JP2549913B2 - Radiation image conversion panel - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a radiation image conversion panel used for a radiation image conversion method using a stimulable phosphor.

[Technical Background and Prior Art of the Invention] As an alternative to the conventional radiographic method, for example, a radiation image conversion method using a stimulable phosphor as described in JP-A-55-12145 or the like is known. Are known. This method utilizes a radiation image conversion panel (also referred to as a stimulable phosphor sheet) containing a stimulable phosphor,
Radiation transmitted through the subject or emitted from the subject is absorbed by the stimulable phosphor of the panel, and then the stimulable phosphor is time-series by electromagnetic waves (excitation light) such as visible light and infrared rays. Upon excitation, the radiation energy accumulated in the stimulable phosphor is emitted as fluorescence (stimulated luminescence light), and the fluorescence is photoelectrically read to obtain an electric signal, and the obtained electric signal is obtained. Based on this, the radiation image of the subject or the subject is reproduced as a visible image.

According to this radiographic image conversion method, it is possible to obtain a radiographic image with a large amount of information at a much lower exposure dose compared to the radiographic method using a combination of a conventional radiographic film and an intensifying screen. There is an advantage that you can.
Therefore, this method is very useful especially in direct medical radiography such as X-ray radiography for medical diagnosis.

The radiation image conversion panel used in the radiation image conversion method has, as a basic structure, a support and a stimulable phosphor layer provided on one surface thereof. In addition, when the phosphor layer is self-supporting, a support is not always necessary. In addition, a transparent protective film is generally provided on the surface of the photostimulable phosphor layer opposite to the support (the surface not facing the support), and the phosphor layer is chemically treated. Protects against severe alteration or physical shock.

The stimulable phosphor layer is generally composed of a stimulable phosphor and a binder containing and supporting the stimulable phosphor in a dispersed state. The stimulable phosphor layer absorbs radiation such as X-ray and then emits excitation light. It has the property of exhibiting stimulated emission upon irradiation.
Therefore, the radiation transmitted through the subject or emitted from the subject is absorbed by the stimulable phosphor layer of the radiation image conversion panel in proportion to the radiation dose, and the radiation image of the subject or subject is radiated on the panel. It is formed as an accumulated image of energy. This accumulated image can be emitted as stimulated emission light by irradiating the excitation light,
By photoelectrically reading this stimulated emission light and converting it into an electric signal, it is possible to form an accumulated image of radiation energy.

The radiation image conversion method is a very advantageous image forming method as described above, but the radiation image conversion panel used in this method has high sensitivity as in the intensifying screen used in the conventional radiographic method. In addition, it is desired that the image gives a good image quality (sharpness, graininess, etc.).

The sensitivity of the radiation image conversion panel basically depends on the total stimulated emission amount of the stimulable phosphor contained in the panel, and this total emission amount depends not only on the emission brightness of the phosphor situation,
It also depends on the content of the phosphor in the phosphor layer. A large content of the phosphor also means a large absorption for radiation such as X-rays, so that higher sensitivity can be obtained and at the same time, image quality (particularly graininess) is improved. on the other hand,
In the case where the phosphor content in the phosphor layer is constant, the layer thickness can be reduced as the phosphor particles are more densely packed, so that the spread of excitation light due to scattering can be reduced. And a relatively high sharpness can be obtained.

The applicant of the present application, as one of the radiation image conversion panels having a phosphor layer densely packed with a phosphor, a radiation image conversion panel in which the porosity of the phosphor layer is reduced by compressing the phosphor layer. And its manufacturing method have already been applied (see JP-A-59-126299, JP-A-59-126300).

In the above radiation image conversion panel, the phosphor layer is compressed so that the density of the phosphors in the phosphor layer is higher than that of the radiation image conversion panels up to then. as a result,
Although this radiation image conversion panel had excellent sharpness, on the other hand, there was a problem that the phosphor was partially destroyed by the compression treatment, so that it could be rather deteriorated in terms of graininess. there were.

SUMMARY OF THE INVENTION It is also an object of the present invention to provide a radiation image conversion panel having excellent sharpness and excellent graininess.

The above object of the present invention is a support, and a radiation image conversion panel substantially constituted by a phosphor layer comprising a binder and a stimulable phosphor provided on the support, The filling rate of the phosphor in the phosphor layer is 70%.
And 10 wt% or more and 100 wt% of the binder
The following can be achieved by a radiation image conversion panel characterized by being a thermoplastic elastomer having a softening temperature or a melting point of 30 ° C. or higher and 150 ° C. or lower.

The radiation image conversion panel of the present invention, even if the filling rate of the phosphor by compression treatment is 70% or more, since the binder of the phosphor layer is made of a thermoplastic elastomer, during compression,
By heating the elastomer at a softening temperature or a temperature equal to or higher than the melting point, the degree of breakage of the phosphor can be reduced. In addition, a phosphor sheet made of a phosphor and a binder is prepared in advance, and the phosphor sheet is placed on a support and compressed at the same time as the softening temperature or melting point of the binder is set on the support. By doing so, it is possible to further prevent the phosphor from being damaged.

That is, at the time of compression, the phosphor crystal dispersed in the binder that is heated to the softening temperature or the melting point or higher is subjected to pressure with a certain degree of freedom. It can be oriented. Furthermore, pressure is applied in a state where the phosphor sheet is not fixed to the support, and when the phosphor sheet is installed on the support while being compressed, the pressure applied to the phosphor sheet acts to orient the phosphor crystals, and at the same time, If the phosphor sheet is fixed, it works to spread the sheet thinly even under the pressure that destroys the crystals. Further, in this case, as compared with the case where the phosphor sheet is pressed while being fixed on the support, a high phosphor packing rate can be obtained even when compressed with the same pressure.

 The preferred embodiments of the present invention are listed below.

(1) The thermoplastic elastomer is selected from polystyrene, polyolefin, polyurethane, polyester, polyamide, polybutadiene, ethylene vinyl acetate, polyvinyl chloride, natural rubber, fluororubber, polyisoprene, chlorinated polyethylene, styrene-butadiene rubber and silicone rubber. A radiation image conversion panel, which is at least one thermoplastic elastomer selected from the group consisting of:

(2) A radiation image conversion panel, wherein the binder is a 100% by weight thermoplastic elastomer.

[Configuration of the Invention] The radiation image storage panel of the present invention can be manufactured, for example, by the method described below.

In order to manufacture the radiation image storage panel of the present invention, a) a step of forming a phosphor sheet composed of a binder and a stimulable phosphor, b) placing the phosphor sheet on a support, and binding the binder. The step of adhering the phosphor sheet on a support while compressing it at a softening temperature or a temperature equal to or higher than the melting point is preferable.

 First, step a) will be described.

The phosphor sheet serving as the phosphor layer of the radiation image conversion panel was coated with a coating solution in which the stimulable phosphor was uniformly dispersed in a binder solution on a temporary support for forming the phosphor sheet, and dried. Thereafter, it can be manufactured by peeling off from the temporary support.

The phosphors used in the present invention will be described below.

The stimulable phosphor is a phosphor that emits stimulated emission when irradiated with excitation light after being irradiated with radiation as described above, but from a practical viewpoint, the wavelength is in the range of 400 to 900 nm. A phosphor that exhibits stimulated emission in the wavelength range of 300 to 500 nm by excitation light is desirable. Examples of the stimulable phosphor used in the radiation image conversion panel of the present invention include BaSo ₄ : AX described in JP-A-48-80487 and JP-A-48-80489. SrSO ₄ : AX
In phosphor represented, Li is described in _{JP-A-53-39277 2 B 4 O 7: Cu} ,
Ag, Li ₂ O (B described in JP-A-54-47883)
₂ O ₂ ) _x : Cu and Li ₂ O. (B ₂ O ₂ ) _x : Cu, Ag, SrS: Ce, described in U.S. Pat.
Sm, SrS: Eu, Sm, ThO 2: Er, and _{La 2 O 2 S: Eu,} Sm, are described in JP-A-55-12142 ZnS: Cu, Pb,
BaO.xAl ₂ O ₃ : Eu (where 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), which is described in JP-A-55-12143 (Ba _1-Xy , M
g _X , Ca _y ) FX: aEu ²⁺ (where X is at least one of Cl and Br, and x and y are 0 <x + y ≦ 0.
6, and xy ≠ 0, a is 10 ⁻⁶ ≦ a ≦ 5 × 10 ⁻² ), and LnOX: xA described in JP-A-55-12144 (where Ln is La, At least one of Y, Gd, and 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), described in JP-A-55-12145 (Ba _1-X , M ²⁺
_X ) FX: yA (where M ²⁺ is at least one of Mg, Ca, Sr, Zn, and Cd, X is at least one of Cl, Br, and I, 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), BaFX: xCe.y described in JP-A-55-84387.
M ^II FX · xA listed in the phosphor Sho 55-160078 discloses represented by A:
yLn [where M ^II is at least one of Ba, Ca, Sr, Mg, Zn, and Cd; A is BeO, MgO, CaO, SrO, BaO, Z
nO, Al ₂ O ₃ , Y ₂ O ₃ , La ₂ O ₃ , In ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , G
At least one of eO ₂ , SnO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , and ThO ₂ , Ln is Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb,
At least one of Er, Sm, and Gd, X is Cl, B
at least one of r and I, wherein x and y are respectively 5 × 10 ⁻⁵ ≦ x ≦ 0.5 and 0 <y ≦ 0.2]. No. 116777 (Ba _1-X , 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 kind of zirconium and suranium, and 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
Phosphor represented by a composition formula of In is] are described in _{JP-A-57-23673 (Ba 1-X, M} II
_X ) F ₂ · aBaX ₂ : yEu, zB [where M ^II is at least one of beryllium, magnesium, calcium, strontium, zinc, and cadmium, X is chlorine, bromine,
And at least one of iodine and a, x,
y and z are respectively 0.5 ≦ a ≦ 1.25, 0 ≦ x ≦ 1, 1
0 ⁻⁶ ≦ y ≦ 2 × 10 ⁻¹ , and 0 <z ≦ 2 × 10 ⁻¹ ]
Phosphor represented by the composition formula is described in _{JP-A-57-23675 (Ba 1-X, M} II
_X ) F ₂ aBaX ₂ : yEu, zA [where M ^II is at least one of beryllium, magnesium, calcium, strontium, zinc, and cadmium, X is chlorine, bromine,
And at least one of iodine and A is at least one of arsenic and silicon, and a, x, y and z are respectively 0.5 ≦ a ≦ 1.25, 0 ≦ x ≦ 1, 10 ⁻⁶ ≦ y ≦
2 × 10 ⁻¹ and 0 <z ≦ 5 × 10 ⁻¹ ], and M ^III OX: xCe described in JP-A-58-69281.
[However, M ^III is Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, E
at least one trivalent metal selected from the group consisting of r, 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 following composition formula: Ba _1-X M _{X / 2} described in JP-A-58-206678.
L _{X / 2} FX: _y Eu ²⁺ [where M is Li, Na, K, Rb, and C
represents at least one alkali metal selected from the group consisting of s; 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
.Ltoreq.x.ltoreq.0.5, y is 0 <y.ltoreq.0.1]. BaFX.xA: yE described in JP-A-59-27980.
u ^{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, y is 0 <y ≤ 0.1] xM ₃ (PO ₄ ) described in JP-A-59-38278
₂・ NX ₂ : yA, M ₃ (PO ₄ ) ₂ : yA and nReX ₃・ mAX ′ ₂ : xEu,
nReX ₃・ mAX ′ ₂ : xEu, ySm, M ^I X ・ aM ^II X ′ ₂・ bM ^III X ″ ₃ : c
A phosphor represented by A, BaFXxA: yE described in JP-A-59-47289.
u ²⁺ [wherein X is at least one halogen selected from the group consisting of Cl, Br, and I; A is a monovalent or divalent tetrafluorosilicic acid, hexafluorotitanic acid, and hexafluorozirconic acid; It is a calcined product of at least one compound selected from the group of hexafluoro compounds consisting of salts of valent metals; and x is 10 ⁻⁶ ≦ x ≦
0.1, y is 0 <y ≦ 0.1], a phosphor represented by the composition formula, BaFX.xNa described in JP-A-59-56479.
X ′: aEu ²⁺ [where X and X ′ are Cl, B
at least one of r and I, and x and a
Are 0 <x ≦ 2 and 0 <a ≦ 0.2, respectively, and the phosphor represented by the composition formula: M ^II FX.xNa described in JP-A-59-56480.
X ′: yEu ²⁺ : zA [where M ^II is at least one alkaline earth metal selected from the group consisting of Ba, Sr, and Ca; 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 1 is 0 <z ≦ 10 ⁻² ], the phosphor represented by the composition formula, M ^II FX.aM described in JP-A-59-75200.
^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, Na, K, R
b, and at least one alkali metal selected from the group consisting of Cs; M ′ ^II is at least one divalent metal selected from the group consisting of Be and Mg; M ^III is Al, G
a, In, and at least one trivalent metal selected from the group consisting of Tl; A is a metal oxide; X is Cl, Br,
X ', X ", and X are 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 ≦ 1
0 ^-2 and c are 0≤c≤10 ^-2 and a + b + c≥10 ^-6 ;
x is 0 <x ≦ 0.5 and y is 0 <y ≦ 0.2], the phosphor represented by the composition formula M ^II X ₂ · aM ^II described in JP-A-60-84381.
X ′ ₂ : xEu ²⁺ [where M ^II is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca; X and X ′ are selected from the group consisting of Cl, Br and I A stimulable phosphor represented by a composition formula of at least one halogen and X 、 X ′; and a is 0.1 ≦ a ≦ 10.0 and x is 0 <x ≦ 0.2. M ^II FX ・ aM ^I described in JP-A-60-101173
X ′ · xEu ²⁺ [wherein M ^II is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca; M ^I is at least one alkali metal selected from the group consisting of Rb and Cs X is at least one halogen selected from the group consisting of Cl, Br and I; X'is at least one halogen selected from the group consisting of F, Cl, Br and I; and a and x Each is 0
≦ a ≦ 4.0 and 0 <x ≦ stimulable phosphor represented by a composition formula of 0.2 and a], M ^I X are described in JP-A-62-25189: xBi [However, M ^I is Rb And at least one alkali metal selected from the group consisting of Cs; X is at least one halogen selected from the group consisting of Cl, Br, and I; and x is a number in the range 0 <x ≦ 0.2. ] A stimulable phosphor represented by the composition formula of

Further, M described in JP-A-60-84381 described above
^II X ₂・ aM ^II X ′ ₂ : xEu ²⁺ Stimulable phosphor contains the following additives in the following ratio per mole of M ^II X ₂・ aM ^II X ′ ₂ : Is also good.

JP bM ^I X that are described in 60-166379 JP "(where, M ^I is at least one alkali metal selected from the group consisting of Rb and Cs, X 'is F, Cl, Br and I At least one halogen selected from the group consisting of: and b is 0 <b ≦ 10.0);
BKX ″ · cMgX ₂ · dM ^III X described in Japanese Patent No. 1483
′ ₃ (where M ^III is at least one trivalent metal selected from the group consisting of Sc, Y, La, Gd and Lu,
X ″, X and X ′ are all F, Cl, Br and I
Is at least one halogen selected from the group consisting of, and b, c and d are each 0 ≦ b ≦ 2.0,
0 ≦ c ≦ 2.0, 0 ≦ d ≦ 2.0, and 2 × 10 ⁻⁵ ≦ b
+ C + d); yB described in JP-A-60-228592 (where y is 2 × 10 ⁻⁴ ≦ y ≦ 2 × 10 ⁻¹ ); JP-A-60-228593. BA as described (where A is at least one oxide selected from the group consisting of SiO ₂ and P ₂ O ₅ , and b is 10 ⁻⁴ ≦ b ≦ 2 ×
10 ^-1 is); bSiO that are described in JP 61-120883 Laid (where, b is 0 <b ≦ 3 is a × 10 ^-2); described in JP-A No. 61-120885 Laid BSnX ″ ₂ (where X ″ is at least one halogen selected from the group consisting of F, Cl, Br and I, and b is 0 <b ≦
10 a ^-3); JP 61-235486 discloses to have bCsX "· cSnX _{2 (however,} X" which is described and X are each F, Cl, at least one selected from the group consisting of Br and I Halogen, and b and c are 0 <b ≦ 10.0 and 10 ⁻⁶ ≦ c ≦ 2 × 10 ⁻² respectively);
And bCsX ″ described in JP-A No. 61-235487.
YLn ³⁺ (where X ″ is at least one halogen selected from the group consisting of F, Cl, Br and I, and Ln is
Sc, Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb
And at least one rare earth element selected from the group consisting of Lu, and b and y are each 0 <b ≦
10.0 and 10 ⁻⁶ ≦ y ≦ 1.8 × 10 ⁻¹ ).

Among the above stimulable phosphors, a divalent europium-activated alkaline earth metal halide-based phosphor and a cerium-activated rare earth oxyhalide-based phosphor are particularly preferable because they exhibit high-luminance stimulable emission. However, the stimulable phosphor used in the present invention is not limited to the above-mentioned phosphor, and may be any phosphor that exhibits stimulated emission when irradiated with excitation light after irradiation with radiation. It may be.

The stimulable phosphor and the binder as described above are added to an appropriate solvent and mixed sufficiently to prepare a coating solution in which the stimulable phosphor is uniformly dispersed in the binder solution.

As the binder, a thermoplastic elastomer having a softening temperature or a melting point of 30 ° C. to 150 ° C. is used in an amount of 10% by weight or more. Since the thermoplastic elastomer has elasticity at room temperature and becomes fluid when heated, it is possible to prevent the phosphor from being damaged by the pressure during compression. Examples of thermoplastic elastomers include polystyrene, polyolefin, polyurethane, polyester, polyamide, polybutadiene, ethylene vinyl acetate, polyvinyl chloride, natural rubber,
Fluorine rubber, polyisoprene, chlorinated polyethylene, styrene-butadiene rubber, silicone rubber and the like can be mentioned.

The component ratio of the thermoplastic elastomer in the binder can obtain the effect of the present invention as long as it is 10% by weight or more and 100% by weight or less as described above, but the binder is as many thermoplastic elastomers as possible, particularly 100% by weight. % Thermoplastic elastomer.

Examples of the solvent for preparing the coating liquid include lower alcohols such as methanol, ethanol, n-propanol and n-butanol; hydrocarbons containing chlorine atoms such as methylene chloride and ethylene chloride; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone. Esters of lower fatty acids such as methyl acetate, ethyl acetate and butyl acetate with lower alcohols; ethers such as dioxane, ethylene glycol monoethyl ether and ethylene glycol monomethyl ether; and mixtures thereof.

The mixing ratio between the binder and the stimulable phosphor in the coating solution is
Depending on the characteristics of the intended radiation image conversion panel, the type of phosphor, etc., generally, the mixing ratio of the binder and the phosphor is selected from the range of 1: 1 to 1: 100 (weight ratio), and It is particularly preferable to select from the range of 1: 8 to 1:40 (weight ratio).

The coating liquid contains a dispersant for improving the dispersibility of the phosphor in the coating liquid, and also for improving the binding 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:
Examples include phthalic acid, stearic acid, caproic acid, and lipophilic surfactants. 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 liquid containing the phosphor and the binder prepared as described above is then uniformly applied to the surface of the temporary support for sheet formation to form a coating film of the coating liquid. This coating operation can be performed by using an ordinary coating means such as a doctor blade, a roll coater or a knife coater.

The temporary support is, for example, a glass, a metal plate, various materials used as a support for an intensifying screen (or an intensifying screen) in a conventional radiographic method, or a support for a radiation image conversion panel. Can be arbitrarily selected from known materials. Examples of such materials include films of plastic substances such as cellulose acetate, polyester, polyethylene terephthalate, polyamide, polyimide, triacetate, polycarbonate, metal sheets such as aluminum foil, aluminum alloy foil, ordinary paper, baryta paper, resin. Examples thereof include coated paper, pigment paper containing a pigment such as titanium dioxide, paper sized with polyvinyl alcohol, etc., and plates or sheets of ceramics such as alumina, zirconia, magnesia, and titania.

A coating solution for forming a phosphor layer is applied onto a temporary support, dried, and then peeled from the temporary support to obtain a phosphor sheet which will be a phosphor layer of a radiation image conversion panel. Therefore, it is preferable to apply a release agent on the surface of the temporary support in advance so that the formed phosphor sheet can be easily peeled off from the temporary support.

 Next, step b) will be described.

First, apart from the phosphor sheet formed as described above,
A support for the radiation image conversion panel is prepared. This support can be arbitrarily selected from the same material as the temporary support used when forming the phosphor sheet.

In a known radiation image conversion panel, 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, graininess) of the radiation image conversion panel. The surface of the side support is coated with a polymer substance such as gelatin to form an adhesion-imparting layer, or a light-reflecting layer made of a light-reflecting substance such as titanium dioxide, or a light-absorbing substance made of a light absorbing substance such as carbon black. It is known to provide an absorbing layer and the like.
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 JP-A-58-200200, the surface of the support on the phosphor layer side (the surface of the support on the phosphor layer side) is used for the purpose of improving the sharpness of the obtained image. When an adhesiveness-imparting layer, a light-reflecting layer, a light-absorbing layer, or the like is provided, it means the surface thereof).

The phosphor sheet obtained in step a) is placed on a support and adhered to the support while being compressed at the softening temperature or the melting point of the binder or higher.

In this way, by compressing the phosphor sheet without previously fixing it on the support, the sheet can be spread thinly,
Not only can the phosphor be prevented from being damaged, but a higher phosphor packing rate can be obtained even with the same pressure as compared with the case where the sheet is fixed and pressed.

Examples of the compression device used for the compression treatment of the present invention include commonly known ones such as a calender roll and a hot press. For example, the compression treatment with a calender roll is carried out by placing the phosphor sheet obtained in step a) on a support and passing it at a constant speed between rollers heated to the softening temperature or melting point or higher of the binder. . However, the compression device used in the present invention is not limited to these,
Any material may be used as long as it can compress the sheet while heating.

The pressure during compression is generally 50 kgw / cm ² or more.

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

(However, V: total volume of phosphor layer Vair: air volume in phosphor layer A: total weight of phosphor layer ρ _X : density of phosphor ρ _y : density of binder ρ air: density of air a: fluorescence Weight of body b: Weight of binder) In the formula (I), since ρair is almost 0, the formula (I) can be approximately represented by the following formula (II).

(However, the definitions of V, Vair, A, ρ _X , ρ _y , a, and b are the same as those in the formula (I).) In the present invention, the porosity of the phosphor layer is calculated by the formula (II). I asked.

Further, the filling rate of the phosphor can be obtained by the following formula (III).

(However, the definitions of V, Vair, A, ρ _X , ρ _y , a, and b are the same as those in the formula (I).) In a normal radiation image conversion panel, as described above, the side in contact with the support is A transparent protective film for physically and chemically protecting the phosphor layer is provided on the surface of the phosphor layer on the opposite side. 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 may be, for example, a cellulose derivative such as cellulose acetate or nitrocellulose; or a transparent polymer material such as polymethylmethacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyvinyl acetate, vinyl chloride / vinyl acetate copolymer. It can be formed by a method in which a solution prepared by dissolving a high-molecular substance in a suitable solvent is applied to the surface of the phosphor layer. Alternatively, polyethylene terephthalate,
A plastic sheet made of polyethylene naphthalate, polyethylene, polyvinylidene chloride, polyamide, etc .; and a protective film forming sheet such as a transparent glass plate are separately formed and adhered to the surface of the phosphor layer by using an appropriate adhesive. It can also be formed by the method of.

 The thickness of the protective film is generally in the range of 0.1 to 20 μm.

Furthermore, in order to improve the sharpness of the obtained image,
A colored layer that absorbs excitation light but does not absorb stimulated emission light may be added to at least one of the above layers (see JP-B-59-23400).

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

[Example 1] As a coating solution for forming a phosphor sheet, phosphor: BaFBr _0.9 I _0.1 : Eu ²⁺ ... 200 g Binder: Polyurethane (Sumitomo Bayer Urethane Co., Ltd. Desmolac TPKL-5
2625 [solid content 40%], softening temperature 45 ° C) …… 22.5g Yellowing inhibitor: Epoxy resin (Eikaka Shell Epoxy Co., Ltd. Epicoat 1001) …… 1.0g of methyl ethyl ketone and 2-propanol 1: 1 Add to the mixed solvent and disperse with a propeller mixer to obtain a viscosity of 30.
A coating solution of PS (25 ° C.) was prepared (binder / phosphor ratio = 1 /
20). This was applied onto polyethylene terephthalate (temporary support, thickness 180 μm) coated with a silicone-based release agent, dried and then peeled from the temporary support to form a phosphor sheet.

On the other hand, as a coating liquid for forming the light reflecting layer, BaFBr (containing 90% of particles having a particle diameter in the range of 1 to 5 μm) ...
… 214 g Soft acrylic resin solid content …… 25.7 g Epoxy resin …… 10.7 g Nitrocellulose (nitrification degree 11.5%, solid content 10% by weight)…
64 g was added to methyl ethyl ketone and dispersed by a propeller mixer to prepare a dispersion liquid having a viscosity of 25 to 35 PS (25 ° C.).

Separately, as a coating liquid for forming an undercoat layer, soft acrylic resin solid content ...... 90 g nitrocellulose ...... 50 g is added to methyl ethyl ketone, dispersed and mixed to give a viscosity of 3
A dispersion of ~ 6PS (25 ° C) was prepared.

A 300 μm thick polyethylene terephthalate (support) is placed horizontally on a glass plate, and the above undercoat layer forming coating solution is uniformly applied on the support using a doctor blade, and then gradually from 25 ° C to 100 ° C. The coating film was dried by elevating the temperature to form an undercoat layer on the support (coating film thickness: 15 μm). Further, the above-mentioned coating solution for forming a light reflection layer was applied (thickness of the coating film: 60 μm), and dried similarly to form an undercoat layer and a light reflection layer on the support. The phosphor sheet prepared first was placed on this, and compression was performed.

The compression was continuously performed using a calender roll at a pressure of 400 Kgw / cm ² and a temperature of 80 ° C. With this compression,
The phosphor sheet and the light-reflecting layer on the support were completely fused.

After this compression, a transparent protective film was formed by adhering a transparent polyethylene terephthalate film (thickness 10 μm) coated with a polyester adhesive on one side with the adhesive side facing down.

As described above, a radiation image conversion panel composed of the support, the undercoat layer, the light reflection layer, the phosphor layer, and the transparent protective film was manufactured.

Example 2 In the same manner as in Example 1 except that the pressure at the time of compression was 600 Kgw / cm ² , the support, the undercoat layer, the light reflection layer, the phosphor layer, and the transparent protective film were formed. A constructed radiation image conversion panel was produced.

[Comparative Example 1] After forming an undercoat layer in the same manner as in Example 1, a coating liquid for forming a reflective layer was applied, and before the coating film was dried,
The phosphor layer-forming coating liquid was subsequently applied thereon. The temperature was gradually raised from 25 ° C. to 100 ° C. and drying was performed to form a sheet comprising a support, an undercoat layer, a light reflection layer, and a phosphor layer. Next, this sheet was compressed using a calender roll in the same manner as in Example 1 at a pressure of 400 Kg / cm ² and a temperature of 80 ° C. Further, a protective film was provided by the same method as in Example 1, and the support, the undercoat layer, the light reflection layer, the phosphor layer,
A radiation image conversion panel composed of a transparent protective film was manufactured.

[Comparative Example 2] In Comparative Example 1, the support, undercoat layer, light reflecting layer, phosphor layer, and transparent protective film were prepared in the same manner as in Comparative Example 1 except that the pressure during compression was 600 Kgw / cm ^2. A constructed radiation image conversion panel was produced.

[Comparative Example 3] In Comparative Example 1, a radiation image conversion comprising a support, an undercoat layer, a light reflection layer, a phosphor layer, and a transparent protective film was carried out in the same manner as Comparative Example 1 except that no compression was performed. The panel was manufactured.

Phosphor filling rate and porosity of the radiation image conversion panel phosphor layer In the phosphor layer of each of the radiation image conversion panels of Examples and Comparative Examples produced as described above, the phosphor filling rate and the porosity are defined as (II ) And equation (III).
However, the density of the phosphor is 5.1 g / cm ³ and the density of the binder is 1.
It is 14 g / cm ³ .

 The results are shown in Table 1.

As is clear from Table 1, the radiation image storage panel of the present invention has a higher phosphor packing rate and a lower porosity than the radiation image storage panel compressed at the same pressure. I understand.

Evaluation of Image Quality of Radiation Image Conversion Panel The image quality of each radiation image conversion panel manufactured as described above was evaluated by the method described below. That is, the radiation image conversion panel is irradiated with X-rays with a tube voltage of 80 KVp, then scanned with He-Ne laser light (632.8 nm) to excite the phosphor, and the stimulated emission emitted from the phosphor layer is received. Then, it was converted into an electric signal, which was reproduced as an image by the image reproducing device to obtain an image on the display device. Modulation transfer function (MTF) of the obtained image (spatial frequency: 2 cycles /
mm), and the granularity (RMS) at a dose of 0.1 mR was measured.

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

Figure 1 shows the vertical axis with sharpness (spatial frequency 2 cycles / m
The MTF value at m) is taken, and the higher the plot, the higher the sharpness. The horizontal axis indicates the graininess, and the more plotted to the left, the better the graininess.

As is apparent from FIG. 1, the radiation image storage panel of the present invention has a slight improvement in sharpness and a large improvement in graininess as compared with the panel of Comparative Example compressed at the same pressure. I know what I'm doing.

[Brief description of drawings]

FIG. 1 is a graph showing the image quality of the radiation image conversion panels according to the example and the comparative example.

Claims (1)

(57) [Claims] 1. A radiation image conversion panel substantially composed of a support and a phosphor layer comprising a binder and a stimulable phosphor provided on the support, wherein the phosphor layer. The filling rate of the phosphor is 70% or more, and 10% by weight or more and 100% by weight or less of the binder is 30 ° C. or more and 150% or more.
A radiation image conversion panel, which is a thermoplastic elastomer having a softening temperature or a melting point of ℃ or less.