JPS62110199A - Radiation intensifying screen and method of forming radiation picture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to radiation intensifying screens and methods of forming radiation images.

[Technical background of the invention] Radiation intensifying screens are used in various fields such as medical radiography such as X-ray photography for the purpose of medical diagnosis, and industrial radiography for the purpose of non-destructive testing of materials. In imaging, in order to improve the sensitivity of the imaging system, it is used by superimposing it closely on one or both sides of a radiographic film (for example, an X-ray photographic film).

This radiation intensifying screen basically consists of a support and a phosphor layer provided on one side of the support. Note that the surface of this phosphor layer opposite to the support (the surface not facing the support) is generally provided with a transparent protective film made of plastic film, etc. Protects the body layers from chemical alteration or physical impact. The protective film is usually attached to the phosphor layer by bonding a separately formed thin film using an adhesive.

The nine-body layer c' consists of a binder that contains and supports phosphor particles in a dispersed state, and these phosphor particles have the property of emitting high-intensity light when excited by radiation such as X-rays. It is something that you have. Therefore, the phosphor emits high-intensity light depending on the amount of radiation that passes through the subject, and the radiographic film placed in contact with the surface of the phosphor layer of the radiation-sensitizing screen can detect this luminescence. Since the radiation film is also sensitized by a relatively small amount of radiation, sufficient sensitization of the radiation film can be achieved with a relatively small radiation dose. Then, a radiation image of the subject is formed on the radiation film E.

2. Description of the Related Art It is desired that an imaging system consisting of a radiation intensifying screen and a radiographic film used in radiography has as high a sensitivity as possible in order to reduce the radiation dose to the subject as much as possible.

Further, it is desired that the obtained image has high image quality (!?#sharpness, graininess, etc.).

Traditionally, in order to increase the sensitivity of radiographic film,
An imaging system that uses a radiation film having a photographic emulsion layer on both sides of a support (double-sided film), and has radiation-sensitizing screens (front screen and pack screen) arranged on both sides of this film. (screen/film type) is used.

In such an imaging system, the fluorescence emitted from the radiation intensifying screen is not only absorbed directly by each emulsion layer of the adjacent radiographic film, but also transmitted through the film and reflected by the screen on the opposite side. This causes the light to be absorbed by the film and repeatedly reflected between the screens on both sides. Therefore, the emulsion layers on both sides of the film are not only exposed directly to the fluorescence from the screen, but also to this multiple reflected light (so-called crossover light). Crossover light spreads due to reflection by the screen and scattering when passing through the film, so sensitization of the film by crossover light tends to cause poor image quality (image blurring). There was a problem in that the image quality tended to be low.

A known method for removing this cross-over light that causes poor image quality is, for example, to color the double-sided film support with three to red colorants that absorb the fluorescence emitted from the screen. There is.

[Summary of the Invention] An object of the present invention is to provide a radiation intensifying screen that produces images with improved sharpness and a radiation image forming method using the screen.

Another object of the present invention is to provide a radiation intensifying screen that can produce images with improved sharpness without substantially reducing sensitivity or graininess, and a radiation image forming method using the screen. It is intended to be similar to LJ.

That is, the present invention provides a radiation-sensitizing screen having a support and a phosphor layer provided on the support L and made of a binder containing and supporting phosphor in a dispersed state, the screen including the phosphor layer. At least a part of the surface side portion is colored with a colorant whose average absorption rate in an emission region with a wavelength longer than the peak wavelength of the emission of the phosphor is higher than the average absorption rate in an emission region with a wavelength shorter than the peak wavelength. a radiation-sensitizing screen; and a method for forming a radiation image using a screen/film photographing system comprising a radiographic film and a radiation-sensitizing screen, wherein the radiation-sensitizing screen or the support and a phosphor layer made of a binder containing and supporting the phosphor provided on the support in a dispersed form, and at least a part of the screen surface side portion including the phosphor layer, The screen is colored with a colorant that has a higher average absorption rate in an emission region with a wavelength longer than the peak wavelength of the luminescence of the phosphor than in an emission region with a wavelength shorter than the peak wavelength. A radiation image forming method for:

As a result of research on the direction of image sharpness in a radiation image forming method using a screen film imaging system, the present inventor has discovered that a part of the radiation intensifying screen used in the imaging system is colored with a specific colorant. The inventors have discovered that by doing so, crossover light can be efficiently absorbed and removed, and images with excellent sharpness can be obtained, leading to the present invention.

- In general, silver halide, which is present in radiographic films and forms images, absorbs light of short wavelengths well. In the present invention, at least one of the phosphor layer, the adhesive layer, and the protective film of the radiation intensifying screen emits light in a wavelength region longer than the peak wavelength of the phosphor light emitted by the phosphor included in the phosphor layer. By coloring with a selectively absorbing colorant, the colored layer can actively absorb light in the long wavelength range, which is not directly absorbed by the film and is prone to multiple reflections. - On the other hand, light in a wavelength region shorter than the peak wavelength, which is easily absorbed by silver halide, is absorbed by the film and interferes with image formation. Thereby, crossover light can be efficiently removed, the sensitivity of the film to the crossover light can be reduced, and the sharpness of the resulting image can be improved.

In particular, phosphors that emit light in the near ultraviolet to 11 color regions (e.g. BaFBr:
When the screen is colored with a yellow colorant, the graininess is almost the same and the sharpness is improved, with almost no decrease in sensitivity. can be obtained.

[Configuration of the Invention] The radiation intensifying screen of the present invention can have the following configuration, for example. Note that FIGS. 1 to 3 are sectional views each schematically showing a configuration example of the radiation intensifying screen of the present invention.

(2) A screen consisting of a support l and a phosphor layer 2 provided on this L, and this phosphor layer is colored with a colorant (see Figure 1) 2) Support l, phosphor layer 2 and protection Il! 23 are laminated in order, and at least one of the phosphor layer and the protective film is colored with a colorant (see FIG. 2) 3)
Support 1, phosphor layer 2, adhesive layer 4 and support 2i 1t
! 23 are laminated in order, and at least one of the phosphor layer, adhesive layer, and protective film is colored with a colorant (see Figure 3). However, these three aspects This is an example of the structure of the radiation-sensitizing screen of the present invention, and the present invention is not limited to the embodiment described above. opposite side)
It is sufficient that at least one of the layers is colored with the coloring agent listed in F.

The radiation intensifying screen of the present invention can be manufactured, for example, by the method described below.

In the present invention, the coloring agent used to color the radiation-sensitizing screen has an average absorption rate in the emission region longer than the peak wavelength of the emission of the phosphor contained in the screen, which is longer than the peak wavelength. It is a colorant with a higher average absorption rate in the short wavelength emission region. For example, the colorant has a light absorption peak in a wavelength region longer than the light emission peak wavelength of the phosphor.

Therefore, the colorant will vary depending on the type of phosphor used in the screen. As described later, the phosphors used in the radiation intensifying screen of the present invention include:
Those that emit light in the near ultraviolet to visible region (blue region, green region, and red region) are preferable. Yellow to red colorants are used for such phosphors.

Examples of yellow to red colorants (dyes and pigments) preferably used in the present invention include various dyes such as azo dyes, acridine dyes, nolin dyes, thiazole dyes, and nitro dyes; and molybdenum orange, cadmium yellow, Yellow lead (Chrome xo-), Shinchrome-1
・Various pigments such as cadmium yellow and red lead can be mentioned.

r, 'Containment of coloring agent j1] Although it varies depending on the intended use of the radiation intensifying screen, the part of the screen to be colored, the type of coloring agent, etc. - Generally, the coloring agent is a dye. In some cases, it is selected from the range of 10:1 to 106:1 (phosphor dual colorant, heavy oxide ratio). In addition, when the colorant is a pigment, generally 1:10 to 10%: l
(phosphor: colorant, tunxing ratio).

The support used in the present invention can be arbitrarily selected from various materials known as materials for producing radiation intensifying screens. Examples of such materials include films of plastic substances such as cellulose acetate, polyester, polyethylene terephthalate, polyamide, polyimide, triacetate, polycarbonate, metal sheets such as aluminum foil, aluminum alloy foil, ordinary paper, /Helita paper, resin coated paper,
- Pigment paper containing pigments such as titanium oxide, paper sized with polyvinyl alcohol, etc. can be mentioned. However, in consideration of various properties as a radiation intensifying screen, a particularly preferred material for the support in the present invention is a plastic film.

This plastic film may be kneaded with a light-absorbing substance such as carbon black, or may be kneaded with a light-reflecting substance such as titanium oxide. Curved is a support suitable for a high sharpness type radiation intensifying screen, and the latter is a support suitable for a high sensitivity type radiation intensifying screen. In the present invention, from the viewpoint of sharpness, it is particularly preferable that the support is a plastic film kneaded with a light-absorbing substance such as carbon black.

In known radiation-sensitizing screens, in order to strengthen the bond between the support and the phosphor layer, or to improve the sensitivity or image quality of the radiation-sensitizing screen, a layer is added to the surface of the support on the side where the phosphor layer is provided. A polymer substance such as gelatin may be coated to form an adhesive layer, or a light-reflecting layer made of a light-reflecting substance such as titanium oxide, or a light-absorbing layer made of a light-absorbing substance such as carbon black. It is also being done to set up a In addition, in radiation intensifying screens used for industrial radiography whose purpose is non-destructive testing of substances, lead foil is placed on the surface of the support on the side where the phosphor layer is provided for the purpose of removing scattered radiation, etc. Metal foils such as lead alloy foils, tin foils, etc. are also provided.The support used in the present invention can also be provided with these various layers.

Furthermore, as described in JP-A-58-182599, in order to improve the sharpness, the surface of the support on which the phosphor layer is provided (the surface of the support on that side is provided with adhesive properties). 11 layers, light reflective layer.

If a light absorption layer or metal foil is provided, minute irregularities may be provided on the surface thereof.

A phosphor layer is formed on the support 1-.

The 5H phosphor layer is a layer consisting of a binder containing and supporting phosphor particles in a dispersed form.

Various types of phosphors are already known. Examples of phosphors that emit light in the near ultraviolet to visible region (blue region, green region, and red region) that are preferably used in the present invention include the following compounds. Tungstate-based phosphors (Ca W 04 , M g
W Oa, Cano, :pb, etc.), terbium-activated rare hepta-oxygen sulfide phosphor EY202S:Tb, Gd2O2
S: Tb, La2O2S: Tb, (Y, Gd) zo2s
:Tb, (Y , Gd) 2o2s :Tb , Tm, etc.], terbium-activated pore hexaphosphate phosphor (YPO4:
Tb, GdPO4Gb, LaPO4:Tb, etc.), terbium-activated rare oxyhalide phosphor (LaPO4:Tb, etc.)
OB r: Tb, La0Br: Tb%, Tm
, LaOCM: Tb, La0C1: Tb.

Tm, Gd0Br:Tb, Gd0CJl:Tb, etc.)
, thulium-activated lacustrine oxyhalide phosphor (L
aOBr: Tm, La0CJ1: Tm, etc.),
Sulfur M /< Lium-based phosphor [Ba5Oa: Pb, D
aSo4: Eu2°, (Ba, S r) soa
: Eu2゜, etc.], -valent europium activated alkaline earth metal phosphate phosphor [Ba, (PO4) 2:Eu
2°, (Ba, Sr)3 (PO4)2: Eu
2°, etc.], divalent europium-activated alkaline earth metal fluorohalide phosphor [BaFCM:Eu"", BaF
Br: Eu2°, BaFCfL: Eu2″″, Tb,
BaFBr:Eu”, Tb, BaF2・BaCf2*K
CfL: Eu2°, BaF2*BaC12-xBaS
O4・KC! ;L: Eu2°, (Ba, Mg)FzII
BaCl 2 ・KCu: Eu"", etc.], iodide-based phosphors (CsI:Na, CsI:T1.Nap, Kl:
Tl'3), sulfide-based phosphor [ZnS:Ag, (Zn,
Cd)S:Ag, (Zn,Cd)S:Cu, (Zn,
Cd)S: Cu, An, etc.], phosphoric acid haf=lambic phosphor (HfP207:Cu7), europium-activated rare earth oxysulfide phosphor [Y2O2S: Eu, Gd2O2S
:Eu, La2O2S:Eu, (Y, Gd)202
S: Eu, etc.], europium-activated rare earth oxide phosphor [Y2O3:Eu, Gd 20. :
Eu, La2O3:Eu, (Y, G
d) 203: Eu, europium-activated rarefied phosphate-based phosphor (YPOa: Eu, GdPO42Eu, LaPO, :Eu, etc.), niobium-activated rarefied vanadate-based phosphor [YVO4: Eu, GdVO4:
Eu, LaVO4: Eu, (Y, Gd) VOa
: Eu].

However, the phosphor used in the present invention is not limited to these, and any phosphor that emits light in the near-ultraviolet region or visible region when irradiated with radiation may be used.

Examples of binders for the phosphor layer include proteins such as gelatin,
Polysaccharides such as dextran, or natural polymeric substances such as gum arabic; and polyvinyl butyral, polyvinyl acetate, nitrocellulose, ethylcellulose, vinylidene chloride/vinyl chloride copolymer, polyalkyl (meth)acrylate, vinyl chloride/vinyl acetate Binders typified by synthetic polymeric materials such as copolymers, polyurethanes, cellulose acetate butyrate, polyvinyl alcohol, linear polyesters, etc. may be mentioned. Particularly preferred among such binders are nitrocellulose, linear polyester,
These are polyalkyl (meth)acrylates, mixtures of nitrocellulose and linear polyester, and mixtures of nitrocellulose and polyalkyl (meth)acrylates.

B. The light layer can be formed on the support, for example, by the following method.

First, add the phosphor described in L and a binder to a suitable solvent, and mix them thoroughly so that the phosphor particles are evenly distributed in the binder solution.
Prepare a q19 solution dispersed in

Examples of solvents for preparing coating solutions include lower alcohols such as methanol, ethanol, n-propanol, and n-butyl; chlorine H'X'F-containing hydrocarbons such as methylene chloride and ethylene chloride; benzene, Aromatic hydrocarbons such as toluene; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone; methyl acetate,
Esters of lower fatty acids and lower alcohols such as ethyl acetate and butyl acetate; ethers such as dioxane, ethylene glycol monoethyl ether, and ethylene glycol monomethyl ether; and mixtures thereof.

The mixing ratio of the binder and the phosphor in the coating solution varies depending on the characteristics of the intended radiation intensifying screen, the type of phosphor, etc., but generally the mixing ratio of the binder and the phosphor is l: It is selected from the range of 1 to 1:100 (ff! is the ratio), and is particularly preferably selected from the range of 1:8 to 1:40 (weight ratio).

The coating liquid contains a dispersant to improve the dispersibility of the phosphor particles in the coating liquid, and a dispersant to improve the bonding force between the binder and the phosphor particles in the phosphor layer after formation. Examples of dispersants used for such purposes include phthalic acid, stearic acid, caproic acid, lipophilic surfactants, etc., which may be mixed with various additives such as plasticizers to improve can be mentioned. Examples of plasticizers include phosphoric acid esters such as triphenyl phosphate, tricresyl phosphate, and diphenyl phosphate; heptathalic acid esters such as diethyl phthalate, dimeth+diethyl phthalate; ethyl phthalyl ethyl glycolate, butylphthalyl glycolate. Glycolic acid esters such as butyl; and polyesters of triethylene glycol and adipic acid,
Examples include polyesters of polyethylene glycol and aliphatic dibasic acids, such as polyesters of diethylene glycol and succinic acid.

Proceed as in Section L: A coating film containing the phosphor prepared in A and a binder is evenly applied to the surface of the support to form a coating film of the Coating/Ij solution. This coating operation is performed using a normal coating f-stage, such as a doctor blade or roll coater.
This can be done by using a knife coater or the like.

Then, the formed coating film is dried by gradually heating, thereby completing the formation of the phosphor layer on the support E. The thickness of the phosphor layer varies depending on the characteristics of the intended radiation intensifying screen, the type of phosphor, the mixing ratio of the binder and the phosphor, and is usually 20 pm to in. However, the thickness of this layer is preferably between 50 and 500 gm.

When the phosphor layer is colored with a coloring agent, the colored phosphor layer is provided by dispersing and containing the L coloring agent in the coating solution, and then coating the support with this coating solution and drying it. I can do it.

Note that the phosphor layer is not necessarily formed on the support as shown in L.
It is not necessary to directly apply the In liquid to form the phosphor layer; for example, after forming the phosphor layer by separately applying the coating liquid to a glass plate, metal plate, plastic sheet, etc. and drying it, it is possible to The support and the phosphor layer may be joined by pressing onto the support or by using an adhesive.

A protective film for physically and chemically protecting the phosphor layer may be provided on the surface of the phosphor layer opposite to the side in contact with the support.

The transparent protective film may be made of, for example, a cellulose conductor such as cellulose acetate or nitrocellulose; or a synthetic polymer material such as polymethyl methacrylate, polyvinyl alcohol, polyvinyl formal, polycarbonate, polyvinyl acetate, or vinyl chloride/vinyl acetate copolymer. The phosphor layer can be formed by coating the surface of the phosphor layer with a solution prepared by dissolving a transparent polymer substance such as the above in an appropriate solvent. Alternatively, it can also be formed by a method such as attaching a transparent thin film previously formed from polyethylene terephthalate, polyethylene, vinylidene chloride, polyamide, etc. to the surface of the phosphor layer using a suitable adhesive. For transparency, the film thickness of i5 nQ is preferably about 3 to 20 gm.

When coloring the protective film with a coloring agent, add 11 to the solution described in
Coloring by dispersing a colorant or by dispersing a colorant? By preparing a special pattern, a colored protective film can be provided.

In addition, when coloring the adhesive layer, i
By dispersing and containing a coloring agent, a 11-color adhesive layer can be interposed in the adhesive solution.

Next, the radiation image forming power method of the present invention will be explained with reference to the accompanying drawings, taking as an example the case of a combination of two double-sided films and twelve radiation intensifying screens. FIG. 4 is a diagram schematically explaining the radiation image forming method of the present invention.

In FIG. 4, the screen/film imaging system 8 consists of a radiographic film 10 placed in the center and one radiation intensifying screen 9.9° (front screen and back screen) placed on both sides of the radiographic film 10. The radiation film 10 consists of a support and photographic emulsion layers provided on both sides of the support. In addition, the intensifying screen 9.9°
Both consist of a support and a phosphor layer provided on one side of the support, and the phosphor layer is colored with a colorant. This photographing system 8 is installed so that the planes of the screen 9,9' and the film 10 are perpendicular to the direction of incidence of radiation.

After the radiation emitted from the radiation source 6 passes through the subject 7, a portion is absorbed by the front screen 9 and converted into fluorescence. Of this fluorescence, light in a wavelength region shorter than the peak wavelength sensitizes the emulsion layer of the adjacent film 10, but light in a longer wavelength region is relatively absorbed by the colored phosphor layer of the screen 9. Also, the front screen 9
The remaining radiation transmitted through the film 10 is absorbed by the bank screen 9° and converted into fluorescence. Similarly, light in the wavelength region shorter than the peak wavelength sensitizes the emulsion layer of the adjacent film IO, but light in the longer wavelength region is relatively absorbed by the colored phosphor layer at 9 degrees of the screen. be done.

A radiation image of the subject is formed on the double-sided film 10,
I! By developing the film after the shadow has been formed, a highly sharp visible image can be obtained on the film L.

In this way, by selectively absorbing and removing light in the long wavelength region where light absorption by silver halide is relatively small in the colored layer of the screen, the sensitization of the film due to crossover light is reduced and the image is easily scratched. Sharpness can be increased. In addition, light in the short wavelength region where light absorption by silver halide is relatively large is relatively difficult to be absorbed by the colored layer.

G% directly affects the exposure of the film, so the sensitivity of the screen is not very low. Further, the graininess of the obtained image is almost unchanged.

The radiographic film used in the L-ray image forming method basically consists of a support and a photographic emulsion layer. The photographic emulsion layer consists of a supporting binder such as gelatin containing dispersed silver halide. The radiographic film uses, for example, a plastic film such as polyethylene terephthalate as a support, and a photographic emulsion layer is provided on the L of the sheet. In the present invention, the support for the radiation film is preferably a plastic film mixed with a light-absorbing substance such as carbon black from the viewpoint of image sharpness. Further, from the viewpoint of sharpness, this support may be colored with the above-mentioned coloring agent. Furthermore, the radiation film does not have to be a double-sided film with photographic emulsion layers formed on both sides of the support, but may be a single-sided film with an emulsion layer formed on one side of the support.

Next, Examples and Comparative Examples of the present invention will be described.

However, each of these does not limit the present invention.

[Example 1] (1) '5J-value Eurobium-activated barium fluoride bromide phosphor (BaFBr:
Eu") ty) particles were dispersed in methyl ethyl ketone. To this dispersion, 80 tons of linear polyester resin (Byron Cloud 500, manufactured by Toyo Borin) and a degree of nitrification of 11.5% were added.
15 tons of nitrocellulose and incyanate (
Sumidur N-75, manufactured by Sumitomo Bayer Urethane) 5
Add a dose and add dye (Oil Yellow SS 5p
ecial, manufactured by Orient Chemical Co., Ltd., as a phosphor 100
After adding 3 mg to 1 g, stir and mix thoroughly using a propeller mixer to uniformly disperse the phosphor layer Y-, and the mixing ratio of the binder and the 911° nine bodies. is 1:
16 (small, gravity ratio) and viscosity of 25-30PS (25℃
) was prepared.

Next, carbon kneaded polyethylene terephthalate film (support, thickness: 2
Using a doctor blade, apply the coating solution evenly to L (50 lm). After coating, the support on which the coating film has been formed is placed in a dryer, and the temperature inside the dryer is adjusted to 25°C.
The temperature was gradually raised from 100°C to 100°C to dry the coating film. In this way, a layer thickness of about 150#Lm is deposited on the support.
A phosphor layer was formed.

Then, by placing and adhering a polyethylene terephthalate transparent film (thickness: 124 m, coated with polyester adhesive) on L of this phosphor layer with the adhesive layer side facing C, a transparent protective film is formed. A radiation intensifying screen consisting of a support, a phosphor layer and a transparent protective film was prepared.

(2) Radiography (formation of radiographic image) The obtained two radiation-sensitizing screens and a commercially available radiographic film are pressed together in a cassette to take a screen film as shown in 8 of Fig. 4 above. The system was installed, and x&Ia photography was performed in the arrangement shown in FIG.

After imaging, the radiation film is developed and an X-ray photograph is produced.

[Comparative Example 1] In the production of the radiation intensifying screen (1) in Example 1, except that Oil Yellow 3G (manufactured by Orient Chemical Co., Ltd.) was used as a dye at a ratio of 3.4 mg to 100 g of phosphor. A radiation intensifying screen consisting of a support, a phosphor layer and a transparent protective film was produced by carrying out the same treatment as in Example 1.

The dye here was added in order to make the sensitivity equivalent to that of the intensifying screen of Example 1 without changing the phosphor content and the layer thickness of the phosphor layer. The peak wavelength is the same as the peak wavelength of the luminescence of the phosphor, and although the luminescence of the phosphor is absorbed, the peak wavelength of the fluorescence emitted from the screen and its intensity distribution are not changed.

X
Radiography was performed to obtain an X-ray photograph on radiographic film L.

The light transmission spectrum of the coloring agent (Dye U) used in each of the above and the emission spectrum of each radiation intensifying screen are shown in FIGS. 5 and 6, respectively.

FIG. 5 is a graph showing the light transmission spectrum of the dye. In addition, in Fig. 5, the arrow (↑) indicates BaFBr:Eu
``It shows the peak position of the luminescence of the phosphor.

Nioil Yellow SS 5special (Example 1
)+7) Light Transmission Spectrum 2 Light Transmission Spectrum of Nioil Yellow 3G (Comparative Example 1) FIG. 6 is a graph showing the emission spectrum of the radiation intensifying screen.

l: Radiation Vj #3 sensitivity screen spectrum of Example 1 2: Emission spectrum of radiation m intensifying screen of Comparative Example 1 As shown in FIG. The absorption peak (transmission minimum) of 2) is the peak position of the light emission of the BaFBr:Eu” phosphor (
390 nm), and its transmission spectrum was almost identical to the emission spectrum of the phosphor, so it did not change the intensity distribution of the fluorescence emitted from the screen.・The absorption peak of Oil Yellow SS 5special (curve 1) used in the screen of Example 1 is on the longer wavelength side than the emission peak position of the phosphor, and is in the emission region on the longer wavelength side than 390 nm. It was clear that the average absorption rate of this dye was higher than the average absorption (A) in the emission region on the shorter wavelength side than 390 nm.

As is clear from FIG. 6, the emission intensity of the radiation intensifying screen of the present invention (Example 1) reached its maximum on the shorter wavelength side than the peak position (390 nm) of the emission of the BaFBr:Eu2'' phosphor. In other words, the average absorption rate of the screen was higher in the wavelength region longer than the emission peak position of the phosphor, and lower in the wavelength region shorter than that. The emission intensity reached its maximum at the emission peak position of the phosphor.

Next, each of the radiation intensifying screens and radiography described in L was evaluated by the image sharpness test, image graininess test, and sensitivity test described below.

(1) Image sharpness test Screen No. Film photographing system is irradiated with X-rays with a tube voltage of 80 KVp through a resolution chart to take an X-ray photograph, and the contrast transfer function (
CT F) is measured and divided into two spatial frequency cycles
It was expressed as a value of mm.

(2) Image graininess test Screen No. X-rays are transmitted through a water fan dome (thickness: 10 cm) and an aluminum plate (thickness = 10 mm) to a film imaging system at a density of 1.0 and a tube voltage of 80 KVp. was irradiated and an X-ray photograph was taken. This X-ray J°L film was processed at a temperature of 35°C for 90 seconds using a developer (RDIn, manufactured by Tomito Photo Film Hayashi) in an automatic processor (New RN, manufactured by Tomito Photo Film Co., Ltd.). The obtained film was measured using a microphotometer (aperture: 300
yLm×300 μm), and the RMS value was determined. This RMS value was used as a measure of graininess.

(3) Sensitivity test The sensitivity was measured by directly irradiating X&9 with a tube voltage of 80 KVp onto the screen/film photographing system without passing through the subject.

The results obtained are shown in Table 1.

Table 1 Sharpness (%) Graininess Relative sensitivity Example 1 43.9 1.28XIO-2105 Comparative Example 1 41.6 1.26X10-2 100
As is clear from the results summarized in Table 1, the radiation intensifying screen of the present invention and the radiation image forming method using the same (Example 1) are different from those of the radiation intensifying screen for comparison and the radiation image forming method using the same. Radiographic image forming method (Comparative example 1)
Compared to the previous model, images with high sharpness could be obtained with almost no reduction in graininess.

It should be noted that the intensifying screen of Comparative Example 1 had a dye added only for the purpose of making the sensitivity equivalent to that of the known intensifying screen.

4° Explanation of Width 1:n of the Drawings Figures 1 to 53 are sectional views showing an embodiment f9 of the radiation intensifying screen of the present invention.

FIG. 4 is a schematic diagram illustrating the radiation image forming method of the present invention.

FIG. 5 is a graph showing the light transmission spectrum of the dye.

FIG. 6 is a graph showing the emission spectrum of the radiation intensifying screen.

1: Support, 2: Phosphor layer, 3. Protective film, 4: Adhesive layer, 6: Radiation generator, 7: Subject, 8 Niscreen film photography system, 9.9': Radiation I? Radiographic Film Patent Applicant Tomito Photographic Film Co., Ltd. Agent Yasuo Yanagawa Figure 5 100 Wavelength (nm) Wave Fork (nm) Mountain IE e-';; Showa 61 2Jj a.

Claims (1)

[Claims] 1. A radiation intensifying screen having a support and a phosphor layer provided on the support and comprising a binder containing and supporting a phosphor in a dispersed state, in which the phosphor layer is At least a part of the surface side of the screen contains a colorant whose average absorption rate in a light emission region with a longer wavelength than the peak wavelength of light emission of the phosphor is higher than the average absorption rate in a light emission region with a shorter wavelength than the peak wavelength. A radiation intensifying screen characterized by being colored. 2. A patent characterized in that the radiation-sensitizing screen has a support, a phosphor layer, and a protective film in this order, and at least one of the phosphor layer and the protective film is colored with the colorant. A radiation intensifying screen according to claim 1. 3. The radiation intensifying screen has a support, a phosphor layer, an adhesive layer and a protective film in this order, and at least one of the phosphor layer, the adhesive layer and the protective film is colored with the colorant. A radiation intensifying screen according to claim 1, characterized in that: 4. The radiation intensifying screen according to claim 1, wherein the phosphor is a divalent europium-activated alkaline earth metal fluorohalide phosphor. 5. In a radiation image forming method using a screen/film imaging system consisting of a radiographic film and a radiation intensifying screen, the radiation intensifying screen disperses a support and a phosphor provided on the support. and a phosphor layer consisting of a supporting binder contained in the state, and at least a part of the screen surface side portion containing this phosphor layer is in a light emitting region with a wavelength longer than the peak wavelength of light emission of the phosphor. A radiation image forming method characterized in that the screen is colored with a coloring agent whose average absorption rate is higher than the average absorption rate in a light emission region having a wavelength shorter than the peak wavelength.