JPH0664198B2 - Radiation image conversion panel - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a radiation image conversion panel. More specifically, the present invention provides a support, and the composition ratio of the binder and the stimulable phosphor provided on the support is 1: 1 to 1:25 (weight ratio, but 1:25 is included. The present invention relates to a radiation image conversion panel substantially composed of a phosphor-containing resin layer in the range of (1).

[0002]

2. Description of the Related Art As a method for obtaining a radiation image as an image,
Conventionally, a so-called radiographic method has been used in which a radiographic film having an emulsion layer made of a silver salt light-sensitive material and an intensifying screen are combined. Recently, as one of the methods for replacing the radiographic method, for example, a radiographic image using a stimulable phosphor as described in US Pat. No. 3,859,527 and JP-A-55-12145. The conversion method has come to the fore. This radiation image conversion method uses a radiation image conversion panel (stimulable phosphor sheet) having a stimulable phosphor, and the radiation transmitted through the subject or the radiation emitted from the subject is irradiated onto the panel. Accumulated in the stimulable phosphor by absorbing it in the stimulable phosphor and then exciting the stimulable phosphor in time series with an electromagnetic wave (excitation light) selected from visible light and infrared rays. The emitted radiation energy is emitted as fluorescence (stimulated luminescence), the fluorescence is photoelectrically read to obtain an electric signal, and the obtained electric signal is imaged.

The above-mentioned radiation image conversion method has an advantage that a radiation image having a large amount of information can be obtained with a much smaller exposure dose as compared with the conventional radiographic method. Therefore, this radiographic image conversion method is extremely useful in direct medical radiography such as X-ray radiography for the purpose of medical diagnosis.

The radiation image conversion panel used in the above radiation image conversion method has, as a basic structure, a support and a phosphor-containing resin layer provided on one surface thereof. In addition, in general, a transparent protective film is provided on the surface of the phosphor-containing resin layer opposite to the support (the surface not facing the support), and the phosphor-containing resin layer is chemically protected. Protects against physical alteration or physical shock.

The phosphor-containing resin layer comprises a binder which contains and supports stimulable phosphor particles in a dispersed state. The attachment of the phosphor-containing resin layer on the support is generally carried out by utilizing a coating method under normal pressure as described below. That is, the stimulable phosphor particles and the binder are mixed and dispersed in a suitable solvent to prepare a coating solution, and the coating solution is applied under normal pressure using a coating means such as a doctor blade, a roll coater, or a knife coater. After applying directly on the support of the radiation image conversion panel, by removing the solvent from the coating film, or by applying the coating solution in advance on a temporary support such as a glass plate under normal pressure, then from the coating film By removing the solvent to form a phosphor-containing resin thin film, peeling it from the temporary support and bonding it to the support of the radiation image conversion panel, the phosphor-containing resin layer can be attached to the support. Has been done.

The photostimulable phosphor particles in the phosphor-containing resin layer have the property of emitting light (stimulative emission) when they are irradiated with electromagnetic waves selected from visible light and infrared light after absorbing radiation such as X-rays. Is to have. Therefore, the radiation transmitted through the subject or emitted from the subject is absorbed by the phosphor-containing resin layer of the radiation image conversion panel in proportion to the radiation dose, and the radiation of the subject or the subject is displayed on the radiation image conversion panel. The radiation image is formed as an accumulated image of radiation energy. This accumulated image can be emitted as stimulated emission (fluorescence) by exciting with an electromagnetic wave (excitation light) selected from visible rays and infrared rays, and this stimulated emission is photoelectrically read and converted into an electric signal. As a result, it becomes possible to form an accumulated image of radiation energy.

The above-mentioned radiographic image conversion method is a very advantageous image forming method as described above, and the radiographic image conversion panel used in this method is similar to the intensifying screen used in the conventional radiographic method. It is desired to have high sensitivity and to provide an image with good image quality (sharpness, graininess, etc.). Among them, regarding the sharpness of the image, from the viewpoint of obtaining more accurate and detailed information of the subject or the subject, it is desired to develop a radiation image conversion panel in which the sharpness of the obtained image is improved even slightly. .

It is an object of the present invention to provide a radiation image conversion panel which gives an image with particularly improved sharpness.

The above-mentioned object is that the composition ratio of the support, the binder provided on the support and the stimulable phosphor is 1: 1 to 1: 2.
In a radiation image conversion panel substantially composed of a phosphor-containing resin layer in the range of 5 (weight ratio, but not including 1:25), the porosity of the phosphor-containing resin layer is usually It can be achieved by the radiation image conversion panel of the present invention, which has a porosity of 85% or less of the phosphor-containing resin layer having the composition ratio formed by the coating method under pressure.

The above radiation image conversion panel comprises (1) a support, a composition ratio of a binder formed on the support by a usual coating method under normal pressure and a stimulable phosphor. By a compression treatment of a sheet substantially composed of a phosphor-containing resin layer in the range of 1: 1 to 1:25 (weight ratio, but not including 1:25). The layer is formed by the method for producing the radiation image conversion panel of the present invention, which is characterized in that the porosity of the layer is 85% or less of the porosity before the compression treatment, or (2) a normal coating method under normal pressure. The phosphor-containing resin layer having a composition ratio of the binder to the stimulable phosphor in the range of 1: 1 to 1:25 (weight ratio, but not including 1:25) is compressed to obtain the phosphor. After setting the porosity of the containing resin layer to 85% or less of the porosity before the compression treatment, attach the phosphor containing resin layer on the support. The method of manufacturing a radiation image storage panel according to the present invention, which is characterized in that it is provided.

Next, the present invention will be described in detail. The present invention has a composition ratio of the binder and the stimulable phosphor of 1: 1 to 1: 2.
The porosity of the phosphor-containing resin layer of the radiation image conversion panel in the range of 5 (weight ratio, but not including 1:25) is set to the phosphor of the composition ratio formed by a normal coating method under normal pressure. By reducing the porosity of the resin layer to below a certain level, the sharpness of the radiation image conversion panel is significantly improved, that is, the electric signal obtained is imaged when the radiation image conversion panel is used. In this case, the sharpness of the image is significantly improved.

That is, when a phosphor-containing resin layer (hereinafter simply referred to as a phosphor layer) composed of a stimulable phosphor and a binder is formed on a support by a usual coating method under normal pressure. However, air is easily mixed in the phosphor layer, which tends to cause voids in the phosphor layer. This void is particularly likely to occur around the phosphor particles, and further, the phosphor particles become denser as the content of the phosphor with respect to the binder increases,
There is a problem that a large amount of voids are easily generated between the phosphor particles.

In the radiation image conversion method using the stimulable phosphor described above, when the radiation transmitted through the subject or emitted from the subject enters the phosphor layer of the radiation image conversion panel, it is contained in the phosphor layer. Each particle of the stimulable phosphor absorbs the energy of the radiation, and an accumulated image of radiation energy corresponding to the radiation image of the subject or the subject is formed on the phosphor layer. Next, when the radiation image conversion panel is irradiated with electromagnetic waves (excitation light) in the visible to infrared region, the phosphor particles that have been irradiated instantly emit light in the near ultraviolet to visible region. This fluorescence (stimulated emission)
Is directly incident on a photoelectric conversion device such as a photomultiplier tube that moves close to the surface of the panel and converted into an electric signal to obtain a target radiation energy accumulated image in the form of an image or the like. It is generally known that an increase in the amount of the phosphor contained in the phosphor layer leads to an increase in the amount of emitted light and thus an improvement in sensitivity. On the other hand, it is also known that the sharpness depends on the thickness of the phosphor layer. That is, the thicker the phosphor layer, the more prominent the diffusion of the excitation light in the phosphor layer, and the output (fluorescence) from a wider area than the phosphor particle group targeted for irradiation is recorded. The sharpness of the image formed based on the signal will be reduced. Therefore, if the phosphor layer is thinned, an image with improved sharpness can be obtained.

According to the study by the present inventor, the composition ratio of the binder to the stimulable phosphor is 1: 1 to 1:25 (weight ratio, but 1:25.
In a radiation image conversion panel substantially composed of a phosphor-containing resin layer in the range of (4) is not included), the porosity of the phosphor layer is set to the composition ratio formed by a coating method under normal atmospheric pressure. By making the porosity of the phosphor-containing resin layer of 85% or less, 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,
As a result, it has been found that the sharpness of the image can be remarkably improved by reducing the thickness of the phosphor layer without reducing the sensitivity.

Further, since the radiation image conversion panel of the present invention has a phosphor layer having a density higher than that of the stimulable phosphor in the phosphor layer of the conventional radiation image conversion panel, for example, When the phosphor layer of the radiation image storage panel of the present invention has the same layer thickness as the phosphor layer of the conventional radiation image storage panel, the phosphor layer of the radiation image storage panel of the present invention contains more stimulable fluorescent light. Therefore, the radiation image storage panel of the present invention can improve the sensitivity without lowering the sharpness. That is, in comparison of the same sharpness, the radiation image conversion panel of the present invention has higher sensitivity than the conventional radiation image conversion panel. On the contrary, in comparison of 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 above-mentioned preferable characteristics can be manufactured, for example, by the following method.

In the radiation image storage panel of the present invention, the phosphor-containing resin layer is basically a layer composed of a binder which contains and supports stimulable phosphor particles in a dispersed state. The stimulable phosphor is a phosphor that exhibits stimulated emission when irradiated with excitation light after being irradiated with radiation as described above, but from a practical standpoint, the wavelength is in the range of 450 to 800 nm. A phosphor that exhibits stimulated emission upon excitation light is desirable.

Examples of stimulable phosphors used in the radiation image storage panel of the present invention include SrS: Ce, Sm, SrS: Eu, Sm, ThO ₂ : Er, and ThO ₂ : Er described in US Pat. No. 3,859,527. La
A phosphor represented by a composition formula such as ₂ O ₂ S: Eu, Sm,

ZnS: Cu, Pb described in JP-A-55-12142
BaO · xAl ₂ O ₃ : Eu [however, 0.8 ≦ x ≦ 10], and M
^II O · xSiO ₂ : A [where M ^II is Mg, Ca, Sr, Zn, Cd or Ba, and A is Ce, Tb, Eu, Tm, Pb, Tl, Bi, or
Mn, and x is 0.5 ≦ x ≦ 2.5], or the like.

[B] described in JP-A-55-12143
a _lxy , Mg _x , Ca _y ) FX: aEu ²⁺ [where X is Cl and Br
At least one of x and y is 0 <x
+ Y ≦ 0.6 and xy ≠ 0, and a is 10 ⁻⁶ ≦ a ≦ 5 × 1
Phosphor represented by a composition formula of 0 ^-2],

LnOX: xA described in JP-A-55-12144
[Where Ln is at least one of La, Y, Gd, and Lu, X is at least one of Cl and Br, and A is Ce.
And at least one of Tb and x is 0 <
x <0.1], the phosphor represented by the composition formula:

[Ba _1-x , M ^II described in JP-A-55-12145]
_x ) FX: yA [where M ^II is at least one of Mg, Ca, Sr, Zn, and Cd, X is at least one of Cl, Br, and I, and A is Eu, Tb, Ce. , Tm, Dy, Pr, Ho, N
at least one of d, Yb, and Er, and x
Is 0 ≦ x ≦ 0.6, and y is 0 ≦ y ≦ 0.2],

M ^II FX disclosed in Japanese Patent Laid-Open No. 55-160078
xA: yLn [where M ^II is Ba, Ca, sr, Mg, Zn, and Cd
At least one of them, A is BeO, MgO, CaO, SrO, Ba
O, ZnO, Al ₂ O ₃ , Y ₂ O ₃ , La ₂ O ₃ , In ₂ O ₃ , Si
O 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, C
at least one of e, Tm, Dy, Pr, Ho, Nd, Yb, Er, Sm, and Gd, X is at least one of Cl, Br, and I, and x and y are each 5 × 10 5. ^-5 ≤ x
≦ 0.5, and 0 <y ≦ 0.2], the phosphor represented by the composition formula:

(Ba _1-x , described in JP-A-56-116777)
M ^II _x ) F ₂ · aBaX ₂ : yEu, zA [M ^II is at least one of beryllium, magnesium, calcium, strontium, zinc, and cadmium, X is at least one of chlorine, bromine, and iodine, A is at least one of zirconium and scandium, and a, x, y, and z are each 0.5 ≦ a ≦ 1.2.
5, 0 ≦ x ≦ 1, 10 ⁻⁶ ≦ y ≦ 2 × 10 ⁻¹ , and 0 <z ≦ 1
Phosphor represented by a composition formula of 0 ^-2],

(Ba _1-x , M ^II described in JP-A-57-23673)
_x ) F ₂ · aBaX ₂ : yEu, zB [where M ^II is beryllium,
At least one of magnesium, calcium, strontium, zinc and cadmium, X is at least one of chlorine, bromine and iodine, and a, x, y
And z are 0.5 ≦ a ≦ 1.25, 0 ≦ x ≦ 1, 10 ^{−6, respectively.}
≦ y ≦ 2 × 10 ⁻¹ and 0 <z ≦ 2 × 10 ⁻¹ ], the phosphor represented by the composition formula,

[Ba _1-x , M ^II described in JP-A-57-23675]
_x ) F ₂ · aBaX ₂ : yEu, zA [where M ^II is beryllium,
At least one of magnesium, calcium, strontium, zinc and cadmium, X is at least one of chlorine, bromine and iodine, A is at least one of arsenic and silicon, and a, x, y and z are 0.5 ≤ a ≤ 1.25, 0 ≤ x ≤ 1, 10 ^-6 ≤ y
≦ 2 × 10 ⁻¹ , and 0 <z ≦ 5 × 10 ⁻¹ ]

M ^III OX described in Japanese Patent Application No. 56-167498:
xCe [where M ^III is Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho,
At least one trivalent metal selected from the group consisting of Er, Tm, Yb, and Bi, X is one or both of Cl and Br, and x is 0 <x <0.1] A phosphor represented by the composition formula of

Ba _1-x M described in Japanese Patent Application No. 57-89875
_{x / 2} L _{x / 2} FX: yEu ²⁺ [where M is Li, Na, K, Rb and
Represents at least one alkali metal selected from the group consisting of Cs; L is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, G
d, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga, In, and T
represents at least one trivalent metal selected from the group consisting of l; X represents at least one halogen selected from the group consisting of Cl, Br and I; and x represents 10 ^-2 ≤
x ≦ 0.5, y is 0 <y ≦ 0.1], the phosphor represented by the composition formula:

BaFX described in Japanese Patent Application No. 57-137374
xA: yEu ²⁺ [wherein X is at least one halogen selected from the group consisting of Cl, Br, and I; A is a calcined product of a tetrafluoroborate compound; and x
Is 10 ⁻⁶ ≦ x ≦ 0.1, and y is 0 <y ≦ 0.1],

BaFX described in Japanese Patent Application No. 57-158048
xA: yEu ²⁺ [wherein X is at least one halogen selected from the group consisting of Cl, Br, and I; A is one of hexafluorosilicic acid, hexafluorotitanic acid, and hexafluorozirconic acid; A calcined product of at least one compound selected from the group of hexafluoro compounds consisting of salts of divalent or divalent metals; and x is 10 ⁻⁶
≦ x ≦ 0.1 and y is 0 <y ≦ 0.1], the phosphor represented by the composition formula:

BaFX.xN described in Japanese Patent Application No. 57-166320
aX ′: aEu ²⁺ [where X and X ′ are Cl and B, respectively]
r and at least one of I, x and a
Are 0 <x ≦ 2 and 0 <a ≦ 0.2, respectively,],

M ^II FX described in Japanese Patent Application No. 57-166696
XNaX ′: yEu ²⁺ : zA [where M ^II is Ba, Sr and Ca
Is at least one alkaline earth metal selected from the group consisting of; X and X'are at least one halogen selected from the group consisting of Cl, Br and I; A is V, Cr, Mn, At least one transition metal selected from Fe, Co, and Ni; and x is 0 <x ≦
2, y is 0 <y ≦ 0.2, and z is 0 <z ≦ 10 ⁻² ],

M ^II FX described in Japanese Patent Application No. 57-184455
^{· AM I X '· bM'} II X "2 · cM III X 3 · xA: yEu 2+ [ However, M ^II is Ba, Sr, and is at least one alkaline earth metal selected from the group consisting of Ca ; M ^I is Li, N
a, K, Rb, and is at least one alkali metal selected from the group consisting of Cs; M ^'II is at least one trivalent metal selected from the group consisting of Be and Mg; M
^III is at least one trivalent metal selected from the group consisting of Al, Ga, In, and Tl; A is a metal oxide; X
Is at least one halogen selected from the group consisting of Cl, Br and I; X ′, X ″ and X are F, Cl,
At least one halogen selected from the group consisting of 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 so on.

However, the stimulable phosphor used in the present invention is not limited to the above-mentioned phosphor, and may be a phosphor that exhibits stimulated emission when irradiated with excitation light after irradiation with radiation. It can be anything.

Examples of the binder for the phosphor layer are proteins such as gelatin, polysaccharides such as dextran, or natural polymer substances such as gum arabic; and polyvinyl butyral, polyvinyl acetate, nitrocellulose, ethyl cellulose, Examples include binders represented by synthetic polymer substances such as vinylidene chloride / vinyl chloride copolymer, polymethylmethacrylate, vinyl chloride / vinyl acetate copolymer, polyurethane, cellulose acetate butyrate, polyvinyl alcohol, and linear polyester. it can. 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 phosphor particles and the binder are added to an appropriate solvent and mixed sufficiently to prepare a coating solution in which the phosphor particles are uniformly dispersed in the binder solution.

Examples of the solvent for preparing the coating solution include lower alcohols such as methanol, ethanol, n-propanol and n-butanol; hydrocarbons containing chlorine atom such as methylene chloride and ethylene chloride; acetone, methyl ethyl ketone, methyl isobutyl ketone. And the like; 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, ethylene glycol monomethyl ether; and mixtures thereof.

The composition ratio of the binder to the phosphor particles in the coating liquid varies depending on the characteristics of the intended radiation image conversion panel, the type of phosphor particles, etc., but is 1: 1 to 1:25 (weight ratio, but 1:25 is not included), and it is particularly preferable to select from the range of 1: 8 to 1:22 (weight ratio).

The coating liquid contains a dispersant for improving the dispersibility of the phosphor particles in the coating liquid.
Various additives such as a plasticizer for improving the binding force between the binder and the phosphor particles in the shaped phosphor layer may be mixed. Examples of dispersants used for such purpose 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, diphenyl phosphate; phthalic acid esters such as diethyl phthalate and dimethoxyethyl phthalate; ethyl phthalyl glycolate, butyl phthalyl butyl glycolate, etc. And a polyester of polyethylene glycol and an aliphatic dibasic acid, such as a polyester of triethylene glycol and adipic acid, a polyester of diethylene glycol and succinic acid, and the like.

The coating solution containing the phosphor particles and the 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 performed by using an ordinary coating means such as a doctor blade, a roll coater or a knife coater. Then, the formed coating film is gradually heated and dried to complete the formation of the phosphor layer on the support. The layer 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, etc.
20 μm to 1 mm. However, this layer thickness is 50 to 500 μm
Is preferred.

The phosphor-containing resin layer does not necessarily have to be formed by directly applying the coating liquid on the support as described above, and for example, a sheet such as a glass plate, a metal plate, a plastic sheet or the like may be separately formed. (Temporary support) A coating solution is applied on the support and dried to form a phosphor layer, and then the support is pressed onto the support or an adhesive is used to separate the support and the phosphor layer. You may join.

The support used in the present invention can be arbitrarily selected from various materials used as the support of the intensifying screen in the conventional radiographic method. 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, ordinary paper, baryta paper, resin coat. Examples thereof include paper, pigment paper containing a pigment such as titanium dioxide, and paper sized with polyvinyl alcohol. However, in consideration of the characteristics and handling of the radiation image storage panel as an information recording material, a particularly preferable 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 dioxide. The former is a support suitable for a radiation image conversion panel of high sharpness type, and the latter is a support suitable for a radiation image conversion panel of high sensitivity type.

In the known radiation image conversion panel, in order to strengthen the bond between the support and the phosphor layer, or to improve the sensitivity or the image quality as the radiation image conversion panel, the side where the phosphor layer is provided is provided. A high molecular substance such as gelatin is applied to the surface of the support to form an adhesion imparting layer,
Alternatively, 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 is also provided. The support used in the present invention can also be provided with these various layers, and their configuration can be arbitrarily selected according to the desired purpose and application of the radiation image conversion panel.

Further, as described in Japanese Patent Application No. 57-82431, for the purpose of improving the sharpness of the image obtained, the surface of the support on the phosphor layer side (the phosphor layer of the support is If the adhesion-imparting layer, the light-reflecting layer, or the light-absorbing layer is provided on the side surface, it means that surface).
In addition, irregularities may be formed.

The porosity of the phosphor-containing resin layer formed on the support as described above can be theoretically determined by the following formula (I).

[0047] (However, V: total volume of phosphor layer Vair: air volume in phosphor layer A: total weight of phosphor ρ _x : density of phosphor ρ _y : density of binder ρ _air : density of _air a: fluorescence Body weight b: weight of binder)

In equation (I), since ρair is ˜0, equation (I) can be approximately represented by the following equation (II).

[0049] (However, V, Vair, A, ρ _x , ρ _y , a, and b
Is the same as the formula (I))

The porosity of the phosphor-containing resin layer of the present invention was calculated by the above formula (II). As an example, the formation of a phosphor-containing resin layer consisting of a divalent europium-activated barium fluorobromide phosphor and a mixture of linear polyester and nitrocellulose as a binder on a support is usually carried out as described above. It is carried out by the coating method under normal pressure, and specifically, for example, as follows.

A mixture of a linear polyester and nitrocellulose and particles of a divalent europium-activated barium fluorobromide phosphor (BaFBr: Eu ²⁺ ) were mixed in a composition ratio of 1:20 (weight ratio). Mix well in methyl ethyl ketone using a propeller mixer to prepare a coating solution with a viscosity of 30 PS (25 ° C). After uniformly coating this coating solution on polyethylene terephthalate (support) using a doctor blade, put it in a dryer and gradually increase the temperature inside the container from 25 ° C to 100 ° C to dry the coating film. By doing so, a phosphor-containing resin layer is formed on the support.

The void ratio of the phosphor-containing resin layer having the composition ratio of the binder and the phosphor thus formed of 1:20 is 24.6%.
Met. Further, the porosity of the phosphor-containing resin layer having a composition ratio of the binder and the phosphor formed by the same treatment as above except that the amount of the binder and the phosphor used is changed to 1:10,
It was 14.4%.

The above-mentioned phosphor-containing resin layer is a typical example of the phosphor layer formed by a usual coating method under normal pressure, and even if the kinds of binder, phosphor particles and solvent are changed,
The porosity of the obtained phosphor layer does not change significantly. In addition, in the calculation of the porosity of the formula (II), the amount of the additive added to the coating liquid is very small and can be ignored. The porosity of the phosphor layer is not significantly affected by changes in the coating conditions as long as it is within the range of coating operations that are normally performed.

Therefore, the largest factor that changes the porosity of the phosphor-containing resin layer is that the composition ratio of the binder to the phosphor [in the definition of the formula (II) is as is clear from the above formula (II). b: a, weight ratio]. As the ratio of the phosphor particles to the binder in the phosphor-containing resin layer increases, the average distance between the phosphor particles dispersed in the binder becomes shorter and voids are more likely to occur between them. Therefore, the porosity of the phosphor-containing resin layer tends to increase as the amount of phosphor increases.

In the method of manufacturing the radiation image storage panel of the present invention, next, a part of the air mixed in the phosphor layer is removed to reduce the voids. The reduction of the voids is performed, for example, by compressing the phosphor layer.

The compression treatment of the phosphor layer is generally 50 to 1500 kg.
The heating is carried out at a pressure in the range of / cm ² at a temperature in the range of room temperature to the melting point of the phosphor layer. Compression time is 30 seconds ~
It is preferably in the range of 5 minutes. The preferred pressure is 10
0 to 1000 kg / cm ² , particularly preferred pressure is 300 to 700 k
It is g / cm ² . The preferred temperature is 50 to 120 ° C., although it depends on the binder used.

Examples of the compressing device used for the compressing process of the present invention include calender rolls, hot presses and the like generally known. For example, the compression treatment with a calendar roll is performed by passing a sheet composed of a support and a phosphor layer at a constant speed between rollers heated to a constant temperature. The compression treatment by hot pressing is performed by fixing the sheet between two metal plates heated to a constant temperature and then applying a constant pressure from both sides for a certain period of time. However, the compression device used in the present invention is not limited to these, and any device can be used as long as it can compress the sheet while heating.

For example, when the phosphor-containing resin thin film formed on the temporary support is subjected to compression treatment, it may be performed before the thin film is attached 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 the temporary support is compressed, and then the compressed phosphor-containing resin thin film is converted into a radiation image. It is attached to the support of the panel.

In a normal radiation image conversion panel, the surface of the phosphor layer on the side opposite to the side in contact with the support is
A transparent protective film is provided for physically and chemically protecting the phosphor layer. It is preferable to install such a transparent protective film also in the radiation image storage panel of the present invention.

The transparent protective film is, for example, a cellulose derivative such as cellulose acetate or nitrocellulose; or polymethyl methacrylate, polyvinyl butyral,
A method of applying a solution prepared by dissolving a transparent polymer substance such as polyvinyl formal, polycarbonate, polyvinyl acetate, and a synthetic polymer substance such as vinyl chloride / vinyl acetate copolymer in a suitable solvent to the surface of the phosphor layer Can be formed by. Alternatively, it can also be formed by a method of adhering a transparent thin film separately formed from polyethylene terephthalate, polyethylene, vinylidene chloride, polyamide or the like to the surface of the phosphor layer with an appropriate 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 storage panel of the present invention manufactured by the method represented by the above-mentioned method (the composition ratio of the binder and the stimulable phosphor is 1: 1).
To 1:25, but not including 1:25), the porosity is not more than 85% of the porosity of the phosphor-containing resin layer having the composition ratio formed by the coating method under normal atmospheric pressure. .

By reducing the porosity of the phosphor-containing resin in the radiation image conversion panel as described above, the density of the phosphor in the phosphor layer is increased, and therefore, when the amount of phosphor used is constant, the phosphor layer is The image is thinned and therefore the sharpness of the resulting image is significantly improved without a reduction in sensitivity.

Next, examples and comparative examples of the present invention will be described. However, each of these examples does not limit the present invention.

[0064]

【Example】

Example 1 Particles of a mixture (binder) of a linear polyester resin and nitrocellulose having a nitrification degree of 11.5% and a stimulable divalent europium-activated barium fluorobromide phosphor (BaFBr: Eu ²⁺ ). And
Mix at a weight composition ratio of 1:20, add methyl ethyl ketone, then thoroughly stir and mix using a propeller mixer,
A coating liquid having phosphor particles uniformly dispersed and a viscosity of 30 PS (25 ° C.) was prepared. Next, a polyethylene terephthalate sheet containing titanium dioxide (support, thickness: 250μ
m) was placed horizontally on a glass plate, and the coating solution was uniformly applied onto this support using a doctor blade. After the coating, the support on which the coating film was formed was placed in a dryer, and the temperature inside the dryer was gradually raised from 25 ° C to 100 ° C to dry the coating film. Thus, a sheet composed of the support and the fluorescent layer having a layer thickness of about 300 μm provided on the support was obtained.

Then, a sheet consisting of the support and the phosphor layer formed on one side thereof was placed on a sheet using a calendar roll.
Compressed at a pressure of 620 kg / cm ² and a temperature of 100 ° C.

Then, a transparent film of polyethylene terephthalate (thickness: 12 μm is formed on the compressed phosphor layer.
m, the one to which a polyester-based adhesive is applied) with the adhesive layer side facing downward to form a transparent protective film, which is composed of a support, a phosphor layer, and a transparent protective film. Manufactured radiation image conversion panel.

Example 2 The same sheet as the sheet made of the support produced in Example 1 and the phosphor layer provided on the support was used at 420 kg / c.
By carrying out the same treatments as in the method of Example 1, except that compression was carried out at a pressure of m ² and a temperature of 100 ° C.,
A radiation image conversion panel composed of a phosphor layer and a transparent protective film was manufactured.

Example 3 The same sheet as the sheet made of the support produced in Example 1 and the phosphor layer provided on the support was used at 620 kg / c.
A radiation image conversion panel composed of a support, a phosphor layer, and a transparent protective film was obtained by performing the same treatment as in Example 1 except that compression was performed at a pressure of m ² and a temperature of 80 ° C. Manufactured.

Example 4 The same sheet as the sheet made of the support produced in Example 1 and the phosphor layer provided on the support was used at 420 kg / c.
A radiation image conversion panel composed of a support, a phosphor layer, and a transparent protective film was obtained by performing the same treatment as in Example 1 except that compression was performed at a pressure of m ² and a temperature of 80 ° C. Manufactured.

Comparative Example 1 Similar to the method of Example 1 except that the same sheet as the sheet made of the support manufactured in Example 1 and the phosphor layer provided on the support is not compressed. By performing various treatments, a radiation image conversion panel including a support, a phosphor layer, and a transparent protective film was manufactured.

The measured volume and weight of the phosphor layer of each radiation image conversion panel produced as described above, the density of the phosphor used (5.1 g / cm ³ ) and the density of the binder (1.258 g) / Cm ³ ) and the porosity of the phosphor-containing resin layer was calculated by the formula (II).

The results obtained for each phosphor-containing resin layer are shown in Table 1.

[0073]

Each of the radiation image conversion panels manufactured as described above was evaluated by the image sharpness test described below. That is, the tube voltage is applied to the radiation image conversion panel.
After irradiating 80KVp X-ray, He-Ne laser light (632.8
nm) to excite the phosphor, receive the stimulated emission emitted from the phosphor layer, convert it into an electric signal, and reproduce it as an image using an image reproducing device to display the image on the display device. Obtained. The modulation transfer function (MTF) of the obtained image was measured.

The obtained results are shown together in the form of a graph in FIG.

In FIG. 1, A is the relationship between the spatial frequency and sharpness (MTF value) in the radiation image conversion panel of Example 1, and B is the spatial frequency and sharpness in the radiation image conversion panel of Comparative Example 1 ( MTF value).

The results obtained for each radiation image conversion panel (at a spatial frequency of 2 cycles / mm)
The MTF value) is shown in Table 2.

[0078]

Example 5 A mixture (binder) of a linear polyester resin and nitrocellulose having a nitrification degree of 11.5% and a stimulable divalent europium-activated barium fluorobromide phosphor (BaFBr: Eu ^2+). ) Particles and
A radiation image conversion panel composed of a support, a phosphor layer, and a transparent protective film was produced by performing the same treatment as in Example 1 except that the mixture was mixed at a weight composition ratio of 1:10. .

Example 6 The same sheet as the sheet made of the support produced in Example 5 and the phosphor layer provided on the support was used at 420 kg / c.
A radiation image conversion panel composed of a support, a phosphor layer, and a transparent protective film was obtained by performing the same treatment as in the method of Example 5 except that compression was performed at a pressure of m ² and a temperature of 100 ° C. Manufactured.

Example 7 The same sheet as the sheet made of the support produced in Example 5 and the phosphor layer provided on the support was used at 620 kg / c.
A radiation image conversion panel composed of a support, a phosphor layer, and a transparent protective film was obtained by performing the same treatment as in the method of Example 5 except that compression was performed at a pressure of m ² and a temperature of 80 ° C. Manufactured.

Example 8 The same sheet as the sheet made of the support produced in Example 5 and the phosphor layer provided on the support was used at 420 kg / c.
A radiation image conversion panel composed of a support, a phosphor layer, and a transparent protective film was obtained by performing the same treatment as in the method of Example 5 except that compression was performed at a pressure of m ² and a temperature of 80 ° C. Manufactured.

Comparative Example 2 Similar to the method of Example 5 except that the same sheet as the sheet made of the support manufactured in Example 5 and the phosphor layer provided on the support is not compressed. By performing various treatments, a radiation image conversion panel including a support, a phosphor layer, and a transparent protective film was manufactured.

The porosity of the phosphor-containing resin layer of each radiation image conversion panel manufactured as described above was calculated and calculated by the same method as described above.

The results obtained for each phosphor-containing resin layer are shown in Table 3.

[0086]

Each radiation image conversion panel manufactured as described above was evaluated by the image sharpness test.

Results obtained for each radiation image conversion panel (MTF value at spatial frequency 2 cycles / mm)
Is shown in Table 4.

[0089]

[Brief description of drawings]

FIG. 1 is a modulation transfer function (MT) of an image obtained by using the radiation image conversion panels manufactured in Example 1 and Comparative Example 1.
It is a graph of F). In FIG. 1, A is the relationship between the spatial frequency and the 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 radiation image conversion panel of Comparative Example 1. Spatial frequency and sharpness (MTF) in (radiation image conversion panel manufactured by ordinary coating method)
Value).

Continuation of the front page (56) References JP-A-56-74175 (JP, A) JP-A-55-12143 (JP, A) JOURNAL OF THE ELE CTROCHEMICAL SOCIEET Y, VOL. 122, NO. 8 (1975-8) (US) P. 1089-1092

Claims (5)

[Claims] 1. A composition comprising a support and a binder and a stimulable phosphor provided on the support in a composition ratio of 1: 1 to 1:25 (weight ratio, but not including 1:25). In a radiation image conversion panel substantially composed of a phosphor-containing resin layer in the range,
Radiation image characterized in that the porosity of the phosphor-containing resin layer has a value of 85% or less of the porosity of the phosphor-containing resin layer of the composition ratio formed by a coating method under normal atmospheric pressure. Conversion panel. 2. The radiation image conversion panel according to claim 1, wherein the stimulable phosphor is a divalent europium-activated alkaline earth metal fluoride halide phosphor. 3. The divalent europium-activated alkaline earth metal fluorohalide-based phosphor is a divalent europium-activated barium fluorobromide phosphor. The described radiation image conversion panel. 4. The radiation image conversion panel according to any one of claims 1 to 3, wherein the binder is a mixture of linear polyester and nitrocellulose. 5. A decrease in the porosity of the phosphor-containing resin layer,
The radiation image storage panel according to any one of claims 1 to 4, which is obtained by compressing the phosphor-containing resin layer.