radiation intensifying screen of the present invention.
FIG. 2 is a cross-sectional view showing a structural example of a radiation receptor using the radiation intensifying screen of the present invention.
FIG. 3 is a diagram schematically showing a configuration example of a radiation inspection apparatus using the radiation intensifying screen of the present invention.
FIG. 4 is a diagram showing a relationship between a phosphor filling factor and a sharpness characteristic as a whole of a phosphor layer having a two-layer structure.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Support body 2 ... Phosphor layer 2a ... 1st phosphor layer (large particle size phosphor layer)
2b ... Second phosphor layer (small particle size phosphor layer)
3 ... Protective film 4 ... Radio screen

Claims (4)

A support provided on the support, an average particle diameter of the first phosphor layer having an average particle diameter was dispersed first phosphor particles in the range of 5 ~ 18 μ m in the binder 1 a second phosphor layer and the phosphor layer of two layer structure having a dispersed with ~ 4 mu m second phosphor particles ranging in a binder, provided on the phosphor layer of the two-layer structure A radiation intensifying screen having a protective film formed thereon ,
The weight ratio (binder / phosphor ratio) between the phosphor particles and the binder in each layer of the two-layer phosphor layer is in the range of 1/100 to 1/20, and the two-layer structure The filling rate of the phosphor particles as a whole of the phosphor layer is in a range of 60 to 70%, and the filling rate of the first phosphor particles in the first phosphor layer formed on the protective film side is A radiation intensifying screen characterized by being higher than a filling rate of the second phosphor particles in the second phosphor layer formed on the support side. The radiation intensifying screen according to claim 1,
Of the two-layered phosphor layer, the weight ratio (binder / phosphor ratio) of the first phosphor particles to the binder in the first phosphor layer is 1/100 to 3/100. And the weight ratio (binder / phosphor ratio) between the second phosphor particles and the binder in the second phosphor layer is in the range of 1/100 to 5/100. Radiation intensifying screen. In the radiation intensifying screen according to claim 1 or 2 ,
The radiation intensifying screen, wherein the phosphor particles are made of a Gd ₂ O ₂ S: Tb phosphor. A radiation inspection apparatus using the radiation intensifying screen according to any one of claims 1 to 3 .

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