JPH0631891B2 - Fluorescent intensifying screen for radiography - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high-sensitivity fluorescent intensifying screen for radiography (hereinafter abbreviated as “intensifying screen”) for obtaining good photographic image quality.

(Background of the Invention) Intensifying screens are used in radiography in various fields such as medical radiography such as X-ray photography for medical diagnosis and industrial radiography for nondestructive inspection of substances. It is used in close contact with an X-ray film (hereinafter abbreviated as "film") in order to improve sensitivity. This intensifying screen is basically a support made of paper, plastic, etc.
The phosphor layer is provided on one surface of this support. The phosphor layer is formed by dispersing a phosphor that emits light with high brightness upon radiation excitation in a binder resin. The surface of the phosphor layer (the surface opposite to the support side) is generally a polyethylene terephthalate film, a cellulose acetate film, It is protected by a transparent protective film such as a methacrylate film and a nitrocellulose film.

In addition, the intensifying screen has a light absorbing layer between the support and the phosphor layer,
A device provided with a light reflecting layer or a metal foil is also known.

Further, some of the intensifying screens used in industrial radiography for the purpose of nondestructive inspection of a substance include a metal foil interposed between a support and a phosphor layer.

Intensifying screens are usually used in pairs for radiography. That is, a front side intensifying screen (radiation incident side) and a rear side intensifying screen are held in a film cassette, and a radiographic film of a double-sided emulsion is inserted between them to perform radiography.

Today, in medical diagnosis by radiography, a highly sensitive radiography system (combination of radiographic film and intensifying screen) is required to reduce the patient's exposure dose, but on the other hand, it is a photograph adapted to diagnosis in clinical photography. There is a demand for a radiography system capable of obtaining image quality (sharpness, graininess, contrast). In other words, radiography using an intensifying screen with excellent photo reproducibility of the microscopic part of the subject makes it possible to more accurately diagnose minute tissue changes of the patient in the medical radiological diagnosis area, and also metal structures. In the radiation non-destructive inspection of (1), it is possible to make the determination of cracks and the like, the detection of which is important, more accurate. It is possible to obtain intensifying screens with excellent photographic quality at the expense of photographic sensitivity. However, a decrease in photographic sensitivity causes an increase in patient dose in medical radiological diagnosis and a decrease in inspection efficiency in industrial nondestructive inspection, which is not preferable. That is, it has high sensitivity and enables improvement of diagnostic ability in medical radiography and improvement of discrimination in industrial radiography. An intensifying screen having good photographic image quality such as sharpness and graininess is required.

Calcium tungstate phosphor (CaWO ₄ ) has been widely used for intensifying screens, but the feature of the intensifying screen using CaWO ₄ phosphor is that good photographic image quality can be obtained. ₄ It depends on the characteristics peculiar to the phosphor. X
There are several phosphors that emit light with higher brightness than CaWO ₄ phosphors by line excitation, and for example, silver-activated zinc sulfide phosphor (ZnS: Ag) and the like are known. However, intensifying screens using these phosphors have poor photographic image quality under the shooting conditions normally used for medical diagnosis, and in particular have poor graininess as compared to intensifying screens using CaWO ₄ phosphor, and generally have low contrast. . Among the sharpness, graininess and contrast, the sharpness is
Compared with the other two, the dependence on the phosphor is smaller, and it can be improved by, for example, making the phosphor to be used into smaller particles or reducing the thickness of the phosphor layer. However, the graininess and contrast largely depend on the characteristics peculiar to the phosphor, and the graininess and contrast of the intensifying screen are basically determined by the phosphor used.

Recently, as a high-sensitivity intensifying screen, an intensifying screen using a phosphor having the following composition has been developed.

(Y _{0 ・ 998} , Tb _{0 ・ 002} ) ₂ O ₂ S (Y _{0 ・ 997} , Tb _{0 ・ 002} , Tm _{0 ・ 001} ) ₂ O ₂ S (Y _{0 ・ 598} , Gd _{0 ・ 4} , Tb _{0 ・ 002} ) ₂ O ₂ S (Y _{0 ・ 597} , Gd _{0 ・ 4} , Tb _{0 ・ 002} , Tm _{0 ・ 001} ) ₂ O ₂ S BaF ₂・ BaCl ₂・ KCl: Eu ²⁺ BaF ₂・ BaCl ₂・ 1.5KCl ・0.6BaSO ₄ : Eu ²⁺ KCl ・ 2BaCl ₂ : Eu ²⁺ BaFCl: Eu ²⁺ LaOBr: Tb LaOBr: Tb, Tm Gd ₂ O ₂ S: Tb However, graininess or contrast compared to intensifying screen using CaWO ₄ Has a bad drawback.

Further, JP-A-51-80190, JP-B-55-34400, and JP-A-56-339.
No. 5, 56-46514, intensifying screen in which two layers of different phosphors are stacked, a phosphor screen in which different phosphors are mixed as shown in JP-A-50-116168. Japanese Examined Japanese Patent Sho 55-3
The intensifying screen in which the particle size of the phosphor of 3560 is changed in the thickness direction of the phosphor layer, and a pair of intensifying screens sandwiching the film are different phosphors, as in JP-A-52-115685. A combination of intensifying screens, or a radiation conversion panel having a white pigment light reflection layer or a metal light reflection layer on the back surface as in JP-A-56-12600 and JP-A-56-11393 is known. Also, the technique of (1) cannot obtain good sharpness or graininess or contrast while maintaining high sensitivity.

Further, a metal foil is interposed between a support and a phosphor layer as used in an industrial radiographic intensifying screen, and a phosphor layer colored as in JP-A-54-70787 is used. Techniques such as a sensitive screen and an intensifying screen containing pigment particles that absorb the emission of a phosphor such as JP-B-58-2640 are known, but good image quality can be obtained, but sensitivity is lowered.

Further, the performance of the intensifying screen, that is, the photographic sensitivity and the photographic image quality of the intensifying screen is greatly influenced by the particle size of the phosphor used in the intensifying screen. Generally, the relationship between the intensifying screen performance and the particle size of the phosphor to be used improves the photographic image quality by using the fine particle phosphor, but on the other hand, it causes a decrease in the luminous efficiency of the phosphor, and further, the optical property in the phosphor layer. Loss increases and the photographic sensitivity is significantly reduced. On the contrary, the use of a large particle phosphor improves the photographic sensitivity, but on the other hand, because the phosphor particles are large and the light emission efficiency of the phosphor is good, scattered light is generated in the phosphor layer, which improves the photographic image quality. It will greatly reduce.

(Object of the Invention) It is an object of the present invention to provide an intensifying screen which has high sensitivity and gives good image quality in terms of sharpness, graininess and the like.

(Structure of the Invention) An object of the present invention is a radiographic fluorescent intensifying screen having a phosphor on a support, which further comprises heavy metal particles. Achieved by intensifying screens.

In the present invention, in the embodiment having a phosphor on the support and further heavy metal particles, (1) heavy metal particles (hereinafter referred to as specific metallic particles) are attached to the phosphor particles and dispersed in the binder. If present in the same coating layer, (2) if the specific metal particles and phosphor particles are present in the same coating layer dispersed in the binder, respectively, (3) specific metal particles and phosphor particles Are dispersed in the respective binders and are present in different coating layers (in this case, the coating layer in which the specific metallic particles are dispersed is either one of the coating layers in which the phosphor particles are dispersed). Alternatively, it may be provided on both sides.) (4) In the case where the coating layer of (1) or (2) and the coating layer in which the phosphor particles are dispersed are laminated on arbitrary sides of each other. , Etc. are listed as typical embodiments, and other composite embodiments of the above embodiments can be adopted as necessary. Further, the phosphor particles and the specific metallic particles may be two or more kinds in the same layer, or may be the same or different in different coating layers.

Further, if necessary, a protective film may be provided, and further a light reflecting layer, a light absorbing layer or other functional auxiliary layer may be provided.

In the present invention, a coating layer in which phosphor particles and / or specific metallic particles are dispersed and a composite layer thereof are collectively referred to as a sensitizing layer.

Examples of the phosphor according to the present invention include CaWO ₄ , ZnS: Ag, or the phosphor disclosed in JP-B-56-3395, and Y ₂ O.
₂ S: Tb, Gd ₂ O ₂ S: Tb, La ₂ O ₂ S: Tb, (Y, Gd) ₂ O ₂ S: Tb,
(Y, Gd) ₂ O ₂ S: Tb, Tm, Y ₂ O ₂ S: Eu, Gd ₂ O ₂ S: Eu, (Y, Gd) ₂ O
₂ S: Eu, Y ₂ O ₃ : Eu, Gd ₂ O ₃ : Eu, (Y, Gd) ₂ O ₃ : Eu, YVO ₄ :
Eu, YPO ₄ : Tb, GdPO ₄ : Tb, LaPO ₄ : Tb, YPO ₄ : Eu, LaOB
r: Tb, LaOBr: Tb, Tm, LaOCl: Tb, LaOCl: Tb, Tm, CdOB
r: Tb, GdOCl: Tb, CaWO ₄ , CaWO ₄ : Pb, BaSO ₄ : Pb, BaS
O ₄ : Eu ²⁺ , (Ba, Sr) SO ₄ : Eu ²⁺ , Ba ₃ (PO ₄ ) ₂ : Eu ²⁺ , (Ba, S
r) ₃ (PO ₄ ) ₂ : Eu ²⁺ , BaFCl: Eu ²⁺ , BaFBr: Eu ²⁺ , BaFCl:
Eu ²⁺ , Tb, BaFBr: Eu ²⁺ , Tb, BaF ₂ , BaCl ₂ , KCl: Eu ²⁺ , Ba
F ₂ , BaCl ₂ , BaSO ₄ , KCl: Eu ²⁺ , (Ba, Mg) F ₂ , BaCl ₂ , KCl: Eu
²⁺ , CsI: Na, CsI: Tl, NaI, (Zn, Cd) S: Ag, (Zn, Cd)
S: Cu, (Zn, Cd) S: Cu, Al, (Zn, Cd) S: Au, Al, HfP ₂ O ₇ : C
u, MgWO ₄ , KCl: Tl, CaS: Bi, SrS: Sm, Ce, ZnS: Au, A
l, ZnS: Cu, ZnS: Cu, Al, ZnS: Cu, Co, ZnS: Mn, ZnO:
_{Zn, BaSi 2 O 5: Pb} , Zn 2 SiO 4: Mn, Mg 2 SiO 4: Tb, BaSO 4:
Eu, MgB ₄ O ₇ : Tb, Ca ₃ (PO ₄ ) ₂ : Ce, Ca ₃ (PO ₄ ) ₄ : Ce, Mn, 3
_{Ca 3 (PO 4) 2:} Ca, (FCl) 2: Sb, Mn, Ba 3 (PO 4) 2: Eu, BaSrS
X of a phosphor having a composition such as O ₄ or a mixture thereof
Examples include line fluorescent substances.

The particle size of the phosphor is 0.5 to 12 μm, preferably 3 to 10 μm
Is. The content of the sensitizing layer is 49 to 98 wt% of the sensitizing layer weight.
%, Preferably 70 to 93 wt%, the coating amount is 15 to 200 mg / cm ² , 25
˜100 mg / cm ² , more preferably 40 to 50 mg / cm ² .

Next, as the specific metallic particles according to the present invention, first, as heavy metals, Pb, Pt, Ag, Au, Sn, Pd, Cd, In, Sb, Te, Mo,
Examples include Ir, Tl, and Ti.

The particle size of the specific metal particles is 0.05 to 50 μm, preferably 1/2 or less of the phosphor particle size, more preferably 0.1 to 3 μm, and the content is 0.5 to 50 wt% of the sensitizing layer weight, preferably 1 to
It is 25 wt%, more preferably 2 to 15 wt%.

Examples of the binder according to the present invention include proteins such as gelatin, polysaccharides such as dextran or gum arabic, polyvinyl butyral, polyvinyl acetate, nitrocellulose, nityl cellulose and vinylidene chloride.
Resins usually used for layer formation such as vinyl chloride copolymer, polymethylmethacrylate, vinyl chloride-vinyl acetate copolymer, polyurethane, cellulose acetate butyrate, polyvinyl alcohol and the like are used. As the solvent for the resin, acetone, ethyl acetate, butyl acetate, methylphthalic acid, phthalic anhydride, nitricene glycol or the like is used, and the addition amount is adjusted by the viscosity of the sensitizing layer coating solution. The content of the binder in the sensitizing layer is 1 to 50 wt% of the sensitizing layer weight, preferably 3 to 20 wt%, more preferably 5 to
It is 15 wt%.

As the support, those made of various polymeric materials, various materials such as glass, wool, cotton, paper, and metal can be used, but a flexible sheet or roll for handling as an information recording material can be used. Those that can be processed are preferable. From this point, for example, plastic films such as cellulose acetate film, polyester film, polyethylene terephthalate film, polyamide film, polyimide film, triacetate film, polycarbonate film, general paper and printing such as photographic base paper, coated paper or art paper Base paper, Paraita paper, resin coated paper, Belgian patent No. 784,
Particularly preferred are papers sized with polysaccharides and the like as described in Japanese Patent No. 615, pigment papers containing pigments such as titanium dioxide, and processed papers such as papers sized with polyvinyl alcohol and the like.

For coloring the support, for example, if it is black, a carbon black layer may be applied. It does not matter if it is colorless.
The thickness of the support is 100 to 500 μm, preferably 200 to 300 μm.

The sensitizing layer has a thickness of 10 to 1000 μm, preferably 50 to 500 μm.
m, more preferably 75 to 350 μm, most preferably 90 to 150
μm.

As a protective layer, nitrocellulose, ethyl cellulose,
Resins such as cellulose acetate, polyester, polyethylene terephthalate, polymethacrylate and polyvinyl butyral are used, and the thickness is 3 to 15 μm, preferably 5 to 10 μm.

In the present invention, as a method for containing the specific metallic particles in the sensitizing layer, (1) in the case of adhering to the surface of the phosphor particles, there is any one of the following methods.

For example, manufacturing method by electrostatic coating method (Japanese Patent Application No. 51-49436) Manufacturing method by suspension polymerization method (Japanese Patent Application No. 51-49437) Manufacturing method by copolymerization method (Japanese Patent Application No. 51-77649) Gelatin Manufacturing method using a mixture of gum arabic as an adhesive (Japanese Patent Application No. 51-80296) (2) When incorporated in a phosphor layer and / or a protective film and / or other layers For example, phosphor particles and specific metallic particles In a phosphor layer binding layer resin, for example, a manufacturing method in which the particles are uniformly dispersed by, for example, a ball mill. A specific metal particle is mixed in a resin for a protective film or a resin for other layers, and for example, a method in which the particles are uniformly dispersed by a ball mill. Etc.

The method for producing the intensifying screen of the present invention is produced by the generally used method for producing an intensifying screen except that it contains specific metallic particles. That is, an appropriate amount of the phosphor and / or specific metal particles and a binder resin such as nitrification cotton are mixed, and an appropriate amount of a solvent is added to the mixture to prepare a coating solution for the phosphor and / or specific metal particle having an optimum viscosity. Then, the phosphor and / or the coating liquid for the specific metal particles is coated on a support by a roll coater, a knife coater or the like and dried to form a sensitized layer.
This support may have an undercoat layer on one surface (the surface on which the sensitizing layer is provided) for the purpose of holding the sensitizing layer more closely. When the sensitizing layer is provided on the support, the sensitizing layer may be formed by directly applying a coating solution containing a phosphor and / or specific metal particles dispersed in a binder on the support. Alternatively, a separately prepared sensitizing layer may be adhered onto the support.

In the case of an intensifying screen having a structure having a light reflecting layer, a light absorbing layer or a metal foil between the support and the sensitizing layer, a light reflecting layer, a light absorbing layer or a metal foil is provided on the support in advance. ,
A phosphor and / or a coating liquid for specific metal particles is applied thereon and dried to form a sensitizing layer. When the sensitizing layer is composed of a plurality of layers, the first layer (the layer closest to the support) is first coated, and then the second and subsequent layers are sequentially coated by the same method.
In forming the sensitizing layer, a dispersant for improving the dispersibility of the phosphor and / or the specific metallic particles or dibutyl phthalate, methylphthalyl ethylene glycol or the like for increasing the flexibility of the intensifying screen to be obtained. You may add additives, such as a plasticizer, to the fluorescent substance and / or specific metallic particle coating liquid. Generally, many intensifying screens have a transparent protective film on the sensitizing layer for protecting the sensitizing layer, but the intensifying screen of the present invention is also preferably provided with a transparent protective film.

This protective film may be formed by directly applying a coating solution for protective film on the sensitizing layer, or a protective film separately formed in advance may be adhered on the sensitizing layer.

Sensitivity and image quality (sharpness, graininess, contrast) are important characteristics in radiography.

This sensitivity and image quality are generally contradictory characteristics, and it is difficult to improve both of them at the same time unless a special technique is used.

That is, in order to increase the sensitivity of the intensifying screen, it is known to use a highly sensitive phosphor, a phosphor having a large particle size, or a large amount of phosphor (a large layer thickness), The contrast, graininess, and sharpness are poor, respectively.

Further, the graininess of a radiograph includes the graininess of a photographic film, the graininess of an intensifying screen, and the graininess due to the statistical fluctuation of X-ray quanta, of which the graininess due to the statistical fluctuation occupies a large part.

Since the X-ray irradiation amount of the high-sensitivity intensifying screen is decreased, the incident X-ray quantum number is decreased, the statistical fluctuation is increased, and the graininess is deteriorated. In addition, a large amount of scattered X-rays generated in the subject in high X-ray tube voltage imaging of the chest of the human body, which is the most common in radiography, is apt to be felt, resulting in a decrease in contrast and a decrease in sharpness.

In the present invention, the method of dispersing the specific metallic particles in the vicinity of the phosphor is generally based on the fact that the heavy metal (compound) absorbs the scattered X-rays, and the X-rays that have passed through the object and go straight are the main components. It is considered to be a method of improving the sharpness of photographs by causing a phosphor to emit light, and also a method of causing a decrease in sensitivity due to absorption of scattered X-rays.

However, surprisingly, the sensitivity of the intensifying screen in which the specific metallic particles are dispersed in the vicinity of the phosphor as in the present invention is not lowered, and the graininess and the sharpness are improved.

(Example) Example-1 7% by weight of Pb particles having an average particle diameter of 0.5 µ was added to C having an average particle diameter of 5 µ.
Mixing 8 parts by weight of the phosphor with a heavy metal attached to the surface of aWO ₄ phosphor and 1 part by weight of nitrocellulose using a solvent (a mixture of acetone, ethyl acetate and butyl acetate in a weight ratio of 1: 1: 8). Then, a phosphor coating solution having a viscosity of 50 centistokes was prepared.

This phosphor coating solution was uniformly coated on a polyethylene terephthalate support having a carbon black light absorption layer of about 250 μm thickness using a knife coater so that the coating weight of the phosphor was about 45 mg / cm ^2, and dried at 50 ° C. And about 135
A sensitizing layer of μ was formed. Further, nitrocellulose was uniformly coated on the sensitized layer and dried to form a transparent protective film having a thickness of about 6μ. The intensifying screen thus obtained was designated as intensifying screen A.

Intensifying screen B was prepared in the same manner as intensifying screen A except that a CaWO ₄ phosphor having an average particle size of 6 μ was used. Further, under the same conditions as in the intensifying screen A except that the phosphor particle size and type are different, the intensifying screen C is formed by using the (Y, Gd) ₂ O ₂ S: Tb phosphor having an average particle size of 7 μ.
An intensifying screen D using Gd ₂ O ₂ S: Tb with an average particle size of 7μ, an intensifying screen E using BaFCl: Eu ²⁺ phosphor with an average particle size of 5μ, and a LaOBr: Tb phosphor with an average particle size of 6μ. With intensifying screen F having an average particle size of 10
Using ZnS: Ag phosphor of μ, intensifying screen G, L of average particle size 6μ
a ₂ O ₂ S: Tb phosphor and intensifying screen H
Intensifying screen I was prepared using the rSO ₄ phosphor. Of course, each of the phosphors in the intensifying screens B to I has the same average particle size as in the intensifying screen A.
7% by weight of 0.5μ Pb particles are attached to the surface of each phosphor. On the other hand, apart from these, except that the above phosphors that do not adhere Pb particles are used, the above A, B, C, D, E, F,
The conventional type intensifying screens prepared under exactly the same conditions as the G, H, and I intensifying screens are made to correspond to the above-mentioned order by a, b, and
C, d, e, f, g, h, and i intensifying screens were used.

The intensifying screens A, a, B, b, E, e, F, f, G, g,
Regular type X-ray film "Sakura X-Ray film type A" having sensitivity in the ultraviolet or blue light region is combined with each of I and i, and intensifying screens C, c, D, d, and
Each of H and h is combined with an ortho-type X-ray film "Sakura X-Ray film type AOG" which has sensitivity in the ultraviolet or blue light or green light region, and a tube voltage of 100 KVp,
X-ray photography is performed while controlling the X-ray irradiation amount so that the density of the photographic image after development is the same for each combination, and each exposed film is processed by a normal 90-second automatic processor (eg Konishi Roku Photo Development was performed with a VX-400 automatic processor manufactured by Kogyo Co., Ltd. to obtain a photographic image.

The sensitivity, sharpness and graininess of the obtained photographic image are as follows.
Shown in the table. The sensitivities in the table are conventional type intensifying screens (a, c, d, e, f, g, h,
i) and the relative sensitivity value with each film as 100, the sharpness is a modulation transfer function value (MTF value) at a spatial frequency of 2 lines / mm, and the graininess is R. at a photographic density of 1.0.
Shown as MS value.

As is clear from Table 1, the image obtained with the intensifying screen of the present invention is superior to the image obtained with the conventional type intensifying screen in any of sensitivity, sharpness and graininess. There is. That is, when the sensitivity is the same, the sharpness and graininess are excellent, and when the sensitivity is increased as in the case of the intensifying screens a and b, the sharpness and graininess are deteriorated. As can be seen from the comparison with the intensifying screen a, the same kind of phosphor has the same sharpness,
When it is granular, the sensitivity is high.

Example-2 1 part by weight of Pb particles having an average particle diameter of 1.0 μ and C having an average particle diameter of 4 μ
8 parts by weight of the aWO ₄ phosphor and 1 part by weight of nitrocellulose were mixed using a solvent (a mixed solution of acetone, ethyl acetate and butyl acetate) to prepare a phosphor coating solution having a viscosity of 50 centistokes. Intensifying screen J was prepared using this phosphor coating solution in exactly the same manner as in Example-1. Similarly, average particle size 6
Intensifying screen K was prepared in exactly the same manner as intensifying screen J except that the μ Gd ₂ O ₂ S: Tb phosphor was used. Similarly, B with an average particle size of 7μ
Intensifying screen L was prepared in the same manner as intensifying screen J except that the aSrSO ₄ phosphor was used.

On the other hand, except that Pb particles are not mixed separately, the above J,
The conventional type intensifying screens prepared under the same conditions as the K and L intensifying screens were designated as j for J, k for K, and l for L.

Further, 8 parts by weight of CaWO ₄ phosphor having an average particle diameter of 5 μ and 1 part by weight of nitrocellulose are mixed with a solvent (a mixed solution of acetone, ethyl acetate and butyl acetate) to apply a phosphor having a viscosity of 50 centistokes. The liquid was adjusted. This phosphor coating solution was uniformly applied on a polyethylene terephthalate support having a carbon black light absorption layer of about 250 μm thickness using a knife coater so that the phosphor coating weight would be about 50 mg / cm ^2, and dried at 50 ° C. Then, the sensitized layer was formed.
Furthermore, on this sensitized layer, nitrocellulose and average particle size
A liquid mixed with 0.5 parts by weight of 1.0 μ Pb particles (that is, 0.5 parts by weight with respect to 8 parts by weight of phosphor) was uniformly applied and dried to form a protective film having a thickness of about 10 μ. The intensifying screen thus obtained was designated as intensifying screen M. Similarly, intensifying screen N was prepared in the same manner as intensifying screen M except that Gd ₂ O ₂ S: Tb phosphor having an average particle diameter of 4 μ was used.

On the other hand, apart from this, a conventional type intensifying screen made under exactly the same conditions as the above M and N intensifying screens except that Pb particles were not mixed in the protective film was used. n intensifying screen.

Further, a liquid prepared by mixing 1.4 parts by weight of Pb particles having an average particle diameter of 3 μ (that is, 1.4 parts by weight with respect to 8 parts by weight of the phosphor) and nitrocellulose is supported by a polyethylene terephthalate support having a carbon black light absorption layer of about 250 μ thickness. It was applied evenly on the body to form an intermediate layer having a thickness of about 20μ. Further, on this intermediate layer, 8 parts by weight of CaWO ₄ phosphor having an average particle diameter of 5 μ and 1 part by weight of nitrocellulose were mixed using the same solvent as described above to prepare a phosphor coating solution having a viscosity of 50 centistokes. Then, the phosphor was uniformly coated on the intermediate layer with a knife coater so that the coating weight of the phosphor was about 40 mg / cm ^2, and dried at 50 ° C. to form a sensitized layer. Furthermore, nitrocellulose is uniformly coated on this sensitized layer, dried,
A transparent protective film having a thickness of about 5μ was formed. The intensifying screen thus obtained was named intensifying screen O. Similarly, the average particle size of 4μ
Intensifying screen P was prepared in the same manner as intensifying screen O except that the Gd ₂ O ₂ S: Tb phosphor was used.

On the other hand, apart from this, a conventional type intensifying screen made under the same conditions as the above O and P intensifying screens except that an intermediate layer is not used, is designated as O for O and p for P respectively. did.

Further, 8 parts by weight of CaWO ₄ phosphor having an average particle diameter of 5 μ and 1 part by weight of nitrocellulose were mixed using the same solvent as described above to prepare a phosphor coating solution having a viscosity of 50 centistokes. On a polyethylene terephthalate support having a carbon plaque light-absorbing layer, the phosphor was coated uniformly using a knife rotor so that the coating weight was about 25 mg / cm ² , to form a CaWO ₄ sensitized layer, and then the average particle size. 1 part by weight of 0.7μ Pb particles and the same average particle size as above 5
8 parts by weight of a CaWO ₄ phosphor of μ and 1 part by weight of nitrocellulose were mixed using the same solvent as described above to prepare a phosphor coating solution having a viscosity of 50 centistokes. _{4 The} coating weight of phosphor on the sensitized layer is about 25 mg / c
Use a knife coater to evenly apply the coating to m ²
After forming a CaWO ₄ sensitized layer containing particles, it was dried at 50 ° C.
Then, nitrocellulose was uniformly applied onto the Pb particle-mixed CaWO ₄ sensitized layer and dried to form a transparent protective film having a thickness of about 5 μm. The intensifying screen thus obtained was designated as intensifying screen Q. Similarly, intensifying screen R was prepared in the same manner as intensifying screen Q except that Gd ₂ O ₂ S: Tb phosphor having an average particle diameter of 6 μ was used.

On the other hand, apart from this, a conventional type intensifying screen made under exactly the same conditions as the above Q and R intensifying screens except that Pb particles were not used was changed to q intensifying for Q and r did.

Intensifying screens J, j, L, l, M, m, O, created in this way
Regular type X-ray film "Sakura X-Ray film type A" is combined with each of o, Q and q, and
Ortho-type X-ray film “Sakura X-Ray film type” on intensifying screens K, k, N, n, P, p, R and r
AOG "was combined, X-ray photography was performed at a tube voltage of 130 KVp in the same manner as in Example-1, and development processing was performed to obtain a photographic image. The sensitivity, sharpness and graininess of the obtained photographic image are shown in Table 2 below.

The sensitivities in the table are the conventional type intensifying screens j, k, l,
The relative sensitivity value, the sharpness, and the graininess, which are set to 100 in terms of the combined sensitivity of m, n, o, p, q, r and each of the above-mentioned films, are shown in the examples.
The same as 1.

As is clear from Table 2, the image obtained with the intensifying screen of the present invention is superior in sharpness and graininess without lowering the sensitivity as compared with the image obtained with the conventional type intensifying screen. There is.

Example-3 Example-1 except that 10% by weight of Sn particles of 0.7μ is used in place of 7% by weight of Pb particles having an average particle size of 0.5μ in Example-1.
In the same manner as in the intensifying screens A and D, intensifying screen S using CaWO ₄ as a phosphor and intensifying screen T using Gd ₂ O ₂ S: Tb were prepared. On the other hand, the above S except that Sn particles are not used separately.
Conventional type intensifying screens prepared under exactly the same conditions as the T and intensifying screens were designated as s and t intensifying screens, respectively.

In addition, in place of 1 part by weight of Pb particles having an average particle diameter of 1.0 μm in Example-2, Au particles were used, and intensifying screen J of Example-2 was used.
In the same manner as in K and K, an intensifying screen U using CaWO ₄ as a phosphor and an intensifying screen V using Gd ₂ O ₂ S: Tb were prepared. On the other hand, the conventional type intensifying screens prepared under the same conditions as the U and V intensifying screens were used as u and v intensifying screens, respectively, except that Au was not used.

Regular type X-ray film "Sakura X-Ray film type A" is combined with each of the intensifying screens S, s, U and u created in this way, and intensifying screens T, t, V and v are orthotype X respectively. Example 1 with a tube voltage of 80 KVp in combination with a line film "Sakura X-Ray film type AOG"
An X-ray photograph was taken in the same manner as in 1. and developed to obtain a photographic image. The sensitivity, sharpness, and graininess of the obtained photographic image are shown in Table 3 below.

The sensitivities in the table are conventional type intensifying screens t, u, v,
The relative sensitivity value, the sharpness, and the graininess, where the combined sensitivity of the film and each of the above-mentioned films is 100, are the same as in Example-1.

As is clear from Table 3, the image obtained with the intensifying screen according to the present invention is compared with the image obtained with the conventional type intensifying screen,
It can be seen that the sharpness and graininess are excellent without the sensitivity being lowered.

Claims (1)

[Claims] 1. A radiographic fluorescent intensifying screen having a phosphor on a support, which further comprises heavy metal particles.