JPH0452920B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a radiation image conversion panel used in a radiation image conversion method that utilizes a photostimulable phosphor. More specifically, the present invention relates to a radiation image storage panel comprising a support, a phosphor layer made of a stimulable phosphor, an adhesive layer, and a protective film in this order.

[Technical Background of the Invention and Prior Art] As a method for obtaining radiation images as images, the so-called radiography method has conventionally used a combination of a radiographic film having an emulsion layer made of a silver salt photosensitive material and an intensifying screen. It's being used. Recently, a radiation image conversion method using a stimulable phosphor, as described in Japanese Patent Application Laid-open No. 55-12145, has been attracting attention as an alternative to the above-mentioned radiographic method. Summer. This radiation image conversion method uses a radiation image conversion panel (stimulable phosphor sheet) containing a stimulable phosphor. Accumulated in the stimulable phosphor by absorbing it into the stimulable phosphor and then exciting the stimulable phosphor with electromagnetic waves (excitation light) such as visible light or infrared rays in a time-series manner. Radiation energy is emitted as fluorescence (stimulated luminescence), this fluorescence is read photoelectrically to obtain an electrical signal, and the obtained electrical signal is converted into an image.

The above-mentioned radiation image conversion method has the advantage that a radiation image rich in information can be obtained with a much lower exposure dose than conventional radiography methods. Therefore, this radiation image conversion method has a very high utility value especially in direct medical radiography such as X-ray photography for the purpose of medical diagnosis.

The radiation image conversion panel used in the above radiation image conversion method has a basic structure consisting of a support and a phosphor layer provided on one side of the support. Note that a transparent protective film is generally provided on the surface of the phosphor layer opposite to the support (the surface not facing the support) to protect the phosphor layer from chemical deterioration or Protects from physical impact. The protective film is usually attached to the phosphor layer by adhering a separately formed thin film using an adhesive.

The phosphor layer consists of a stimulable phosphor and a binder that contains and supports the stimulable phosphor in a dispersed state. After absorbing radiation such as X-rays, the stimulable phosphor absorbs visible light and It has the property of emitting light (stimulated luminescence) when irradiated with electromagnetic waves (excitation light) such as infrared rays. Therefore, the radiation transmitted through the subject or emitted from the subject is absorbed by the phosphor layer of the radiation conversion panel in proportion to the amount of radiation, and a radiation image of the subject or subject is displayed on the radiation image conversion panel. is formed as an accumulated image of radiation energy. This accumulated image can be emitted as stimulated luminescence by time-series excitation with the electromagnetic waves mentioned above, and by reading this stimulated luminescence photoelectrically and converting it into an electrical signal, the accumulated image of radiation energy can be imaged. It becomes possible to convert into

The radiation image conversion method described above is a very advantageous image forming method as described above, but the radiation image conversion panel used in this method also has image quality ( sharpness,
It is desirable that the image be able to provide an image with good graininess (graininess, etc.).

In the radiation image conversion method, the sharpness of the image is determined not by the spread of stimulated luminescence light emitted from the phosphor of the radiation image conversion panel, but by the spread of excitation light within the panel. because,
The image of the radiation energy accumulated in the radiation image conversion panel is taken out in a time-series manner, so the stimulated luminescence due to excitation light irradiated to the panel within a certain time is the fluorescence caused by excitation light irradiated within that time. However, if the excitation light spreads due to scattering within the panel and excites phosphor particles existing outside the irradiation target phosphor particle group, the irradiation target This is because output from a wider area than the phosphor particle group is recorded.

As a technique for improving the sharpness of a radiation image storage panel, a method has been proposed in which the panel is colored with a colorant that absorbs excitation light. A radiation image conversion panel colored with this colorant is disclosed in, for example, Japanese Patent Application Laid-Open No. 57-96300. Regarding the image conversion panel, a panel in which at least one of the panels is colored is described.

When applying the above radiation image conversion method particularly to medical radiography, it is necessary to reduce the exposure dose to the human body and obtain more information, so the radiation image conversion panel used in the method has as high a sensitivity as possible. It is also desirable that the image quality be as good as possible. For these reasons, it is desired to develop a technique that further improves the sensitivity and image quality of radiation image conversion panels.

[Object of the Invention] An object of the present invention is to provide a radiation image conversion panel with improved image sharpness.

Another object of the present invention is to provide a radiation image conversion panel with improved image sharpness and sensitivity.

The above object is to provide a radiation image conversion panel having a support, a phosphor layer comprising a supporting binder containing a stimulable phosphor in a dispersed state, an adhesive layer, and a protective film in this order. can be achieved by the radiation image conversion panel of the present invention, which is colored with a colorant that absorbs at least a part of the excitation light for causing the stimulable phosphor to stimulate luminescence. .

[Effects of the Invention] The present invention improves the sharpness of images obtained by coloring the adhesive layer provided between the phosphor layer and the protective film of the radiation image conversion panel. Further, the present invention provides a radiation image conversion panel that provides images with better sharpness than known radiation image conversion panels when comparing panels having the same sensitivity.

As mentioned above, a protective film is generally adhered to the radiation image conversion panel, and this protective film is usually attached by adhering a separately formed transparent thin film onto the phosphor layer using an adhesive. It is carried out by According to the inventor's study, a thin adhesive layer (several μm to several tens of μm) is colored with a colorant that selectively absorbs excitation light for stimulating the phosphor. It has been found that the sharpness of the resulting image can be improved by efficiently absorbing the excitation light spread in the protective film by the colored adhesive layer.

In addition, when a thin adhesive layer is colored as described above, sharpness can be improved without significantly reducing sensitivity compared to when a thicker layer such as a phosphor layer is colored. It turns out that it can be improved. In other words, by coloring a thin adhesive layer, absorption of stimulated light in the colored layer is minimized, and excitation light that spreads in the protective film due to scattering etc. is reduced as much as possible. It can be absorbed efficiently.

Therefore, when the radiation image conversion panel of the present invention is made to have the same sensitivity as a known radiation conversion panel in which the phosphor layer is colored, the layer thickness of the phosphor layer can be made thinner. It is possible to further improve sharpness when comparing sensitivity. In other words, this means that the sensitivity can be further improved when comparing the same sharpness.

[Structure of the Invention] The radiation image conversion panel of the present invention having the preferable characteristics as described above can be manufactured, for example, by the method described below.

The support used in the present invention can be arbitrarily selected from various materials used as supports for intensifying screens in conventional radiography methods or materials known as supports for radiation image conversion panels. . Examples of such materials include films of plastic materials such as cellulose acetate, polyester, polyethylene terephthalate, polyamide, polyimide, triacetate, polycarbonate, metal sheets such as aluminum foil, aluminum alloy foil, regular paper, baryta paper, resins, etc. Examples include coated paper, pigment paper containing pigments such as titanium dioxide, and paper sized with polyvinyl alcohol. However, when considering the characteristics and handling of the radiation image conversion panel as an information recording material,
A particularly preferred material for the support in the present invention is 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 dioxide.
The former is a support suitable for a high sharpness type radiation image conversion panel, and the latter is a support suitable for a high sensitivity type radiation image conversion panel.

In known radiation image conversion panels, a phosphor layer is provided in order to strengthen the bond between the support and the phosphor layer, or to improve the sensitivity or image quality (sharpness, granularity) of the radiation image conversion panel. A polymeric substance such as gelatin is coated on the surface of the support on the side to be coated to form an adhesion imparting layer, or a light reflective layer made of a light reflective material such as titanium dioxide, or a light absorbing material such as carbon black. Providing a light absorption layer is also practiced. The support used in the present invention can also be provided with these various layers, and their configurations can be arbitrarily selected depending on the purpose, use, etc. of the desired radiation image storage panel.

Furthermore, as described in Japanese Patent Application Laid-Open No. 58-200200, in order to improve the sharpness of the obtained image, the surface of the support on the phosphor layer side (the surface of the support on the phosphor layer side) When an adhesion-imparting layer, a light-reflecting layer, a light-absorbing layer, etc. are provided, fine irregularities may be uniformly formed on the surface (meaning the surface thereof).

Next, a phosphor layer is formed on the support.
The phosphor layer is basically a layer consisting of a binder containing and supporting particles of stimulable phosphor in a dispersed state.

As mentioned above, a stimulable phosphor is a phosphor that exhibits stimulated luminescence when irradiated with radiation and then with excitation light, but from a practical point of view, it has a wavelength of 400~
300-500nm with excitation light in the 900nm range
It is desirable that the phosphor exhibits stimulated luminescence in the wavelength range of . Examples of the stimulable phosphor used in the radiation image conversion panel of the present invention include those described in U.S. Pat. No. 3,859,527.
SrS: Ce, Sm, SrS: Eu, Sm, ThO ₂ : Er, and La ₂ O ₂ S: Eu, Sm, described in JP-A-55-12142.
ZnS: Cu, Pb, BaO・xAl ₂ O ₃ : Eu (however, 0.8
≦x≦10), and M〓O・xSiO ₂ :A (however,
M〓 is Mg, Ca, Sr, Zn, Cd, or Ba,
A is Ce, Tb, Eu, Tm, Pb, Tl, Bi, or
(Ba _1-xy , Mg _x , Ca _y ) FX: aEu ²⁺ (where X
is at least one of Cl and Br,
x and y are 0<x+y≦0.6 and xy≠0, and a is ^10-6 ≦a≦5× ^10-2 ), as described in JP-A-55-12144.
LnOX:xA (Ln is La, Y, Gd, and
At least one of Lu, X is at least one of Cl and Br, A is at least one of Ce and Tb, and x is 0<x<0.1
(Ba _1-x , M ²⁺ _x ) FX:yA (where M ²⁺ is Mg,
at least one of Ca, Sr, Zn, and Cd; X is Cl, Br; and at least one of
at least one of Nd, Yb, and Er; x is 0≦x≦0.6; y is 0≦y≦0.2);
FX・xA: yLn [However, M〓 is Ba, Ca, Sr,
At least one of Mg, Zn, and Cd, A
are BeO, MgO, CaO, SrO, BaO, ZnO,
Al ₂ O ₃ , Y ₂ O ₃ , La ₂ O ₃ , In ₂ O ₃ , SiO ₂ , TlO ₂ ,
ZrO ₂ , GeO ₂ , SnO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , and
At least one of ThO ₂ , Ln is Eu, Tb,
Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Sm,
and at least one of Gd, X is Cl,
Br, and at least one of
x and y are respectively 5×10 ^-5 ≦x≦0.5 and 0<y≦0.2] A phosphor is described in JP-A-56-116777 (Ba _{1- x} , M〓 _x )F ₂・aBaX ₂ :yEu, zA [However,
M〓 is beryllium, magnesium, calcium,
at least one of strontium, zinc, and cadmium; X is at least one of chlorine, bromine, and iodine; A is at least one of zirconium and scandium;
a, x, y, and z are each 0.5≦a≦1.25,
0≦x≦1, 10 ^-6 ≦y≦2×10 ^-1 , and 0<z
≦10 ^-2 ], described in Japanese Patent Application Laid-Open No. 57-23673, (Ba _1-x , M〓 _x )F ₂・aBaX ₂ :yEu, zB ,
M〓 is beryllium, magnesium, calcium,
at least one of strontium, zinc, and cadmium;
10 ^-6 ≦y≦2×10 ^-1 and 0<z≦2×10 ^-1 ] A phosphor is described in JP-A-57-23675 (Ba _{1 -x} , M〓 _x )F ₂・aBaX ₂ :yEu, zA [However,
M〓 is beryllium, magnesium, calcium,
at least one of strontium, zinc, and cadmium; X is at least one of chlorine, bromine, and iodine; A is at least one of arsenic and silicon; a, x, y, and z are each 0.5 ≦a≦1.25, 0≦x≦1, 10 ^-6
≦y≦2×10 ^-1 , and 0<z≦5×10 ^-1 ], M
OX: xCe [However, M〓 is Pr, Nd, Pm, Sm,
At least one trivalent metal selected from the group consisting of Eu, Tb, Dy, Ho, Er, Tm, Yb, and Bi, X is one or both of Cl and Br, and x is 0<x<0.1] A phosphor is described in JP-A-58-206678.
Ba _1-x M _x/2 L _x/2 FX:yEu ²⁺ [However, M is Li, Na,
Represents at least one alkali metal selected from the group consisting of K, Rb, and Cs; L is Sc,
Y, La, Ce, Pr, Nd, Pm, Sm, Gd, Tb,
represents at least one trivalent metal selected from the group consisting of Dy, Ho, Er, Tm, Yb, Lu, Al, Ga, In, and Tl; X is at least one selected from the group consisting of Cl, Br, and A phosphor representing a type of halogen; x is 10 ^-2 ≦x≦0.5, and y is 0<y≦0.1], as disclosed in Japanese Patent Application No. 57-137374 by the applicant BaFX・xA described in: yEu ²⁺ [However, X is
is at least one halogen selected from the group consisting of Cl, Br, and; A is a composition of a tetrafluoroboric acid compound; and x is
10 ^-6 ≦x≦0.1, y is 0<y≦0.1] BaFX xA: yEu described in Japanese Patent Application No. 158048/1983 filed by the present applicant ²⁺ [However, X is
At least one halogen selected from the group consisting of Cl, Br, and A is a hexafluoro compound group consisting of monovalent or divalent metal salts of hexafluorosilicic acid, hexafluorotitanic acid, and hexafluorozirconic acid and x is 10 ^-6 ≦x≦0.1, and y is 0<y≦0.1]; Patent application filed by the present applicant BaFX・xNaX′: aEu ²⁺ described in specification No. 166320/1982 [However,
X and X' are each at least one of Cl, Br, and x and a are 0<x≦2 and 0<a≦0.2]; M〓FX・xNaX′:yEu ²⁺ :zA [where M〓 is at least one member selected from the group consisting of Ba, Sr, and Ca] as described in the specification of Japanese Patent Application No. 166696/1983 by the applicant. X and X' are each at least one halogen selected from the group consisting of Cl, Br, and; A is selected from V, Cr, Mn, Fe, Co, and Ni and x is 0<x≦2, y is 0<y≦
0.2, and z is 0<z≦10 ^-2 ], M〓FX・aM〓X′ described in the specification of Japanese Patent Application No. 184455/1983 filed by the present applicant.・bM′〓X″ ₂・cM〓
X3・xA:yEu ²⁺ [However, M〓 is at least one kind of alkaline earth metal selected from the group consisting of Ba, Sr, and Ca; M〓 is Li, Na, K,
is at least one kind of alkali metal selected from the group consisting of Rb, and Cs; M′〓 is Be and
is at least one divalent metal selected from the group consisting of Mg; M is at least one trivalent metal selected from the group consisting of Al, Ga, In, and Tl; A is a metal oxide; X is Cl, Br,
and I, and X′, X″, and X are F,
at least one kind of halogen selected from the group consisting of Cl, Br, and I; and a is 0≦
a≦2, b is 0≦b≦10 ^-2 , c is 0≦c≦10 ^-2 ,
and a+b+c≧10 ^-6 ; x is 0<x≦0.5,
y is 0<y≦0.2], and the like.

Among the above-mentioned stimulable phosphors, divalent europium-activated alkaline earth metal fluorohalide phosphors and rare earth element-activated rare earth oxyhalide phosphors exhibit high-brightness stimulated luminescence, so preferable. However, the stimulable phosphor used in the present invention is not limited to the above-mentioned phosphors, and when irradiated with radiation and then irradiated with excitation light,
Any phosphor that exhibits stimulated luminescence 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, and vinylidene chloride. Binders represented by synthetic polymeric substances such as vinyl chloride copolymers, polyalkyl (meth)acrylates, vinyl chloride/vinyl acetate copolymers, polyurethanes, cellulose acetate butyrate, polyvinyl alcohol, linear polyesters, etc. can. Particularly preferred among such binders are nitrocellulose, linear polyesters, polyalkyl(meth)
acrylates, mixtures of nitrocellulose and linear polyesters and mixtures of nitrocellulose and polyalkyl (meth)acrylates.
Note that these binders may be crosslinked with a crosslinking agent.

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

First, the above-mentioned stimulable phosphor and binder are added to a suitable solvent and thoroughly mixed to prepare a coating solution in which phosphor particles are uniformly dispersed in the binder solution.

Examples of solvents for preparing coating solutions include lower alcohols such as methanol, ethanol, n-propanol, and n-butanol; chlorine-containing hydrocarbons such as methylene chloride and ethylene chloride; and ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone. ; esters of lower fatty acids and lower alcohols such as methyl acetate, 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 stimulable phosphor in the coating solution varies depending on the characteristics of the intended radiation image conversion panel, the type of phosphor, etc., but in general, the mixing ratio of the binder and the stimulable phosphor is , 1:1 to 1:100 (weight ratio), and particularly preferably 1:8 to 1:40 (weight ratio).

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

The coating solution containing the phosphor and binder prepared as described above is then uniformly applied to the surface of the support to form a coating film of the coating solution. This coating operation can be carried out using conventional coating means such as a doctor blade, roll coater, knife coater, etc.

The formed coating film is then dried by gradually heating to complete the formation of the phosphor layer on the support. The thickness of the phosphor layer varies depending on the characteristics of the intended radiation image conversion panel, the type of phosphor, the mixing ratio of binder and phosphor, etc., but usually
The thickness should be 20 μm to 1 mm. However, the thickness of this layer is preferably 50 to 500 μm.

Note that the phosphor layer does not necessarily need to be formed by directly applying a coating liquid onto the support as described above; for example, it is possible to form the phosphor layer by separately applying the coating liquid onto a sheet such as a glass plate, metal plate, plastic sheet, etc. After the phosphor layer is formed by drying, it may be pressed onto the support, or the support and the phosphor layer may be bonded together using an adhesive.

Next, a protective film is provided on the phosphor layer via a colored adhesive layer, which is a characteristic feature of the present invention.

Examples of adhesives used in the adhesive layer in the radiation image storage panel of the present invention include polyacrylic resins, polyester resins, polyurethane resins, polyvinyl acetate resins, and ethylene/vinyl acetate copolymers. be able to. The adhesive is not limited to the above-mentioned resins, and for example, any resin conventionally known as an adhesive can be used.

Further, the coloring agent used to color the adhesive is a coloring agent that absorbs at least a portion of the excitation light for causing the stimulable phosphor constituting the phosphor layer of the panel to stimulate luminescence. It is. This colorant has reflective properties such that the average reflectance in the excitation light wavelength region of the stimulable phosphor used in the panel is smaller than the average reflectance in the stimulated emission wavelength region of the stimulable phosphor. It is preferable that

From the viewpoint of improving the line sharpness of the image, it is preferable that the average reflectance of the colorant in the excitation light wavelength range of the stimulable phosphor is as small as possible. On the other hand, from the viewpoint of sensitivity, it is preferable that the average reflectance in the stimulated emission wavelength region of the stimulable phosphor of the colorant is as large as possible.

Therefore, the preferred colorant will vary depending on the type of stimulable phosphor used in the radiation image storage panel. As mentioned above, the phosphors used in the radiation image conversion panel of the present invention include 400~
300~ by excitation light in the wavelength range of 900nm
A phosphor that exhibits stimulated luminescence in a wavelength range of 500 nm is preferable. For such stimulable phosphors, blue to green color should be used so that the average reflectance in the excitation wavelength region is smaller than the average reflectance in the stimulated emission wavelength region and the difference between the two is as large as possible. colorants are used.

Examples of blue to green colorants (dyes and pigments) preferably used in the present invention include colorants such as those disclosed in JP-A-55-163500, i.e., pomelo first blue.
3G (manufactured by Hoechst), Estrol Bryl Blue N-3RL (manufactured by Sumitomo Chemical Co., Ltd.), Sumia Acrylic Blue F
-GSL (manufactured by Sumitomo Chemical Co., Ltd.), D&C Blue No. 1 (manufactured by National Aniline Co., Ltd.), Spirit Blue (manufactured by Hodogaya Chemical Co., Ltd.), Oil Blue No. 603 (manufactured by Orient Co., Ltd.), Kitten Blue A (manufactured by Ciba Gaiki Co., Ltd.), Eisenkatilone Blue GLH (manufactured by Hodogaya Chemical Co., Ltd.), Lake Blue AFH (manufactured by Kyowa Sangyo Co., Ltd.), Rhodalin Blue 6GX (manufactured by Kyowa Sangyo Co., Ltd.), Brimocyanin 6GX (Inabata Sangyo Co., Ltd.), Brill Acid Green 6BH (Hodogaya Chemical Co., Ltd.), Cyanine Blue BNRS (Toyo Ink Co., Ltd.), Lionol Blue SL (Toyo Ink Co., Ltd.)
Organic _colorants such as
Examples include inorganic colorants such as ZnO-CoO-NiO pigments.

Also, color index No. 24411 as disclosed in the above-mentioned Japanese Patent Application Laid-open No. 57-96300,
23160, 74180, 74200, 22800, 23150, 23155,
24401, 14880, 15050, 15706, 15707, 17941,
74220, 13425, 13361, 13420, 11836, 74140,
Organic metal complex colorants such as 74380, 74350, and 74460 may also be mentioned.

Among these blue to green colorants, from the viewpoint of graininess and contrast of the obtained image, the latter, as disclosed in Japanese Patent Application Laid-open No. 57-96300, has a wavelength longer than that of the excitation light. Particularly preferred are organic metal complex colorants that do not emit light.

The colored adhesive layer can be formed on the phosphor layer together with the protective film, for example, by the following method.

First, the above resin and colorant are added to a suitable solvent and mixed thoroughly to prepare a coating solution for forming an adhesive layer. As the solvent for preparing the coating solution, the solvent used in forming the phosphor layer described above can be used.

This coating liquid is uniformly applied to the surface of the transparent thin film for the protective film to form a coating film using a conventional coating means such as a doctor blade, roll coater, knife coater, etc. Then,
By adhering (laminating) the coated transparent thin film onto the phosphor layer with the coating facing downward, the formation of the colored adhesive layer and the protective film on the phosphor layer is completed.

In this way, a colored adhesive layer is formed on the phosphor layer. The thickness of the colored adhesive layer varies depending on the characteristics of the intended radiation image conversion panel, the types of materials used for the phosphor layer and protective film, the types of resin and colorant, etc., but is usually 0.1
The thickness is preferably from 10 μm to 10 μm.

Further, the mixing ratio of the resin and the colorant in the coating liquid is generally selected from the range of 10:1 to 10 ⁶ :1 (weight ratio) when the colorant is a dye. When the colorant is a pigment, it is generally 1:10 to ¹⁰⁵ :1.
(weight ratio).

From the viewpoint of sensitivity, the reflectance of the colored adhesive layer in the stimulated emission wavelength region is preferably as large as possible.
Generally, the average reflectance of the colored adhesive layer in the stimulated emission wavelength region is preferably 20% or more of the average reflectance of an equivalent non-colored adhesive layer in the same wavelength region.

On the other hand, from the viewpoint of sharpness, the smaller the reflectance of the colored adhesive layer in the excitation light wavelength region, the better. Generally, the average reflectance of the colored adhesive layer in the excitation light wavelength range is preferably 95% or less of the average reflectance of an equivalent non-colored adhesive layer in the same wavelength range.

However, in the present invention, reflectance means reflectance measured using an integrating spherical spectrophotometer.

Examples of the material for the transparent protective film formed as described above include transparent thin films separately formed from polyethylene terephthalate, polyethylene, vinylidene chloride, polyamide, and the like. The thickness of the transparent protective film is preferably about 3 to 20 μm.

Next, Examples and Comparative Examples of the present invention will be described.
However, these examples do not limit the invention.

Example 1 Methyl ethyl ketone was added to a mixture of divalent europium-activated barium fluoride bromide phosphor (BaFBr:Eu ²⁺ ) particles and an acrylic resin to prepare a dispersion containing phosphor particles in a dispersed state. . After further adding tricresyl phosphate, n-butanol, and methyl ethyl ketone to this dispersion,
Stir and mix thoroughly using a propeller mixer.
The phosphor particles are uniformly dispersed, the mixing ratio of binder and phosphor is 1:30 (weight ratio), and the viscosity is 25 to 35 PS.
(25°C) coating solution was prepared.

Next, a polyethylene terephthalate sheet (support, thickness: 250 μm) was placed horizontally on a glass plate, and the coating solution was uniformly applied thereon using a doctor blade. After coating, the support on which the coating film has been formed is placed in a dryer, and the temperature inside the dryer is gradually raised from 25°C to 100°C.
The paint film was dried. In this way, a phosphor layer having a layer thickness of about 300 μm was formed on the support.

Separately, a polyester resin (adhesive; Vylon #300, manufactured by Toyobo Co., Ltd.) was dissolved in methyl ethyl ketone, and a dye (copper phthalocyanine) was added to this adhesive solution at a solid content ratio of 0.5% to the adhesive. adjusted. This coating solution was applied to a polyethylene terephthalate transparent film (protective film, thickness: 12 μm) at 2 g/ml by the same procedure as above.
m ² was applied to form a coating consisting of colored adhesive.

Then, a transparent film with a coating made of this colored adhesive is placed with the coating side facing down and adhered to the phosphor layer to form a colored adhesive layer and a transparent protective film. , a radiation image storage panel was produced which was composed of a phosphor layer, a colored adhesive layer and a transparent protective film. (Panel a) Furthermore, the amount of dye used to color the adhesive layer was
By changing the solid content ratio to adhesive in the range of 0.1 to 1.0%, various radiations with different degrees of coloring of the adhesive layer consisting of the support, phosphor layer, colored adhesive layer, and transparent protective film can be applied. An image conversion panel was manufactured. (Panel A) Comparative Example 1 The method of Example 1 was repeated except that 0.1% (solid content ratio to binder) of dye (copper phthalocyanine) was added to the coating solution for forming the phosphor layer. A colored phosphor layer was formed on the support by performing the same treatment.

Next, by performing the same treatment as in Example 1 except that no dye was added to the coating solution for forming the adhesive layer, a structure consisting of a support, a colored phosphor layer, an adhesive layer, and a transparent protective film was formed. A radiation image conversion panel was manufactured using the following methods. (Panel b) Furthermore, the amount of dye used to color the phosphor layer was
The support, colored phosphor layer,
Various radiation image conversion panels with different degrees of coloring of the phosphor layer composed of an adhesive layer and a transparent protective film were manufactured. (Panel B) Each of the radiation image conversion panels (panels a, A and panels b, B) obtained as described above,
Evaluation was made by the image sharpness test and sensitivity test described below.

(1) Image sharpness test
After irradiating the line through the MTF chart, the He
-The fluorescent particles are excited by scanning with Ne laser light (wavelength: 632.8 nm), and the stimulated luminescence emitted from the fluorescent layer is received by a photodetector (photomultiplier tube with spectral sensitivity S-5). This was converted into an electrical signal and reproduced as an image by an image reproducing device to obtain an image of the MTF chart on a display device. The modulation transfer function (MTF) was measured from the obtained images.

(2) Sensitivity test A tube voltage of 80KVp was applied to the radiation image conversion panel.
After irradiation with a line, the sensitivity was measured by excitation with He--Ne laser light (wavelength: 632.8 nm).

The results obtained regarding image sharpness are shown in graphical form in FIG.

Figure 1 shows the following: Curve a: The relationship between spatial frequency and MTF value in panel a (Example 1), and Curve b: The relationship between spatial frequency and MTF value in panel b (Comparative example 1). each represents.

The results obtained regarding image sharpness and sensitivity are also shown in graph form in FIG.

In FIG. 2, the horizontal axis represents the difference (decrease) in relative sensitivity when panel b in Comparative Example 1 is taken as the reference (relative sensitivity: 100, sharpness at spatial frequency 2 cycles/mm: 35%), The vertical axis is the difference in sharpness (increase) when panel b is used as the standard.
It represents. In Figure 2, straight line A represents the relationship between relative sensitivity and sharpness in panel A (Example 1), and straight line B represents the relationship between relative sensitivity and sharpness in panel B (comparative example 1). ing.

As is clear from the results summarized in FIG. 1, the radiation image conversion panel of the present invention (panel a) has significantly improved sharpness compared to the conventional radiation image conversion panel (panel b).

Furthermore, from graph A and graph B shown in FIG.
It is clear that the conventional radiation image conversion panel (panel B, disclosed in JP-A-57-96300) provides images with significantly higher sharpness than the known radiation image conversion panel (panel B, disclosed in Japanese Patent Application Laid-open No. 57-96300) when the sensitivity is the same. .

Example 2 In Example 1, the layer thickness of the phosphor layer was 150 μm.
A radiation image storage panel consisting of a support, a phosphor layer, a colored adhesive layer and a transparent protective film was manufactured by carrying out the same treatment as in Example 1 except for the following.

Furthermore, the amount of dye used to color the adhesive layer
By changing the solid content ratio to adhesive in the range of 0.1 to 1.0%, various radiations with different degrees of coloring of the adhesive layer consisting of the support, phosphor layer, colored adhesive layer, and transparent protective film can be applied. An image conversion panel was manufactured. (Panel C) Comparative Example 2 In Comparative Example 1, the layer thickness of the colored phosphor layer was
A radiation image conversion panel consisting of a support, a colored phosphor layer, an adhesive layer and a transparent protective film was manufactured by carrying out the same treatment as in Comparative Example 1 except that the thickness was 150 μm. (Panel d) Next, each of the obtained radiation image conversion panels (Panels C and d) was evaluated by the above image sharpness test and sensitivity test.

The results obtained are shown in graphical form in FIG.

In FIG. 2, straight line C: represents the relationship between relative sensitivity and sharpness in panel C (Example 2). In this case, panel d (relative sensitivity: 100, spatial frequency 2 cycles/
Sharpness in mm: 55%) is used.

From graph C shown in FIG. 2, it is clear that the radiation image storage panel according to the present invention exhibits a similar tendency even when the thickness of the phosphor layer is made thinner, and is sharper than the conventional radiation image storage panel at the same sensitivity. It is clear that the degree of improvement is improved.

[Brief explanation of the drawing]

FIG. 1 shows a radiation image conversion panel of the present invention (curve a) and a conventional radiation image conversion panel (curve b).
It is a graph showing MTF for. Figure 2 shows
It is a graph showing the relationship between relative sensitivity and sharpness in the radiation image conversion panel of the present invention (straight lines A, C) and the known radiation image conversion panel (straight line B).

Claims (1)

[Scope of Claims] 1. A radiation image storage panel comprising, in this order, a support, a phosphor layer comprising a supporting binder containing a stimulable phosphor in a dispersed state, an adhesive layer, and a protective film, wherein the adhesive 1. A radiation conversion panel characterized in that the layer is colored with a colorant that absorbs at least a portion of excitation light for causing a stimulable phosphor to stimulably emit light. 2. The adhesive layer is colored with a colorant whose average reflectance in the excitation light wavelength region of the stimulable phosphor is smaller than the average reflectance in the stimulated emission wavelength region of the stimulable phosphor. A radiation image conversion panel according to claim 1, characterized in that: 3 The average reflectance of the colored adhesive layer in the excitation light wavelength region is 95% higher than the average reflectance of the equivalent uncolored adhesive layer in the excitation light wavelength region.
% or less, the radiation image conversion panel according to claim 2. 4. The average reflectance of the colored adhesive layer in the stimulated emission wavelength range is 20% or more of the average reflectance of the equivalent non-colored adhesive layer in the stimulated emission wavelength range. A radiation image conversion panel according to claim 2. 5. Claim 1, wherein the stimulable phosphor is a phosphor that exhibits stimulated luminescence in a wavelength range of 300 to 500 nm when stimulated by excitation light in a wavelength range of 400 to 900 nm. The radiation image conversion panel according to any one of items 4 to 4. 6. The radiation image conversion panel according to claim 5, wherein the stimulable phosphor is a divalent europium activated alkaline earth metal fluorohalide phosphor. 7. The radiation image conversion panel according to claim 5, wherein the stimulable phosphor is a rare earth element-activated rare earth oxyhalide phosphor.