JPH0314158B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a radiation image storage panel and a method for manufacturing the same. More specifically, the present invention includes a support, a binder provided on the support, and a stimulable phosphor containing a composition ratio of 1:25 to 1:100 (by weight). The present invention relates to a radiation image conversion panel substantially composed of a resin layer and a method for manufacturing the same. As a method of obtaining a radiation image as an image, a so-called radiography method has conventionally been used in which a radiographic film having an emulsion layer made of a silver salt photosensitive material is combined with an intensifying screen. Recently, radiographic imaging using a stimulable phosphor as described in U.S. Pat. Conversion methods are now attracting attention. This radiation image conversion method uses a radiation image conversion panel (stimulable phosphor sheet) having a stimulable phosphor.
The stimulable phosphor of the panel absorbs the radiation transmitted through the subject or the radiation emitted from the subject, and then the stimulable phosphor is exposed to electromagnetic waves selected from visible light and infrared rays. By exciting the stimulable phosphor in a time-series manner with (excitation light), the radiation energy accumulated in the stimulable phosphor is released as fluorescence (stimulated luminescence), and this fluorescence is read photoelectrically to generate an electrical signal. The electrical signals obtained are then converted into images. 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 basic structure of the radiation image conversion panel used in the above-mentioned radiation image conversion method is a support and a phosphor-containing resin layer provided on one side of the support. Note that the surface of this phosphor-containing resin layer opposite to the support (the surface not facing the support)
Generally, a transparent protective film is provided to protect the phosphor-containing resin layer from chemical alteration or physical impact. The phosphor-containing resin layer is made of a binder that contains and supports stimulable phosphor particles in a dispersed state.
The phosphor-containing resin layer is generally attached to the support using a coating method under normal pressure as described below. That is, a coating solution is prepared by mixing and dispersing stimulable phosphor particles and a binder in a suitable solvent, and this coating solution is coated under normal pressure using a coating means such as a doctor blade, roll coater, or knife coater. The coating solution can be coated directly onto the support of the radiation image storage panel and then the solvent removed from the coating, or the coating solution may be coated in advance on a temporary support such as a glass plate under normal pressure and then coated. By removing the solvent from the film to form a phosphor-containing resin thin film, peeling it off from the temporary support and bonding it to the support of the radiation image conversion panel, the phosphor-containing resin layer is formed as a support. are being added to. The stimulable phosphor particles in the phosphor-containing resin layer are
After absorbing radiation such as radiation, it emits light (stimulated luminescence) when irradiated with electromagnetic waves selected from visible light and infrared rays. Therefore, the radiation transmitted through the object or emitted from the object is absorbed by the phosphor-containing resin layer of the radiation image conversion panel in proportion to the amount of radiation.
A radiation image of a subject or a subject is formed on the radiation image conversion panel as an image of accumulated radiation energy. This accumulated image can be emitted as stimulated luminescence (fluorescence) by exciting it with electromagnetic waves (excitation light) selected from visible light and infrared rays, and this stimulated luminescence can be read photoelectrically and converted into an electrical signal. This makes it possible to image the accumulation of radiation energy. 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 a high sensitivity, similar to the intensifying screen used in conventional radiography. It is desired that the image quality (sharpness, graininess, etc.) is good. Regarding image sharpness, from the point of view of obtaining more accurate and detailed information about the subject or subject, it is desired to develop a radiation image conversion panel that improves the sharpness of the obtained image even slightly. . An object of the present invention is to provide a radiation image conversion panel that provides images with improved sharpness and a method for manufacturing the same. The above purpose is to achieve a composition ratio of the support, the binder provided on the support, and the stimulable phosphor of 1:25.
In a radiation image conversion panel substantially composed of a phosphor-containing resin layer in a range of 1:100 (weight ratio), the porosity of the phosphor-containing resin layer is determined by a normal coating method under normal pressure. This can be achieved by the radiation image storage panel of the present invention, which has a porosity of 90% or less of the porosity of the phosphor-containing resin layer having the composition ratio. Further, the above-mentioned radiation image storage panel has the following characteristics: (1) The composition ratio of the support, the binder formed on the support by a normal coating method under normal pressure, and the stimulable phosphor. By compressing a sheet substantially composed of a phosphor-containing resin layer in a range of 1:25 to 1:100 (weight ratio), the porosity of the phosphor-containing resin layer is reduced to the level before the compression treatment. A method for producing a radiation image storage panel of the present invention, characterized in that the porosity is 90% or less, or (2) a method for producing a radiation image storage panel using a binder and a stimulable phosphor formed by a normal coating method under normal pressure. The composition ratio is 1:25~
By compressing the phosphor-containing resin layer in the range of 1:100 (weight ratio), the porosity of the phosphor-containing resin layer is reduced to 90% or less of the porosity before the compression treatment, and then the phosphor-containing resin layer is compressed. The method for producing a radiation image storage panel of the present invention is characterized in that a resin layer is provided on a support. Next, the present invention will be explained in detail. The present invention improves the porosity of the phosphor-containing resin layer of a radiation image storage panel in which the composition ratio of the binder and the stimulable phosphor is in the range of 1:25 to 1:100 (weight ratio). By reducing the porosity to a certain level or less than the porosity of the phosphor-containing resin layer having the composition ratio formed by the coating method described below, the sharpness of the radiation image conversion panel can be significantly improved, that is, the radiation image conversion panel can be improved. When the electrical signals obtained are converted into images when used, the sharpness of the images is significantly improved. That is, when forming a phosphor-containing resin layer (hereinafter simply referred to as phosphor layer) consisting of a stimulable phosphor and a binder on a support by a normal coating method under normal pressure, the phosphor layer Air tends to be mixed into the phosphor layer, which tends to cause voids in the phosphor layer. These voids are particularly likely to occur around phosphor particles,
Furthermore, as the content of the phosphor in the binder increases, the phosphor particles become denser, and there is a problem that a large number of voids are likely to be formed between the phosphor particles. By the way, in the radiation image conversion method using the above-mentioned stimulable phosphor, when the radiation transmitted through the subject or emitted from the subject enters the phosphor layer of the radiation image conversion panel, the phosphor layer contains and supports the radiation. Each particle of the phosphor absorbs the energy of the radiation, and an image of accumulated radiation energy corresponding to a radiation image of the subject or subject is formed in the phosphor layer. Next, when this radiation image conversion panel is irradiated with electromagnetic waves (excitation light) in the visible to infrared region, the irradiated phosphor particles instantaneously emit light in the near-ultraviolet to visible region. This fluorescence (stimulated luminescence) is directly incident on a photoelectric conversion device such as a photomultiplier tube that moves close to the surface of the panel and is converted into an electrical signal, thereby converting the target radiation energy accumulation image into an image. You get it in form. Generally, it is known that as the amount of phosphor contained in the phosphor layer increases, the amount of light emitted increases, and therefore the sensitivity improves. On the other hand, it is also known that sharpness depends on the thickness of the phosphor layer. In other words, the thicker the phosphor layer becomes, the more pronounced the diffusion of excitation light in the phosphor layer becomes, and as a result, the output (fluorescence) from a wider area than the irradiation target phosphor particle group is recorded. The sharpness of the image formed based on the output signal will be reduced. Therefore, by making the phosphor layer thinner, images with improved sharpness can be obtained. According to studies by the present inventors, the layer is substantially composed of a phosphor-containing resin layer in which the composition ratio of the binder and the stimulable phosphor is in the range of 1:25 to 1:100 (weight ratio). In the radiation image conversion panel, the porosity of the phosphor layer is 90% of the porosity of the phosphor-containing resin layer of the composition ratio formed by a normal coating method under normal pressure.
By setting the following, the density of the phosphor in the phosphor layer is made higher than the density of the phosphor in the conventional radiation image conversion panel, and as a result, the thickness of the phosphor layer is made thinner, thereby reducing the sensitivity. It has been found that the sharpness of an image can be significantly improved without any accompanying effects. Furthermore, since the radiation image conversion panel of the present invention has a phosphor layer with a higher density of stimulable phosphor than the density of the stimulable phosphor in the phosphor layer of a conventional radiation image conversion panel, for example, the radiation image conversion panel of the present invention If the phosphor layer of the image conversion panel has the same layer thickness as the phosphor layer of a conventional radiation image conversion panel, the phosphor layer of the radiation image conversion panel of the present invention contains more stimulable phosphor particles. Therefore, according to the radiation image conversion panel of the present invention, it is possible to improve the sensitivity without reducing the sharpness. That is, when comparing the same sharpness, the radiation image conversion panel of the present invention has higher sensitivity than the conventional radiation image conversion panel. Conversely, when comparing the same sensitivity, the radiation image conversion panel of the present invention has higher sharpness than the conventional radiation image conversion panel. 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. In the radiation image storage panel of the present invention, the phosphor-containing resin layer is basically a layer made of a binder containing and supporting phosphor particles 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, the wavelength is 450 ~
A phosphor that exhibits stimulated luminescence by excitation light in the 800 nm range is desirable. 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.
Phosphors expressed by composition formulas such as SrS: Ce, Sm, SrS: Eu, Sm, ThO ₂ : Er, and La ₂ O ₂ S: Eu, Sm, etc., as 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
A phosphor represented by a composition formula such as (Ba _1-xy , Mgx, Cay) FX: aEu ²⁺ [However,
is at least one of Cl and Br,
A phosphor represented by the composition formula: x and y are 0<x+y≦0.6 and xy≠0, and a is 10 ^-6 ≦a≦5×10 ^-2 JP-A-12144-1987 stated in the issue
LnOX: xA [However, 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
A phosphor represented by the composition formula of (Ba _1-x , M〓
At least one of Ca, Sr, Zn, and Cd, X is at least one of Cl, Br, and I, A is Eu, Tb, Ce, Tm, Dy, Pr, Ho,
At least one of Nd, Yb, and Er, and x is 0≦x≦0.6, and y is 0≦y≦0.2] JP-A-55-160078 M〓 stated in the issue
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 I,
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 [where ,
M〓 is beryllium, magnesium, calcium,
at least one of strontium, zinc, and cadmium;
10 ^-6 ≦y≦2×10 ^-1 and 0<z≦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≦10 ^-1 ], M〓OX described in the specification of Japanese Patent Application No. 167498/1983 filed by the present applicant. :xCe[However, M〓 is Pr,
Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm,
At least one trivalent metal selected from the group consisting of Yb and Bi, X is either one or both of Cl and Br, and x satisfies 0<x<0.1] The phosphor represented by (Ba _1-x , M _X/2 L _X/2 FX: yEu ²⁺ [where M is Li , represents at least one alkali metal selected from the group consisting of Na, K, Rb, and Cs; L is Sc, Y, La, Ce, Pr, Nd,
Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb,
represents at least one trivalent metal selected from the group consisting of Lu, Al, Ga, In, and Tl;
represents at least one halogen selected from the group consisting of Cl, Br, and I; and x is
10 ^-2 ≦x≦0.5, y is 0<y≦0.1] BaFX xA:yEu described in Japanese Patent Application No. 137374/1983 by the present applicant ²⁺ [However, X is
is at least one halogen selected from the group consisting of Cl, Br, and I; A is a fired product 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 I; A is a hexafluoro compound consisting of a monovalent or divalent metal salt of hexafluorosilicic acid, hexafluorotitanic acid, and hexafluorozirconic acid; and x is 10 ^-6 ≦x≦0.1, and y is 0<y≦0.1. BaFX xMaX': aEu ²⁺ described in Application No. 166320/1983 [However,
X and X' are each at least one of Cl, Br, and I, and x and a are 0<x≦2 and 0<a≦0.2, respectively]; ^M〓FX . is a kind of alkaline earth metal; X and X' are Cl, Br, and I, respectively.
at least one halogen selected from the group consisting of; A is at least one transition metal 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〓
X”' ₃・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 alkali metal selected from the group consisting of Rb, and Cs; M'〓 is Be and
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,
is at least one kind of halogen selected from the group consisting of
At least one halogen selected from the group consisting of F, Cl, Br, and I; and a is 0≦a≦2, b is 0≦b≦10 ^-2 , and c is 0≦c≦.
10 ^-2 , and a+b+c≧10 ^-6 ; x is 0<x
≦0.5, y is 0<y≦0.2]. However, the stimulable phosphor used in the present invention is not limited to the above-mentioned phosphors, but any phosphor that exhibits stimulated luminescence when irradiated with radiation and then irradiated with excitation light. It may be. 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, chloride Examples of binders include synthetic polymeric materials such as vinylidene/vinyl chloride copolymer, polymethyl methacrylate, vinyl chloride/vinyl acetate copolymer, polyurethane, cellulose acetate butyrate, polyvinyl alcohol, linear polyester, etc. . Particularly preferred among such binders are nitrocellulose, linear polyesters, and mixtures of nitrocellulose and linear polyesters. The phosphor layer can be formed on the support by, for example, the following coating method. First, the above-mentioned phosphor particles and binder are added to a suitable solvent and mixed thoroughly to prepare a coating solution in which the 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 composition ratio of the binder and the phosphor particles in the coating solution varies depending on the characteristics of the intended radiation image conversion panel, the type of phosphor particles, etc., but is in the range of 1:25 to 1:100 (weight ratio). It is particularly preferable to select from the range of 1:25 to 1:85 (weight ratio). The coating liquid also 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. Various additives, such as plasticizers, may be mixed to make the material more durable. 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 particles 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 particles, the mixing ratio of the binder and the phosphor particles, but is usually 20 μm to 1 mm. However, the thickness of this layer is preferably 50 to 500 μm. Note that the phosphor-containing resin layer does not necessarily need to be formed by directly applying a coating liquid onto the support as described above;
After forming a phosphor layer by applying a coating liquid onto a sheet (temporary support) such as a plastic sheet and drying it, this can be pressed onto the support, or
Alternatively, the support and the phosphor layer may be bonded together using an adhesive or the like. The support used in the present invention can be arbitrarily selected from various materials used as supports for intensifying screens in conventional radiography.
Examples of such materials include cellulose acetate, polyester, polyethylene terephthalate, polyamide, polyimide, triacetate,
Films made of plastic materials such as polycarbonate, metal sheets such as aluminum foil and aluminum alloy foil, regular paper, baryta paper, resin-coated paper, pigment paper containing pigments such as titanium dioxide, and paper sized with polyvinyl alcohol, etc. can be mentioned. However, in consideration of the characteristics and handling of the radiation image storage 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, gelatin is added to the surface of the support on the side where the 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 of the radiation image conversion panel. It is also possible to apply a polymeric substance such as to form an adhesion-imparting layer, or to provide a light-reflecting layer made of a light-reflecting substance such as titanium dioxide, or a light-absorbing layer made of a light-absorbing substance such as carbon black. It is. 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 No. 57-82431 filed by the present applicant, in order to improve the sharpness of the resulting image, the surface of the support on the phosphor layer side (the phosphor layer side of the support) When an adhesion-imparting layer, a light-reflecting layer, a light-absorbing layer, or the like is provided on the surface of the layer, irregularities may be formed on the surface. The porosity of the phosphor-containing resin layer formed on the support as described above can be theoretically determined by the following equation (). Vair/V= (a+b)ρxρyV−A(aρy+bρx) V[(a+b)ρxρy−aρyρair−bρxρair] …() (However, V: Total volume of the phosphor layer Vair: Air volume in the phosphor layer A: Total weight of the phosphor ρx: Density of the phosphor ρy: Density of the binder ρair: Density of air a: Weight of the phosphor b: Weight of the binder) Furthermore, in equation (), since ρair is ~0, ( ) can be approximately expressed by the following (). Vair/V= (a+b)ρxρyV−A(aρy+bρx) V[(a+b)ρxρy]... () (However, the definitions of V, Vair, A, ρx, ρy, a, and b are the same as in equation (). In the present invention, the porosity of the phosphor-containing resin layer was calculated using the formula (). As an example, the formation of a phosphor-containing resin layer on a support, consisting of a divalent europium-activated barium fluoride bromide phosphor and a mixture of linear polyester and nitrocellulose as a binder, can be carried out as described above. The coating method is carried out under normal pressure, and specifically, for example, as follows. A mixture of linear polyester and nitrocellulose and particles of divalent europium-activated barium fluoride bromide phosphor (BaFBr:Eu ²⁺ ) were mixed in a composition ratio of 1:1.
40 (weight ratio) in methyl ethyl ketone using a propeller mixer to prepare a coating solution with a viscosity of 30PS (at 25°C). After uniformly applying this coating solution onto polyethylene terephthalate (support) using a doctor blade, the coating is placed in a dryer and the temperature inside the container is gradually raised from 25℃ to 100℃ to dry the coating film. By doing so, a phosphor-containing resin layer is formed on the support. The porosity of the phosphor-containing resin layer formed in this way with a composition ratio of binder and phosphor of 1:40 is
It was 29.4%. In addition, the porosity of a phosphor-containing resin layer with a composition ratio of binder and phosphor of 1:80, which was formed in the same manner as above except for changing the amounts of binder and phosphor used, was 32.6%. It was hot. The above phosphor-containing resin layer is a typical example of a phosphor layer formed by a normal coating method under normal pressure, and can be obtained even if the binder, phosphor particles, and solvent used are changed. The porosity of the phosphor layer does not change significantly. Furthermore, in the calculation of the porosity in equation (), the additive added to the coating liquid is in a small amount and can be ignored. Furthermore, the porosity of the phosphor layer is not significantly affected by changes in coating conditions as long as it is within the range of commonly practiced coating operations. Therefore, as is clear from the above equation (), the biggest factor that changes the porosity of the phosphor-containing resin layer is the composition ratio of the binder and the phosphor [b:a in the definition of the equation (), weight ratio]. As the ratio of the phosphor particles to the binder increases in the phosphor-containing resin layer, the average distance between the phosphor particles dispersed in the binder becomes shorter and voids are more likely to be formed therebetween. Therefore, the porosity of the phosphor-containing resin layer tends to increase as the amount of phosphor increases. In the method for manufacturing a radiation image conversion panel of the present invention, next, a portion of air mixed in the phosphor layer is removed to reduce voids. This reduction in voids is achieved, for example, by compressing the phosphor layer. The compression treatment of the phosphor layer is generally 50 to 1500Kg/cm ²
The heating is carried out at a pressure in the range of , and at a temperature in the range from room temperature to around the melting point of the phosphor layer. The compression time is preferably in the range of 30 seconds to 5 minutes. Moreover, the preferable pressure is 300 to 700 Kg/cm ² , and the preferable temperature is 50 to 120° C., although it varies depending on the binder used and the like. Examples of compression devices used for the compression treatment of the present invention include commonly known devices such as calender rolls and hot presses. For example, compression treatment using calender rolls is carried out by passing a sheet consisting of a support and a phosphor layer at a constant speed between rollers heated to a constant temperature. Further, the compression treatment using a hot press is performed by fixing the sheet between two metal plates heated to a certain temperature, and then applying a certain pressure from both sides for a certain period of time. However, the compression device used in the present invention is not limited to these devices, and any device may be used as long as it can compress the sheet as described above while heating it. Note that, for example, when compressing a phosphor-containing resin thin film formed on a temporary support, it is also possible to perform the compression treatment before attaching the thin film to the support of the radiation image conversion panel. In that case, the phosphor-containing resin thin film alone or a composite sheet of the phosphor-containing resin thin film and a temporary support is compressed, and then the compressed phosphor-containing resin thin film is converted into a radiation image. Mounted on the support of the panel. In addition, in a normal radiation image conversion panel,
A transparent protective film for physically and chemically protecting the phosphor layer is provided on the surface of the phosphor layer opposite to the side in contact with the support. Such a transparent protective film is preferably provided also in the radiation image conversion panel of the present invention. The transparent protective film may be made of a transparent material such as a cellulose derivative such as cellulose acetate or nitrocellulose; or a synthetic polymer material such as polymethyl methacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyvinyl acetate, or vinyl chloride/vinyl acetate copolymer. It can be formed by coating the surface of the phosphor layer with a solution prepared by dissolving a polymeric substance in an appropriate solvent. Alternatively, it can also be formed by a method such as adhering a transparent thin film separately formed from polyethylene terephthalate, polyethylene, vinylidene chloride, polyamide, etc. to the surface of the phosphor layer using a suitable adhesive. The thickness of the transparent protective film thus formed is preferably about 3 to 20 μm. The phosphor-containing resin layer of the radiation image conversion panel of the present invention manufactured by the method typified by the method described above (the composition ratio of the binder and the phosphor is in the range of 1:25 to 1:100) The porosity of (a) is 90% or less of the porosity of the phosphor-containing resin layer having the composition ratio formed by a normal coating method under normal pressure. As mentioned above, by reducing the porosity of the phosphor-containing resin layer in the radiation image storage panel, the density of the phosphor in the phosphor layer increases, and therefore, if the amount of phosphor used is constant, the phosphor layer becomes thinner. Therefore, the sharpness of the obtained image is significantly improved without a decrease in sensitivity. Next, Examples and Comparative Examples of the present invention will be described.
However, these examples do not limit the invention. Example 1 A mixture (binder) of a linear polyester resin and nitrocellulose with a degree of nitrification of 11.5% and particles of photostimulable divalent europium-activated barium fluoride bromide phosphor (BaFBr: Eu ²⁺ ) were prepared. Mix at a weight composition ratio of 1:40, add methyl ethyl ketone, and thoroughly stir and mix using a propeller mixer to ensure that the phosphor particles are uniformly dispersed and the viscosity is 30PS (25℃).
A coating solution was prepared. Next, a polyethylene terephthalate sheet (support material, thickness: 250 μm) in which titanium dioxide was kneaded was placed horizontally on a glass plate.
The coating solution was uniformly applied onto this support 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 sheet consisting of a support and a fluorescent layer with a layer thickness of about 300 μm provided on the support was obtained. Next, a sheet consisting of a support and a phosphor layer formed on one side of the support was compressed using a calendar roll at a pressure of 620 Kg/cm ² and a temperature of 100°C. A transparent polyethylene terephthalate film (thickness:
A transparent protective film is formed by placing and adhering a 12μm polyester adhesive (with the adhesive layer side facing down), which consists of a support, a phosphor layer, and a transparent protective film. A radiation image conversion panel was manufactured using the following methods. Example 2 The same sheet consisting of the support produced in Example 1 and the phosphor layer provided on this support was compressed at a pressure of 420 Kg/cm ² and a temperature of 100° C. produced a radiation image conversion panel composed of a support, a phosphor layer, and a transparent protective film by carrying out the same treatment as in Example 1. Example 3 The same sheet consisting of the support produced in Example 1 and the phosphor layer provided on this support was compressed at a pressure of 620 Kg/cm ² and a temperature of 80° C. produced a radiation image conversion panel composed of a support, a phosphor layer, and a transparent protective film by carrying out the same treatment as in Example 1. Example 4 The same sheet consisting of the support produced in Example 1 and the phosphor layer provided on this support was compressed at a pressure of 420 Kg/cm ² and a temperature of 80° C. produced a radiation image storage panel composed of a support, a phosphor layer, and a transparent protective film by carrying out the same treatment as in Example 1. Comparative Example 1 The same process as in Example 1 was carried out, except that the same sheet as the sheet consisting of the support produced in Example 1 and the phosphor layer provided on this support was not compressed. In this way, a radiation image storage panel consisting of a support, a phosphor layer, and a transparent protective film was manufactured. Measured values of the volume and weight of the phosphor layer of each radiation image conversion panel manufactured as described above,
The porosity of the phosphor-containing resin layer was calculated from the density of the phosphor used (5.1 g/cm ³ ) and the density of the binder (1.258 g/cm ³ ) using the formula (). Table 1 shows the results obtained for each phosphor-containing resin layer.

[Table] In addition, each of the radiation image conversion panels manufactured as described above was evaluated by the image sharpness test described below. That is, after irradiating the radiation image conversion panel with X-rays with a tube voltage of 80KVp,
The phosphor is excited by scanning with Ne laser light (632.8 nm), the stimulated luminescence emitted from the phosphor layer is received and converted into an electrical signal, and this is reproduced as an image by an image reproducing device. An image was obtained on a display device. The modulation transfer function (MTF) of the obtained image was measured. The results obtained are summarized and shown in graph form in FIG. Figure 1 shows the relationship between A: spatial frequency and sharpness (MTF value) in the radiation image conversion panel of Example 1, and B: relationship between spatial frequency and sharpness (MTF value) in the radiation image conversion panel of Comparative Example 1. Each represents the relationship between Table 2 shows the results obtained for each radiation image conversion panel (MTF value at a spatial frequency of 2 cycles/mm).

[Table] Example 5 Mixture (binder) of linear polyester resin and nitrocellulose with a degree of nitrification of 11.5% and photostimulable divalent europium-activated barium fluoride bromide phosphor (BaFBr: Eu ²⁺ ) A radiation image conversion panel composed of a support, a phosphor layer, and a transparent protective film was prepared by performing the same treatment as in Example 1 except that the particles were mixed at a weight composition ratio of 1:80. was manufactured. Example 6 The same sheet consisting of the support produced in Example 5 and the phosphor layer provided on this support was compressed at a pressure of 420 Kg/cm ² and a temperature of 100° C. produced a radiation image conversion panel composed of a support, a phosphor layer, and a transparent protective film by carrying out the same treatment as in Example 5. Example 7 The same sheet consisting of the support produced in Example 5 and the phosphor layer provided on this support was compressed at a pressure of 620 Kg/cm ² and a temperature of 80° C. produced a radiation image storage panel composed of a support, a phosphor layer and a transparent protective film by carrying out the same treatment as in Example 5. Example 8 The same sheet consisting of the support produced in Example 5 and the phosphor layer provided on this support was compressed at a pressure of 420 Kg/cm ² and a temperature of 80° C. produced a radiation image conversion panel composed of a support, a phosphor layer, and a transparent protective film by carrying out the same treatment as in Example 5. Comparative Example 2 The same process as in Example 5 is carried out, except that the same sheet consisting of the support produced in Example 5 and the phosphor layer provided on this support is not compressed. In this way, a radiation image storage panel consisting of a support, a phosphor layer, and a transparent protective film was manufactured. The porosity of the phosphor-containing resin layer of each of the radiation image conversion panels manufactured as described above was calculated and determined using the same method as described above. Table 3 shows the results obtained for each phosphor-containing resin layer.

[Table] In addition, each of the radiation image storage panels manufactured as described above was evaluated by the image sharpness test described above. For each radiation image conversion panel, the results obtained (at a spatial frequency of 2 cycles/mm
MTF values) are shown in Table 4.

【table】 [Brief explanation of the drawing]

FIG. 1 is a graph of the modulation transfer function (MTF) of images obtained using the radiation image conversion panels manufactured in Example 1 and Comparative Example 1. In FIG. 1, A represents the relationship between spatial frequency and sharpness (MTF value) in the radiation image conversion panel of Example 1 (the radiation image conversion panel of the present invention), and B
is the relationship between spatial frequency and sharpness (MTF value) in the radiation image conversion panel of Comparative Example 1 (radiation image conversion panel manufactured by a normal coating method),
each represents.

Claims (1)

[Claims] 1. A phosphor-containing resin in which the composition ratio of a support, a binder provided on the support, and a stimulable phosphor is in the range of 1:25 to 1:100 (weight ratio). In a radiation image conversion panel substantially composed of a layer, the porosity of the phosphor-containing resin layer is equal to the porosity of the phosphor-containing resin layer having the composition ratio formed by a normal coating method under normal pressure. A radiographic image conversion panel characterized in that it has a rate of 90% or less. 2. The radiation image storage panel according to claim 1, wherein the stimulable phosphor is a divalent europium-activated alkaline earth metal fluorohalide phosphor. 3. The radiation image according to claim 2, wherein the divalent europium-activated alkaline earth metal fluoride halide phosphor is a divalent europium-activated barium fluoride bromide phosphor. Conversion panel. 4. The radiation image storage panel according to any one of claims 1 to 3, wherein the binder is a mixture of linear polyester and nitrocellulose. 5. Any one of claims 1 to 4, characterized in that the porosity of the phosphor-containing resin layer is reduced by subjecting the phosphor-containing resin layer to compression treatment. The radiation image conversion panel described in the above section. 6. A support, and a composition of a binder and a stimulable phosphor formed by a normal coating method under normal pressure provided on the support in a composition ratio of 1:25 to 1:100 (weight ratio). By compressing a sheet consisting essentially of a phosphor-containing resin layer of
A method for manufacturing a radiation image conversion panel, characterized in that the porosity of the phosphor-containing resin layer is 90% or less of the porosity before compression treatment. 7. Production of a radiation image storage panel according to claim 6, wherein the compression treatment is performed at a pressure of 50 to 1500 Kg/cm ² and at a temperature above room temperature and below the melting point of the binder. Law. 8. The method for manufacturing a radiation image conversion panel according to claim 6, wherein the compression treatment is performed at a pressure of 300 to 700 kg/cm ² and a temperature of 50 to 120°C. 9. The method for manufacturing a radiation image conversion panel according to any one of claims 6 to 8, wherein the compression treatment is performed using a calendar roll. 10. The method for manufacturing a radiation image conversion panel according to any one of claims 6 to 8, wherein the compression process is performed using a hot press. 11. The stimulable phosphor according to any one of claims 6 to 10, wherein the stimulable phosphor is a divalent europium-activated alkaline earth metal fluorohalide phosphor. A method for manufacturing a radiation image conversion panel. 12. The method for producing a radiation image storage panel according to any one of claims 6 to 11, wherein the binder is a mixture of linear polyester and nitrocellulose. 13 The composition ratio of the binder and the stimulable phosphor formed by a normal coating method under normal pressure is 1:25 ~
By compressing the phosphor-containing resin layer in the range of 1:100 (weight ratio), the porosity of the phosphor-containing resin layer is reduced to 90% or less of the porosity before the compression treatment, and then the phosphor-containing resin layer is compressed. A method for producing a radiation image storage panel, which comprises attaching a resin layer to a support. 14 The above compression treatment is carried out at a pressure of 50 to 1500 Kg/cm ² ,
Claim 1, characterized in that the process is carried out at a temperature above room temperature and below the melting point of the binder.
3. A method for producing a radiation image conversion panel according to item 3. 15 The above compression treatment is carried out at a pressure of 300 to 700 Kg/cm ² ,
The method for manufacturing a radiation image conversion panel according to claim 13, wherein the manufacturing method is carried out at a temperature of 50 to 120°C. 16 Claim 13, characterized in that the compression process is performed using a calender roll.
A method for producing a radiation image conversion panel according to any one of Items 1 to 15. 17. The method for manufacturing a radiation image conversion panel according to any one of claims 13 to 15, characterized in that the compression process is performed using a hot press. 18. The stimulable phosphor according to any one of claims 13 to 17, wherein the stimulable phosphor is a divalent europium-activated alkaline earth metal fluorohalide phosphor. A method for manufacturing a radiation image conversion panel. 19. The method for producing a radiation image storage panel according to any one of claims 13 to 18, wherein the binder is a mixture of linear polyester and nitrocellulose.