JPS6319600A - Radiation image conversion panel and manufacture thereof - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a radiation image conversion panel used in a radiation image conversion method using a stimulable phosphor and a method for manufacturing the same.

[Technical Background of the Invention] Conventionally, a combination of a radiographic film having an emulsion layer made of a silver salt photosensitive material and an intensifying screen is used as a method for obtaining a radiographic image. A so-called radiographic method is used. Recently, attention has been paid to a radiation image conversion method using a stimulable phosphor, as described in, for example, Japanese Unexamined Patent Publication No. 55-1214S as an alternative to the radiographic method. The radiation image conversion method is
It uses a radiation image conversion panel (stimulable phosphor sheet) containing a stimulable phosphor, and the radiation transmitted through the subject or the radiation emitted from the subject is converted into the stimulable phosphor of the panel. By absorbing the stimulable phosphor and then exciting the stimulable phosphor in a time-series manner with electromagnetic waves (excitation light) such as visible light or infrared rays, the radiation energy stored in the stimulable phosphor is released into the phosphor. This fluorescence is emitted as (stimulated luminescence), and this fluorescence is read photoelectrically to obtain an electrical signal, and the obtained electrical signal is converted into an image.

This radiation image conversion method has the advantage that it is possible to obtain a radiation image with a rich amount of information with a much lower exposure dose than when using conventional radiography. Therefore, this method is especially useful for X-rays intended for medical diagnosis.
It has extremely high utility value in direct medical radiography such as g-A shadows.

Radiographic image conversion parameters used in the radiographic image conversion method ・
The basic structure of the flannel is a support and a phosphor layer provided on one side of the support. Note that the surface of the phosphor layer opposite to the support (the surface not facing the support) is generally provided with a transparent aS made of polymer ``PIJ'', which protects the phosphor. It protects the layer from chemical alteration or physical impact.

The phosphor layer is composed of a stimulable phosphor and a binder containing and supporting the stimulable phosphor in a dispersed state.
After absorbing radiation such as radiation.

It has the property of emitting light (stimulated luminescence) when irradiated with electromagnetic waves (excitation light) such as visible light and infrared rays. Therefore, the radiation transmitted through the subject or emitted from the subject is absorbed by the phosphor layer of the radiation image conversion panel in proportion to the amount of radiation, and the radiation image of the subject or subject is displayed on the radiation image conversion panel. is formed as an accumulated image of radiation energy. This Na image can be emitted as stimulated luminescence by time-series excitation with the electromagnetic waves mentioned above, and by photoelectrically reading this stimulated luminescence and converting it into an electrical signal, an image of the accumulation of radiation energy can be obtained. To become or to become usable.

The radiation image conversion method is a very advantageous image forming method as mentioned above, and the radiation image conversion panel used in this method is similar to the intensifying screen used in conventional radiography.
It is desirable that the image quality be high and provide images with excellent image quality (sharpness, graininess, etc.). In particular, when applying a radiation image conversion method to medical radiography, it is necessary to reduce the exposure dose to the human body and obtain more information, so the radiation image conversion panel used in the method only has a high sensitivity. High is desirable.

The sensitivity of a radiation image conversion panel basically depends on the total amount of stimulated luminescence of the stimulable phosphors contained in the panel, and this total amount of luminescence depends not only on the luminescence brightness of the stimulable phosphors themselves. , it also varies depending on the content of the phosphor in the phosphor layer. A high content of phosphor also increases absorption of radiation such as X-rays, resulting in higher sensitivity and at the same time improved image quality (particularly graininess). On the other hand, if the content of phosphor in the phosphor layer is constant, the more densely packed the phosphor particles are, the thinner the layer thickness will be, which will reduce the loss of excitation light due to scattering. Relatively high sensitivity can be obtained, and at the same time, images with good image quality can be obtained.

To form a phosphor layer in a radiation image storage panel, generally, a coating solution is prepared by adding photostimulable phosphor particles and a binder to a suitable solvent, and this coating solution is applied using a conventional coating method.
For example, this is carried out by directly applying the coating onto a support or another sheet using a doctor blade, roll coater, etc., and then drying it. The relative density (volume ratio occupied by the stimulable phosphor in the phosphor layer) of the phosphor layer made of the binder containing and supporting the stimulable phosphor thus obtained is limited to a maximum of about 60%. . Therefore, in order to improve the sensitivity using this normal coating method, there is a method of increasing the absolute amount of phosphor by increasing the thickness of the phosphor layer, but this method does not improve the image quality (g sharpness) of the image. The problem is that it causes a decline. For this reason, it is desirable that the thickness of the phosphor layer of the panel be within a certain appropriate range and that the relative density of the phosphor layer be high.

As a method of increasing the amount of phosphor in the phosphor layer (improving the relative density of the phosphor layer) without increasing the thickness of the phosphor layer, for example, compression means such as a calendar roll or a hot press can be used. A method of compressing a phosphor layer (or a phosphor layer and a support) using
Publication No. 300).

However, although the relative density of the phosphor layer formed using the above method increases, allowing more phosphor particles to exist in a phosphor layer of a given thickness, the compression reduces the phosphor density. This creates strain in the body itself, which tends to reduce sensitivity (pressure desensitization).

Note that a method of forming the phosphor layer as a layer consisting only of a stimulable phosphor without a binder is already known. For example, US EF Pat. The written amendment dated September 11, 2013 discloses a method of forming a phosphor layer using a firing method. However, all of these merely suggest that a hot press method or a firing method can be used.

[Summary of the Invention] An object of the present invention is to provide a radiation image storage panel with improved sensitivity and a method for manufacturing the same.

The above object is to provide a radiation image conversion panel having a support and a phosphor layer made of a stimulable phosphor provided thereon, in which the phosphor layer is formed from a sintered stimulable phosphor. This can be achieved by the radiation image conversion panel of the present invention, which is characterized in that the relative density of the phosphor layer is 70% or more.

Further, the above object is to form a phosphor layer containing a stimulable phosphor in a method for manufacturing a radiation image conversion panel having a support and a phosphor layer made of a stimulable phosphor provided thereon. This can be achieved by the method for manufacturing a radiation image storage panel of the present invention, which is characterized in that a phosphor layer is formed by molding a material into a sheet shape and then sintering the molded product.

In the present invention, the relative density of the phosphor layer refers to the ratio of the volume occupied by the phosphor to the total volume of the phosphor layer.

In the present invention, the phosphor layer of the radiation image conversion panel is composed only of sintered stimulable phosphor, and the relative density of the phosphor layer is increased to 70% or more to improve the filling state of the phosphor in the phosphor layer. By increasing the density, the sensitivity of the panel can be significantly improved.

The phosphor layer formed by the conventional manufacturing method (coating method) is a layer consisting of a binder containing and supporting stimulable phosphor particles in a dispersed state, and the phosphor layer has a relatively low relative density (
60% or less). Since the packing density of the phosphor is low and the amount of phosphor contained in a given layer thickness is small, there is a limit to the improvement in sensitivity. Furthermore, even if the thickness of the phosphor layer is increased, the presence of a large number of bubbles in the phosphor layer tends to cause scattering of excitation light or stimulated emission light, making it difficult to achieve a significant improvement in sensitivity. or 1 has a negative effect on image quality.

In the present invention, the phosphor layer is formed by a manufacturing method (sintering method) consisting of a step of molding a phosphor layer forming material containing a stimulable phosphor into a sheet shape and a step of sintering it. A phosphor layer consisting essentially of phosphor and having a relative density of 70% or more can be obtained. The panel of the present invention containing such a phosphor layer exhibits extremely high sensitivity due to the high packing density of the phosphor. That is, according to the manufacturing method of the present invention, anything other than the stimulable phosphor (such as a binder) is not used in the step of forming the phosphor layer, or even if it is used, it is burned out in the sintering process. , a phosphor layer consisting only of phosphor is obtained. In addition, the phosphor layer is formed in a state in which the phosphor is sintered in the sintering process so that the entire phosphor layer is densely packed, resulting in a phosphor layer with an extremely high relative density. Therefore, when compared with a panel with the same layer thickness of the phosphor layer obtained by the conventional manufacturing method, 1. The phosphor layer of the panel obtained by the method of the present invention does not contain a binder, and air bubbles are reduced. , and phosphors are present in extremely large quantities. Therefore, the amount of stimulated luminescence of the entire phosphor layer increases. Furthermore, the amount of radiation absorbed by the entire phosphor layer increases, which also relatively increases the amount of stimulated luminescence, thereby increasing sensitivity.

Furthermore, in the panel of the present invention, the thickness of the phosphor layer can be made thinner than in the conventional panel when the sensitivity is the same, so that an image with high 1g sharpness can be obtained. Further, since radiation noise such as X-rays can be reduced by increasing the amount of radiation absorbed per phosphor layer, images with excellent graininess can be obtained.

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

The phosphor layer, which is a characteristic feature of the present invention, is made of sintered stimulable phosphor and has a relative density of 70% or more. .

Hereinafter, the term "margin stimulable phosphor" refers to a phosphor that exhibits stimulated luminescence when irradiated with radiation and then with excitation light as described above.
From a practical standpoint, it is desirable that the phosphor be a phosphor that exhibits stimulated luminescence in the wavelength range of 300 to 500 nm when excited by excitation light in the wavelength range of 400 to 900 nm. Examples of stimulable phosphors used in the radiation image storage panel of the present invention include SrS:Ce, Sm, and SrS:Eu, which are described in US Pat. No. 3,859,527.

Sm, Th02: Er, and La2O2S:Eu
, Sm, ZnS described in JP-A-55-12142
:Cu, Pb, Ba0-xAl2O3:Eu (Tatashi,
0.8≦X≦lO), and Ml0・xSi02:
A (However, Ml is Mg, Ca, Sr, Zn, Cd,
or Ba, where A is Ce, Tb, Eu, Tm, Pb
, Tl, Bil or Mn, and X is 0.5≦X≦
B
a1-X-F1Mgx, Cay
) F X :aEu” (X is C1 and Br
at least -, and X and y are O<x
+y≦0.6 and xy≠0, and a is 10-'≦
a≦5XIO-2), LnO described in JP-A-55-12144
X: xA (Tatashi, Ln is La, Y.

At least one of Gd and Lu, X is at least one of C1 and Br, A is Ce and Tb
and X is 0<x<O,
).

It is described in Japanese Patent Application Laid-Open No. 55-12145 (B
a I-x, M''X) FX: y
A (M2'' is at least one of Mg, Ca, Sr, Zn, and Cd, X is at least one of C1, Br, and I, A is Eu, Tb, Ce,
At least one of Tm, Dy, Pr, Ho, Nd, Yb, and Er, and X is 0≦X≦0.6.
y is 0≦y≦0.2).

M” described in Japanese Patent Application Laid-Open No. 55-160078
FX-xA:yLn [However, the M seal is Ba, Ca, Sr
, Mg, Zn, and at least one of Cd, A
are Be01Mg01CaO, SrO, BaO, ZnO,
A≦L20'J, Y201,L
a2O3, In2O3, 5i02. TiO2, ZrO2
, GeO2,5n02, Nb2O6, Ta20g, and ThO2, Ln is Eu, Tb
, Ce, Tm, Dy, Pr, Ho, Nd, Yb
, Er, Sm, and Gd, X is at least one of C1, Br, and I, and X and y are each 5 x 10-'≦X≦0.
．． 5° and o<y≦0.2].
3. -X,Mx)F2-aBaX2:yEu,zA
[where, Mff is at least one of beryllium, magnesium, calcium, strontium, zinc, and cadmium, X is at least one of chlorine, bromine, and iodine, and A is at least one of zirconium and scandium. Yes, a, x, y, and 2 are each 0.5≦a≦1.25, O≦X≦l, l
Phosphor represented by the composition formula O-@≦y≦2X10-' and O<z≦10-2], JP-A-57-23
Described in Publication No. 673 (Bay-,,M'',)
F2. aBa) (2: yEu, zB [Tatashi, M'' is beryllium, magnesium, calcium, strontium, zinc.

and at least one of cadmium, X is chlorine,
at least one of bromine and iodine, a,
x, y, and 2 are each 0.5≦a≦1.25. O
≦X≦1.10-'≦y≦2×10-' and 0<z
A phosphor represented by the composition formula of
, -1,M"1B)F2"aBaX2:yEu,zA[
Tatami and Mll are beryllium, magnesium, calcium, strontium, and zinc.

and at least one of cadmium, X is chlorine,
at least one of bromine, 3 and iodine, A is at least one of arsenic and silicon, a, X, y,
and 2 are o, s≦a≦1.25.0≦X≦1, respectively
．． 10-”≦y≦2×10-′, and O<z≦5xl
A phosphor expressed by the following formula: O-'.

MUl described in Japanese Patent Application Laid-Open No. 58-69281
oX:xCe [However, Mlll is P', Nd, Pm,
is at least one trivalent metal selected from the group consisting of Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Bi, and X is one or both of the six groups and Br; , X is 0<x<O,l]
A phosphor represented by the composition formula B described in JP-A No. 58-206678
a I-x M x /2 L x /2 F X:
y E u-' ” [M represents at least one alkali metal selected from the group consisting of Li, Na, Rb, and Cs; L represents Sc, Y, La.
,Ce,'Pr,N4. Pm, Sm, Gd, Tb', D
y, Ho.

Er, Tm, Yb, Lu, A sentence, Ga
, In, g, and Tl; X represents at least one halogen selected from the group consisting of In, Br, and I; and X It 10- 2≦X≦0.5, y
is a phosphor represented by the composition formula: o<y≦0.1] Ba described in JP-A No. 59-27980
FX-xA: yEu”

At least one halogen selected from the group consisting of C1, Br, and I; A is a fired product of a tetrafluoroboric acid compound; and X is 1o-6≦X≦o
, 1. y is o<y≦0.1] A phosphor represented by the composition formula: BaF described in JP-A No. 59-47289
X-xA: yEu'' [where X is at least one halogen selected from the group consisting of C1, Br, and I; It is a fired product of at least one compound selected from the group of hexafluoro compounds consisting of salts of valent or divalent metals; and X is 10-6≦X≦0.1, 3/ is o<y≦
0.1].

BaF described in Japanese Patent Application Laid-Open No. 59-56479
X-xNaX':aEtJ" [However, X and X
A phosphor represented by the composition formula: o is at least one of I, Br, and I, and X and a are O<x≦2 and Ova≦0.2, respectively; M”F described in Publication No. 59-56480
X−xNaX′:yEu”:zA [However, Ml is B
a, Sr, and Ca; X and Xo each contain at least one halogen selected from the group consisting of C1, Br, and ■; A is V, Cr, Mn
, Fe, Co, and Ni; and X is 0<x≦2, and y is o<
y≦0.2, and Z is O<z≦10-2], M'F described in JP-A-59-75200
X-aM'X'-bM'HX" 2 ・cM@
X'', '3 ・xA: yEu2° [However, M violet is at least one kind of alkaline earth metal selected from the group consisting of Ba, Sr, and Ca, M + is Li,
At least one alkali metal selected from the group consisting of Na, Rh, and Cs, and M'l is Be.
and Mg, Mff is at least one trivalent metal selected from the group consisting of Al, Ga, In, and Tl, and zA is a metal oxide. Items available: X is C9,, B'',
and at least one kind of halogen selected from the group consisting of I;
r, and at least one kind of halogen selected from the group consisting of I; and a is 0≦a≦2, and b is 0≦
b≦10-2. c is 0≦C≦10-2, and a + b
+ c≧1O-6: X is O<x≦0.5, y is o<y≦0.2''i (is), a phosphor represented by the composition formula, JP-A-60-84381 M”X listed in the official gazette
2-aM"X' 2: xEu" [T, Mll is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca: X and X" are C9
, Br, and at least one halogen selected from the group consisting of I, and x+x': and a
is 0.1≦a≦10.0, and X is O<x≦0.2. A stimulable phosphor is represented by the following composition formula:
FX-aM 'X': xEu2° [Tap,
Ml is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca; Ml is at least one alkali metal selected from the group consisting of Rb and Cs; is at least one kind of halogen selected from the group consisting of;
, C1, Br, and ■; and a and X are 0≦a≦4.0 and O<x≦0.2, respectively]. exhaustible phosphor, M'X:xBi [where Ml is at least one alkali metal selected from the group consisting of Rb and Cs; Yes: X is C love.

A stimulable phosphor containing at least one kind of halogen selected from the group consisting of Br and I'll come.

Furthermore, M′
The X E u "stimulable phosphor may contain the following additives in the following proportions per 21 moles of M'X2.aM"X".

bM described in JP-A-60-166379
'X' (However, Ml is at least one alkali metal selected from the group consisting of Rb and Cs, and
is at least one kind of halogen selected from the group consisting of F, C1, Br and ■, and b is o<b≦10
．． 0): bKX"-cMgX"'2-dMWX"" described in JP-A-60-221483,
(However, Mff[ is Sc, Y, La, Gd and Lu
is at least one trivalent metal selected from the group consisting of
and at least one kind of halogen selected from the group consisting of I, and s, c and d are each 0≦b
≦2.0. O≦C≦2゜0.0≦d≦2.0,
(2 x l O-'≦b+c+d); yB described in JP-A-60-228592 (where y is 2 x l O-'≦y≦2XIO-')
; b described in Japanese Patent Application Laid-Open No. 60-228593
A (A is at least one kind of oxide selected from the group consisting of 5i02 and p2o, and b satisfies 10-4≦b≦2×10-“): Japanese Patent Application No. 59 -2
bSin (b is o<b≦3xlO-2) described in specification No. 40452: Japanese Patent Application No. 1983-2
bSnX"2 (X" is at least one kind of halogen selected from the group consisting of F, CI, Br and I, and b is o
<b≦l0-3): bCsX″/cSnX″°2 described in Japanese Patent Application No. 1987-78033 (where X″ and Xl are each a group consisting of F, C1, Br, and ■) at least one kind of halogen selected from
and 10-6≦C≦2×10-2): and bCs described in Japanese Patent Application No. 60-78035
X”・y L n ” (X” is F, C1, Br
and I, and Ln is Sc, Y, Ce, Pr, Nd, Sm
, Gd, Tb, Dy, Ho, Er, Tm, Yb and L
at least one rare earth element selected from the group consisting of u, and b and y each satisfy o<b≦1O0
0 and IO ≦y≦1.8X 10-').

Among the above-mentioned photostimulable phosphors, divalent europium-activated alkaline earth metal halide phosphors are particularly preferred because they exhibit high-intensity stimulated luminescence. 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.

The white phosphor layer in step A below can be formed, for example, by the following manufacturing process.

That is, the manufacturing process of the phosphor layer consists of a step of molding a phosphor layer forming material containing a stimulable phosphor into a sheet shape, and a step of sintering this molded product.

In the process of molding the phosphor layer forming material into a sheet,
As the material for forming the phosphor layer, a powder consisting of particles of the above-mentioned stimulable phosphor can be used.

Moreover, a dispersion containing particles of the above-mentioned stimulable phosphor and a binder can also be used as the material for forming the phosphor layer. In this case, the stimulable phosphor and binder are added to a suitable solvent and then thoroughly mixed to prepare a dispersion in which phosphor particles are uniformly dispersed in the binder solution.

As the binder, it is preferable to use a substance that has suitable properties in terms of dispersibility of the phosphor or dispersion during the sintering process. Examples of this include paraffin (e.g., carbon number = 16 to 40, melting point: 37.8 to 64.5°C); wax (natural waxes include: candelilla wax, carnauba wax, rice wax, Vegetable waxes such as wood wax, animal waxes such as beeswax, lanolin, spermaceti, mineral waxes such as montan wax, osikelite, and ceresin, and synthetic waxes such as polyethylene wax and coal-based synthetic waxes such as Fischer-Tropsch wax. , hydrogenated castor oil, fatty acid amide, ketone, and other oil-based synthetic waxes) Niresin (polyvinyl butyral, polyvinyl acetate, nitrocellulose, ethylcellulose, vinylidene chloride/vinyl chloride copolymer, polyalkyl (meth)acrylate,
(vinyl chloride/vinyl acetate copolymer, polyurethane cellulose acetate butyrate, polyvinyl alcohol, linear polyester), etc. Proteins such as gelatin, polysaccharides such as dextran, or gum arabic can also be used.

Examples of solvents include lower alcohols such as methanol, ethanol, n-propertool, and n-butanol; chlorine-containing hydrocarbons such as methylene chloride and ethylene chloride; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; methyl acetate; Esters of lower fatty acids and lower alcohols such as ethyl acetate and butyl acetate; ethers such as dioxane, ethylene glycol monoethyl ether, and ethylene glycol monomethyl ether; and mixtures thereof.

The mixing ratio of the binder and the stimulable phosphor in the above dispersion varies depending on the type of phosphor and the molding conditions and sintering conditions described below, but in general, the mixing ratio of the binder and the stimulable phosphor is l :l to 1:100 (weight ratio), and particularly preferably from l:8 to 1:40 (weight ratio).

Note that the dispersion liquid may contain additives such as a dispersant for improving the dispersibility of the phosphor. Examples of dispersants used for such purposes include phthalic acid, stearic acid, caproic acid, lipophilic surfactants, and the like.

- The powdered material made of phosphor particles prepared as described above or the dispersion containing phosphor particles and a binder is then molded into a sheet shape.

When the material for forming the phosphor layer is a powder, it is preferable to mold the material into a sheet by pushing the powder into a mold. The mold used for molding is usually a rectangular mold. In addition, if the phosphor layer forming material is a dispersion liquid, it can be coated onto a suitable substrate (support or another sheet) using a normal coating method (for example, using a doctor blade) and formed into a sheet. Alternatively, it is preferable to mold it into a sheet by placing it in a mold in the same way as the powdered material described above.

In the above molding process, compression treatment may be performed.
Sometimes, when the material for forming the phosphor layer is a powder, compression treatment is performed. The compression treatment is carried out, for example, by press molding, and is preferably carried out by applying a pressure in the range of 1xlO2 to Lx10'kg/cm''.This makes it possible to further increase the relative density of the resulting phosphor layer.

Next, the sheet-shaped molded product obtained as described above is sintered.

Sintering is performed, for example, in a firing furnace such as an electric furnace. The sintering temperature and sintering time vary depending on the type of phosphor layer forming material, the shape and condition of the sheet-like molded product, and the type of stimulable phosphor used therein.

In the case of a sheet-like molded product or a powdered product made of a stimulable phosphor, the sintering temperature is generally in the range of 500 to 1000°C, preferably in the range of 700 to 950°C. Further, the sintering time is generally in the range of 0.5 to 6 hours, preferably in the range of 1.5 to 2 hours. The sintering atmosphere is usually a neutral gas atmosphere such as a nitrogen gas atmosphere or an argon gas atmosphere, or a weakly reducing atmosphere such as a nitrogen gas atmosphere containing a small amount of hydrogen gas, or a carbon dioxide atmosphere containing -carbon oxide. do.

In addition, in the case of a sheet-shaped molded product or a dispersion containing a stimulable phosphor and a bond, the binder in the sheet-shaped molded product must be heated in advance in a neutral gas atmosphere such as a nitrogen gas atmosphere, an argon gas atmosphere, or an oxygen gas atmosphere. It is preferable to diffuse the material under an oxidizing gas atmosphere such as a gas atmosphere or air atmosphere at a relatively low temperature (temperature in the range of 100 to 400° C.), and then sinter it under the above-mentioned sintering conditions. Due to the nature of the binder in this low temperature range, components other than the binder and the stimulable phosphor are
It volatilizes or carbonizes at around 400°C and becomes carbon dioxide gas, which can be easily removed.

As a result, the resulting phosphor layer is composed only of phosphors. Preferably, the time for cold aeration is in the range of 0.5 to 6 hours. In this way, the phosphor layer is formed with a relative density of 70% or more. In this case, the grain boundary size of the phosphor is preferably in the range of 1 to 1100 JL.

Note that the compression treatment may be performed before the sintering process as described above, or may be performed during the sintering process. That is,
Sintering may be performed while performing compression treatment. This is particularly suitable when the sheet-like molded product is a powdered material consisting only of phosphor particles.

The thickness of the phosphor layer formed in this manner varies depending on the characteristics of the intended radiation image conversion panel, but is usually 20 lm to 1 mm.

However, the thickness of this layer is preferably 50 to 500 gm, particularly preferably 250 to 300 gm.

The relative density of the phosphor layer formed by the above method is
It can be calculated theoretically using the following equation (I).

Vp/V=aA/ (a+b)p XV---(I)
- (Top, V: Total volume of the phosphor layer vp: Volume of the phosphor A: Total weight of the phosphor layer px: Density of the phosphor a: Weight of the phosphor b = Weight of the binder) This invention Here, the relative density of the phosphor layer is a value calculated using equation (I). However, in the phosphor layer formed by sintering, the binder is burned out, so b
is ~0.

Next, a support is provided on one surface of the formed phosphor layer.

The support used in the present invention can be arbitrarily selected from various materials used as supports for intensifying screens in conventional radiography methods or materials known as supports for radiation image conversion panels. . Examples of such materials include cellulose acetate, polyester,
Pigment paper containing pigments, such as films of plastic materials such as polyethylene terephthalate, polyamide, polyimide, triacetate, polycarbonate, metal sheets such as aluminum foil, aluminum alloy foil, ordinary paper, baryta paper, resin coated paper, titanium dioxide, etc. Examples include paper sized with polyvinyl alcohol or the like. 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 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 high sharpness type radiation image conversion panel, and the latter is a support suitable for a high sensitivity type radiation image conversion panel.

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

Furthermore, as described in JP-A No. 58-200200, in order to improve the sharpness of images, adhesives are added to the surface of the support on the phosphor layer side (the surface of the support on the phosphor layer side). When an imparting layer, a light reflecting layer, a light absorbing layer, etc. are provided, fine irregularities may be uniformly formed on the surface (meaning the surface thereof).

Usually, the support is attached to the phosphor layer by applying a commonly used adhesive on one side of the support and pressing one side of the phosphor layer onto that surface. Note that when a sheet-like molded product is provided on a substrate by coating, this is done after separating the phosphor layer from the substrate.

Alternatively, the support can be provided at the same time by placing the sheet-like molded product obtained in the molding process on the support and performing the sintering process. In the case of coating, a support may be used in advance as a substrate.

When the support is attached at the same time as the phosphor layer is formed in the sintering process, preferred materials for the support include, for example, quartz, zirconia, and alumina.

Examples include sheets made of inorganic materials such as silicon carbide.

It is preferable that a transparent protective layer is provided on the surface of the phosphor layer opposite to the side in contact with the support for the purpose of physically and chemically protecting the phosphor layer.

The transparent protective film may be made of, for example, 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 phosphor layer with a solution prepared by dissolving a transparent polymer material such as polyethylene terephthalate in an appropriate solvent.
A plastic sheet made of polyethylene, polyvinylidene chloride, polyamide, etc.: A protective film-forming sheet such as S or a transparent glass plate is separately formed and bonded to the surface of the phosphor layer using an appropriate adhesive. can also be formed. The thickness of the transparent protective film thus formed is preferably about 3 to 20 gm.

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

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

[Example 1] Powdered divalent europium activated barium fluoride bromide phosphor particles (B a F B r,: 0.001 E u ”
) was pressed into a mold and compressed into a sheet.

Compression is done using a press molding machine (pressure crab 10'kg/crrr'
, temperature = 25°C).

Next, this was placed in a high-temperature electric furnace and sintered. Sintering was carried out at a temperature of 750° C. in a nitrogen gas atmosphere for 1.5 hours. After sintering, the sintered product was taken out of the electric furnace and cooled to form a phosphor layer consisting only of phosphor with a layer thickness of 250 gm.

Carbon black kneaded polyethylene terephthalate sheet (support, thickness = 25
A support was attached by adhering to the base (0 lm) using a polyester adhesive.

Furthermore, on the other side of the phosphor layer (the side opposite to the support), a transparent film of polyethylene terephthalate (thickness: 12 gm, coated with a polyester adhesive) was placed with the adhesive layer side facing down. By placing and adhering, a transparent protective film was formed.

In this way, a radiation image storage panel composed of a support, a phosphor layer, and a transparent protective film was manufactured.

[Example 21 to [Example 61] In Example 1, the molding conditions and sintering conditions were changed to the following
By performing the same operations as in Example 1 except for changing the molding pressure and sintering temperature as shown in the table, various radiographic images composed of a support, a phosphor layer, and a transparent protective film were prepared. A conversion panel was manufactured.

Table 1 Pressure (kg/am') Sintering temperature (℃) Example 2
10' 850 Example 3 10 pieces 950 Example 4 3xlO' 75
0 Example 5 3xlO3850 Example 6 3xlO' 950 [Example 7] Powdered divalent europium activated barium fluoride bromide phosphor particles (B a F B r : 0.01 E u 2°
) and an acrylic resin to prepare a dispersion containing phosphor particles in a dispersed state. Next, this dispersion liquid is sufficiently stirred and mixed using a propeller mixer to ensure that the phosphor particles are uniformly dispersed and the mixing ratio of the binder and the phosphor particles is 1:20. A coating solution having a viscosity of 35 to 50 PS (25°C) was prepared.

Next, the obtained coating solution was uniformly applied onto a horizontally placed Teflon sheet using a doctor blade. After coating, the Teflon sheet on which the coating film had been 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. After drying, the coating film was peeled off from the Teflon sheet, placed on a quartz plate, and placed in a high-temperature electric furnace to diffuse the binder and further sinter. Initial binder aeration was carried out at a temperature of 400 °C in an air atmosphere for 4 hours, and then sintering was carried out at a temperature of 85 °C in a nitrogen gas atmosphere.
The test was carried out at a temperature of 0°C for 2 hours.

The obtained sintered product was taken out of the electric furnace and cooled to form a phosphor layer consisting only of phosphor with a layer thickness of 250 gm.

Carbon black kneaded polyethylene terephthalate sheet (support, thickness: 25
07tm) using a polyester adhesive to attach a support.

Furthermore, on the other side of the phosphor layer (the side opposite to the support), a transparent film of polyethylene terephthalate (thickness: 124 m, coated with a polyester adhesive) was placed with the adhesive layer side facing down. By placing and adhering, a transparent protective film was formed.

In this way, a radiation image storage panel was produced, which consisted of a support, a phosphor layer, and a transparent protective W1 film.

[Example 8] In Example 7, instead of applying the coating solution onto a horizontally placed Teflon sheet using a doctor blade, a stainless steel mold was placed on the Teflon sheet, and the dispersion was poured into this mold and applied onto the sheet. A radiation image storage panel composed of a support, a phosphor layer and a transparent protective film was manufactured by performing the same operations as in Example 7, except for molding into a transparent protective film.

[Comparative Example 1] Methyl ethyl ketone was added to a mixture of powdered divalent europium-activated barium fluoride bromide phosphor particles (BaFBr: 0.001Eu") and a linear polyester resin, and a mixture with a nitrification degree of 11.5% was added. A dispersion containing phosphor particles in a dispersed state was prepared by adding nitrocellulose.Next, tricresyl phosphate, n-butanol, and methyl ethyl ketone were added to this dispersion, followed by thorough stirring using a propeller mixer. When mixed, the phosphor particles are uniformly dispersed and the mixing ratio of the binder and the phosphor particles is 1:20.
A coating liquid having a viscosity of 25 to 35 PS (25°C) was prepared.

Next, the obtained coating solution was uniformly applied using a doctor blade onto a carbon black-mixed polyethylene terephthalate sheet (support, thickness: 250 JLm) placed horizontally on a glass plate. After coating, the glass plate 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.
The coating film was dried. In this way, a sheet was obtained having a support and a phosphor layer of approximately 250 pm in layer H provided on the support.

Then, a transparent film of polyethylene terephthalate (thickness: 121 Lm, coated with a polyester adhesive) was placed on top of the phosphor layer of the sheet with the adhesive layer side facing down and adhered. A protective film was formed.

In this way, a radiation image storage panel composed of a support, a phosphor layer, and a transparent protective film was manufactured.

[Comparative Example 2] Methyl ethyl ketone was added to a mixture of powdered divalent europium-activated barium fluoride bromide phosphor particles (BaFBr: 0.001Eu") and a linear polyester resin, and a mixture with a nitrification degree of 11.5% was added. A dispersion containing phosphor particles in a dispersed state was prepared by adding nitrocellulose.Next, tricresyl phosphate, n-butanol, and methyl ethyl ketone were added to this dispersion, followed by thorough stirring using a propeller mixer. Mix to ensure that the phosphor particles are uniformly dispersed and the mixing ratio of the binder and the phosphor particles is 1:2.
A coating liquid having a viscosity of 25 to 35 Ps (25° C.) was prepared.

Next, the obtained coating solution was uniformly applied using a doctor blade onto a carbon black-mixed polyethylene terephthalate sheet (support, thickness: 250 pm) placed horizontally on a glass plate. After coating, the glass plate 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 to dry the coating film, and then it is placed on the support. A sheet having a phosphor layer was obtained.

Next, the above sheet was molded using a press molding machine (pressure = 10 kg).
/crf, temperature = 25°C). In this way, a phosphor layer having a layer thickness of about 2501 Lm was obtained on the support.

Then, a transparent film of polyethylene terephthalate (thickness: 12 μm, coated with a polyester adhesive) is placed on top of the compressed phosphor layer with the adhesive layer side facing down, and then bonded. , a transparent protective film was formed.

In this way, a radiation image storage panel composed of a support, a phosphor layer, and a transparent protective film was manufactured.

[Comparative Example 3] to [Comparative Example 4] In Comparative Example 2, a support was prepared by performing the same operation as in Comparative Example 2, except that the compression treatment was performed at a pressure as shown in Table 2 below. , various radiation image storage panels constructed from a phosphor layer and a transparent protective film were manufactured.

Table 2 Pressure (kg/cm'') Comparative Example 3 10' Comparative Example 4 3xlO? In this case, the density of the phosphor and the density of the binder were 5.18 g/crrI' and 1.15 g/crn, respectively.
'There was.

Next, each radiation image conversion panel was evaluated by performing the following sensitivity test.

After irradiating the radiation image conversion panel with X-rays at a tube voltage of 80 Vp, a He-Ne laser beam (wavelength: 633 m) was applied to the radiation image conversion panel.
The sensitivity was measured by excitation.

The results obtained are summarized in Table 3.

All days below Table 3 Relative density (%) Relative sensitivity example 1 75 104 Same 2 80 1f 0 Same
3 85. 141 same 4
85 126 same 5
88 148 same 6
88 14B same 7
93 175 same 8
90 170 Comparative example 1 50
to.

2 60 96
3 70 89
4 80 74
As is clear from the results shown in Table 3, the radiation image conversion panels (Examples 1 to 3) obtained by the sintering method of the present invention
8) had significantly improved sensitivity compared to the radiation image conversion panel (Comparative Example 1) obtained by the conventional coating method. On the other hand, the radiation image conversion panels obtained by the known compression method (Comparative Examples 2 to 4) had lower sensitivity than the radiation & 1 image conversion panel (Comparative Example 1) obtained by the coating method.

Patent Applicant Fuji Photo Film Co., Ltd. Agent Patent Attorney Yasushi Yanagawa Otokozo F Tsunen City Shosha December 2, 1986 ゛・、・＼

Claims (1)

[Scope of Claims] 1. A radiation image conversion panel having a support and a phosphor layer made of a stimulable phosphor provided thereon, in which the phosphor layer is sintered. A radiation image conversion panel comprising a phosphor and having a relative density of the phosphor layer of 70% or more. 2. The grain boundary size of the stimulable phosphor is 1 to 100 μm
The radiation image conversion panel according to claim 1, wherein the radiation image conversion panel is within the range of . 3. The radiation image conversion panel according to claim 1, wherein the stimulable phosphor is a divalent europium activated alkaline earth metal halide phosphor. 4. In a method for manufacturing a radiation image conversion panel having a support and a phosphor layer made of a stimulable phosphor provided thereon, a phosphor layer forming material containing a stimulable phosphor is formed into a sheet. 1. A method for producing a radiation image storage panel, which comprises forming a phosphor layer by molding and then sintering the molded product. 5. Claim 4, characterized in that the material for forming the phosphor layer is a powdered material made of a stimulable phosphor, and the powdered material is molded into a sheet by pushing it into a mold. A method of manufacturing the radiation image storage panel described above. 6. The material for forming the phosphor layer is a dispersion containing a stimulable phosphor dispersed in a binder solution, and the dispersion is molded into a sheet by pouring it into a mold. A method for manufacturing a radiation image conversion panel according to claim 4. 7. The material for forming the phosphor layer is a dispersion containing a stimulable phosphor dispersed in a binder solution, and the dispersion is formed into a sheet by applying the dispersion onto a substrate. A method for manufacturing a radiation image conversion panel according to claim 4. 8. Sintering of the molded product made of the above powder in a neutral gas or reducing gas atmosphere and at a sintering temperature of 500 to 1
The method for manufacturing a radiation image conversion panel according to claim 5, characterized in that the manufacturing method is carried out at a temperature of 0.000°C. 9. Sinter the molded product made of the above powder in a neutral gas or reducing gas atmosphere and at a sintering temperature of 700 to 9
A method for manufacturing a radiation image conversion panel according to claim 8, characterized in that the manufacturing method is carried out at a temperature of 50°C. 10. Diffusion of the binder in the molded product made of the above dispersion,
In a neutral gas or oxidizing gas atmosphere and at a temperature of 10
After the sintering is performed at a temperature in the range of 0 to 400°C, sintering is performed in a neutral gas or reducing gas atmosphere and at a sintering temperature in the range of 500 to 1000°C. 8. A method for producing a radiation image conversion panel according to item 7. 11. Diffusion of the binder in the molded product made from the above dispersion in a neutral gas or oxidizing gas atmosphere at a temperature of 3.
00 to 400 °C, and then sintering is carried out in a neutral gas or reducing gas atmosphere at a sintering temperature of 700 to 950 °C. A method for manufacturing a radiation image conversion panel. 12. The method for producing a radiation image storage panel according to claim 4, wherein the stimulable phosphor is a divalent europium activated alkaline earth metal halide phosphor.