JPS62137598A - Radiation picture conversion panel - Google Patents

Abstract

(57) [Summary] 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. More particularly, the present invention relates to a radiation image converting channel having a light reflecting layer between a support and a phosphor layer.

[Technical Background of the Invention and Prior Art] To obtain a radiation image as an image, a combination of a radiographic film having an emulsion layer made of a silver salt photosensitive material and an intensifying screen has been used. G1 so-called radiography is used. Recently, a radiation image conversion method using a stimulable phosphor, as described in Japanese Patent Application Laid-Open No. 55-12145, has been attracting attention as an alternative method to the above-mentioned radiographic method. became. This radiation image conversion method utilizes a radiation image conversion panel (stimulable phosphor sheet) containing a stimulable phosphor.

The radiation transmitted through the subject or the radiation emitted from the subject is absorbed by the stimulable phosphor of the panel, and then the stimulable phosphor is exposed to electromagnetic waves (excitation light) such as visible light and infrared rays in a time series. By exciting the stimulable phosphor, the radiation energy stored in the stimulable phosphor is released as fluorescence (stimulated luminescence), and this fluorescence is read photoelectrically to obtain an electrical signal. It is used to create images.

This radiographic image conversion method has the advantage that it is possible to obtain a wealth of radiological images with a much lower exposure dose than when using conventional radiographic methods. Therefore, this radiation image conversion method has a very high utility value especially in direct medical radiography such as X-ray photography for the purpose of medical diagnosis.

The basic structure of the radiation image conversion panel used in the radiation image conversion method is a support and a phosphor layer provided on one side of the support. Note that a transparent protective film is generally provided on the surface of the phosphor layer opposite to the support (the surface not facing the support) to protect the phosphor layer from chemical deterioration or Protects from physical impact.

The phosphor layer consists of a stimulable phosphor and a binder that contains and supports the stimulable phosphor in a dispersed state. After absorbing radiation such as It has the property of emitting light (stimulated luminescence) when irradiated with electromagnetic waves (excitation light) such as. 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. It is formed as an image of accumulated energy. This M accumulation can be emitted as stimulated luminescence by being excited in time series with the electromagnetic waves mentioned above, and by photoelectrically reading this stimulated luminescence and converting it into an electrical signal, an image of accumulated radiation energy can be obtained. It becomes possible to create an image.

The radiation image conversion method is a very advantageous image forming method as mentioned above, but the radiation image conversion panel used in this method is also highly sensitive, similar to the intensifying screen used in conventional radiography. It is desired that the image quality (g sharpness 2 graininess, etc.) is high and provides an image with good image quality. In particular, when the subject is a human body, it is desired that the sensitivity of the panel be as high as possible in order to reduce the exposure dose as much as possible.

Conventionally, techniques for improving the sensitivity of radiation image conversion panels include vapor-depositing metals such as aluminum on the surface of the support, laminating metal foils such as aluminum foil, etc.
Alternatively, it is known that a light reflective layer is provided on the support by coating a coating liquid containing a white pigment (light reflective substance) dispersed in a suitable binder, and a phosphor layer is provided on top of the light reflective layer. ing. As white pigments, titanium dioxide, white lead, zinc sulfide, aluminum oxide, bugnesium oxide, alkaline earth metal fluorohalides, etc. are used (Japanese Patent Laid-Open No. 56-12600 and Japanese Patent Application No. 58-3).
No. 7838), whereby the light emitted from the stimulable phosphor in the phosphor layer and directed towards the support is reflected without being absorbed by or transmitted through the support. The light is reflected by the layer and emitted from the surface of the panel on the phosphor layer side, and therefore, this reflected light is also detected by the photoelectric conversion device and converted into an electrical signal.

[Summary of the Invention] An object of the present invention is to provide a radiation image conversion channel with improved sensitivity.

Another object of the present invention is to provide a radiation image conversion panel with improved sensitivity and graininess without substantially reducing image sharpness.

The purpose of Section L is to form a support, a light-reflecting layer consisting of a binder containing and supporting a light-reflecting substance in a dispersed state, and a phosphor layer consisting of a binder containing and supporting a stimulable phosphor in a dispersed state. This can be achieved by the radiation image storage panel of the present invention, in which the light reflecting layer contains polymer particles having a hollow structure as a light reflecting material.

That is, the present invention uses hollow-structured particles made of a polymer material instead of a conventional white pigment as a light-reflecting material used in the light-reflecting layer of a radiation image storage panel, thereby significantly improving the sensitivity of the panel. This will result in significant improvements.

As a result of repeated research in order to prevent the stimulated luminescence light from the stimulable phosphor from scattering toward the support and disappearing, the present inventor created a large number of microscopic voids in a layer made of a polymeric material. The researchers discovered that the light reflection properties of the layer can be enhanced by taking advantage of the large difference in refractive index between the polymer material and air, and the formation of these minute voids can be reduced by forming hollow structured polymer particles. This invention was specifically achieved by dispersing it in the binder layer.

According to the present invention, the stimulated luminescent light directed toward the support is
In the light reflecting layer, the light is reflected at the interface due to the difference in refractive index between the polymer shell of the hollow particle and the air inside, and is emitted from the phosphor layer side surface of the panel (readout side of the panel) and detected as image information. be done.

Until now, almost no particles of polymeric substances with hollow structures were known, and in particular, it was impossible to obtain fine particles with an outer diameter of 1 μm or less, but very recently, such particles have been discovered. 9 In the radiation image storage panel of the present invention in which hollow polymer particles (polymer pigments) have been developed, a coating solution containing these hollow polymer particles dispersed in a suitable binder is coated on a support, or By adhering a separately formed thin film in which hollow polymer particles are dispersed using an adhesive, a binder layer having a large number of minute voids can be provided as a light reflecting layer.

Accordingly, the sensitivity of the radiation image conversion panel can be increased. In particular, the hollow polymer particles used in the present invention have excellent reflective properties even in the short wavelength region of 300 to 450 nm, compared to white pigments such as titanium dioxide conventionally used in light reflective layers. For this reason,
As a stimulable phosphor for the panel, near-ultraviolet and +i (which exhibits stimulated luminescence in the viewing region) such as divalent europium-activated alkaline earth total fluoride halide phosphor (emission peak wavelength: approximately 390 nm) can be used. When using phosphors, the sensitivity of the panel can be significantly increased.

Furthermore, compared to white pigments such as alkaline earth metal fluorohalides whose reflection spectra extend into the short wavelength region, the hollow polymer particles used in the present invention can be made into fine particles by appropriately selecting a binder. Even if it is present, the dispersibility does not deteriorate, and since it is relatively inexpensive, the manufacturing cost of the panel can be reduced.

Furthermore, since readout of a radiation image conversion panel is usually performed by irradiating excitation light in a time-series manner (scanning the panel with excitation light), the sharpness of the obtained image depends on the spread of stimulated luminescence light in the panel. rather, it is affected by the spread of the excitation light. In conventional radiation image conversion panels equipped with a light reflection layer, the excitation light that has passed through the phosphor layer is also reflected by the light reflection layer, which spreads out in the phosphor layer, resulting in an increase in sharpness. There was a tendency for images with a slightly lower quality to be obtained. However, according to the radiation image conversion panel of the present invention, the sensitivity can be significantly increased wJ without substantially reducing the sharpness of the image.

Furthermore, it is possible to significantly improve image graininess while improving sensitivity. In other words, if the image quality such as sensitivity and graininess is equivalent to that of conventional radiation image conversion panels, the thickness of the phosphor layer can be made thinner, and as a result, the sharpness can be increased. It is something that can be done.

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

The support used in the present invention can be arbitrarily selected from various materials used as supports for intensifying screens in conventional radiography methods or materials known as supports for radiation image conversion panels. . Examples of such materials include cellulose acetate, polyester,
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, pigment paper containing pigments such as titanium dioxide, 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.

The surface of the support is coated with a polymeric substance such as gelatin in order to strengthen the bond with the light-reflecting layer provided on it.
Alternatively, an antistatic layer made of a conductive material such as In203.5n02 may be provided for the purpose of improving the antistatic performance of the panel.

Next, a light reflective layer is provided on the support.

The light-reflecting layer, which is a characteristic feature of the present invention, is a layer made of a binder containing and supporting polymer particles having a hollow structure in a dispersed state as a light-reflecting substance.

The hollow structured polymer particles (polymer pigments) used in the present invention generally have an outer diameter in the range of 0.2 to 1 μm, and a small pore diameter (inner diameter) of 0.05 to 0.7 μm.
These are fine particles in the range of m. Specific examples of hollow polymer particles include styrene polymer particles obtained by adding a suitable crosslinking agent to styrene and/or acrylic monomers and bonding them into a spherical shell (core-shell polymerization); Mention may be made of acrylic copolymer particles.

Since these hollow polymer particles have voids inside, light passing through the polymer pores is diffusely reflected by the walls of the voids, and therefore has a white luster similar to that of inorganic pigments such as titanium dioxide. In addition, the reflection spectrum of hollow polymer particles ranges from the near-ultraviolet region to the visible region (long wavelength region of 300 nm or more), and in particular in the near-ultraviolet region of 300 to 450 nm, it has traditionally been used in light reflective layers. The hollow polymer particles exhibit a high reflectance that cannot be obtained with white pigments such as titanium dioxide, which is known as a light-reflecting substance.Therefore, the hollow polymer particles contain a stimulable phosphor that exhibits stimulated luminescence in the near-ultraviolet and visible regions. It is particularly suitable as a light-reflecting material for radiation image conversion panels.

The light-reflecting layer is prepared by adding the hollow polymer particles described above to a suitable binder and mixing thoroughly to prepare a coating solution in which the hollow polymer particles are uniformly dispersed in the binder. After forming a coating film of the coating liquid by applying the coating solution to the substrate, the coating film can be formed on the support by heating and drying the coating film. Or, separately, glass plate, metal plate,
A light-reflecting layer can also be provided by applying a coating solution onto a sheet such as a plastic sheet and drying it to form a thin film containing dispersed hollow polymer particles, and then bonding this to a support using an adhesive. good.

The binder for the light-reflecting layer can be selected from water-based polymeric substances such as acrylic acid ester copolymers, as well as those used as binders for the phosphor layer, which will be described later.

The mixing ratio of the binder and the hollow polymer particles in the coating solution is generally selected from the range of 1=1 to 1:50 (weight ratio), and preferably 1:2 to 1 from the viewpoint of adhesion to the support. :20 (weight ratio). Note that a known light-reflecting substance such as a white pigment may be added to the coating liquid, and the light-reflecting layer formed may be made of a mixture of hollow polymer particles and a white pigment, for example,
When mixed with titanium dioxide, the hollow polymer particles can fill the voids of the larger particle size titanium dioxide, increasing the shielding power compared to conventional titanium dioxide alone. Further, the thickness of the light-reflecting layer is preferably in the range of 5 to 100 lumens.

Furthermore, for the purpose of improving sharpness as described in Japanese Patent Application Laid-Open No. 58-200200.

Fine irregularities may be provided on the surface of the light reflecting layer.

Next, a phosphor layer is formed on the light reflective layer.

The phosphor layer is basically a layer consisting of a binder containing and supporting particles of stimulable phosphor in a dispersed state.

As mentioned above, a stimulable phosphor is a stimulable phosphor that exhibits stimulated luminescence when it is irradiated with radiation and then irradiated with excitation light, but from a practical point of view it is a stimulable phosphor with a wavelength in the range of 400 to 900 nm. It is desirable that the stimulable phosphor is a stimulable phosphor that exhibits stimulated luminescence in the wavelength range of 300 to 500 nm using excitation light at
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, BaO*xAuzOz :Eu (however, 0.8≦X≦10), and M''O・xS
i O2: A (However, M is Mg, Ca, Sr,
Zn, Cd, or Ha, and A is Ce, Tb, Eu
, Tm, Pb, Tl, Bi, or Mn, and X is
0.5≦X≦2.5).

It is described in Japanese Patent Application Laid-Open No. 55-12143 (B
a r−x −y * M g x , Ca y
) F X :aEu” (X is ci and Br
cl), and X and y are 0
x+y≦0.6, and xyso-t', a is 1
O-6≦a≦5X10-2), LnO described in JP-A-55-12144
X: xA (Ln is La, Y, Gd, and Lu
At least one of them, X is C! ; at least one of L and Br, A is at least one of Ce and Tb, and X is O<x<0.1), as described in JP-A-55-12145. (Ba
,-)1. M2°x) F Eu, Tb, Ce, Tm, Dy
, Pr, H0. At least one of Nd, Yb, and Er, where X is O≦X≦0.6, and y is O≦y
≦0.2), M”FX* xA : yLn [However, Ml is Ba, Ca, Sr, Mg, Zn
, and at least one of Cd(7), A is Bed
, MgO, CaO, 5rO1Bad, ZnO1A, O
,,Y2O1,La,0. , In2O3,5i02,T
lO2, ZrO2, GeO□, 5n02, Nb2o5,
Ta206, and at least one of ThO (7), Ln is): u, Tb, Ce, Tm, Dy, Pr,
H0. Nd, Yb, Er, Sm, and Gd
X is at least one of C1, Br, and I, and X and y are each 5
A stimulable phosphor represented by the composition formula:
a+-x 1M”X) F 2 ・a13 aX2
:yEu, zA [where Ml is at least one of beryllium, manesium, calcium, strontium, ][, and cacdomyla, X is at least one of chlorine, bromine, and iodine, and A is at least one of zirconium and scandium. At least one type, a,
x, y, and 2 are each 0.5≦a≦1.25.0
≦X≦1, to-"≦y≦2X10-', and 0<z
≦1O-2] is described in Japanese Patent Application Laid-Open No. 57-23673 (B
a,-,,M'z)F2''aBaX2:yE
u, zB [However, Ml is beryllium, magnesium,
at least one of calcium, strontium, zinc, and cadmium, X is at least one of chlorine, bromine, and iodine, and a, x, y, and 2
are respectively 0.5≦a≦1.25.0≦X≦1.10-
11≦y≦2×10−′, and 0<z≦2×10−′
A stimulable phosphor represented by the composition formula:

Described in Japanese Patent Application Laid-Open No. 57-23675
(B at-x, M"x) F2
No. aBaX 2 :yEu, zA [however
Ml 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 arsenic and silicon, and a, x , y, and 2 each satisfy 0.5≦a≦1.
25.0 ≦ M”O described in Publication No. 69281
X: xCe [However, M is Pr, Nd, Pm, Sm,
Eu, Tb, Dy, H0. Er, Tm, Yb, and B
at least one trivalent metal selected from the group consisting of i, X is one or both of C1 and Br, and X is 0<x<0.1] stimulable phosphor.

B described in Japanese Patent Application Laid-Open No. 58-206678
a l+ 71 M 11.2 L X /2 F X
: , E u ” [where M represents at least one type of alkaline compound selected from the group consisting of Li, Na, Rb, and Cs; L represents Sc, Y, La,
Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, H
o.

Er, Tm, Yb, Lu, Ajl Ga, I
n, and at least one trivalent metal selected from the group consisting of Tl; X represents at least one halogen selected from the group consisting of C, Br, and ■, and X represents to-'≦ X≦0.5, y≦
A stimulable phosphor represented by the composition formula:
X*xA: yEu” [However, X is.

C is at least one kind of halogen selected from the group consisting of Br, and ■; A is a fired product of a tetrafluoroboric acid compound; and
．． 1, y is o<y≦0.1].

BaF described in JP-A No. 59-47289
X* xA: yEu” [However, or C1, B
r, and at least one halogen selected from the group consisting of; A is a hexafluoro compound consisting of a monovalent or trivalent metal salt of hexafluorosilicic acid, hexafluorotitanic acid, hexafluorozirconic acid is a fired product of at least one compound selected from the group; and X is 1O-8≦X≦0.1, and y is O<
y≦0.1] A stimulable phosphor represented by the composition formula: BaF described in JP-A-59-56479
X* xNaX”: aEu2° [where X and X′
are each at least one of C1, Br, and engineering, and X and a are each O<X≦2. and O<a≦0.2], a photostimulable phosphor represented by the composition formula:
FX * x N aX':yEu'':zA[
However, MI[ is at least one kind of alkaline earth metal selected from the group consisting of Ba, Sr, and Ca; X and X'' are each at least one kind selected from the group consisting of C1, Br, and Has halogen;
A is V, Cr, Mn, Fe, G0. and at least one transition metal selected from Ni; and X is 0<X≦2, y is o<y≦0.2, and 2 is 0<2≦
A stimulable phosphor represented by the composition formula: 1O-2.

It is described in Japanese Patent Application Laid-open No. 59-75200 and 17N le M'F
'厘x″2・CM'X", 6 XA: yE u"
[However, MM is at least one alkaline earth metal selected from the group consisting of Ba, Sr, and Ca,
M + is at least one alkali metal selected from the group consisting of Li, Na, Rh, and Cs;
MI is at least one divalent metal selected from the group consisting of Be and Mg; MI is at least one trivalent metal selected from the group consisting of An, Ga, In, and Tl; A is a metal oxide and; X is 0 sentences, Br,
and ■ at least one kind of halogen selected from the group consisting of;
Br, and at least one kind of halogen selected from the group consisting of ■; and a is O≦a≦2, and b is 0≦
b≦10-2, C is O≦C≦10-2, and a+b+c
≧10-”c exists; X is O<X≦0.5, y is o<y≦
A stimulable phosphor represented by the composition formula of
2* aM"X' 2: xEu" [However, Ml
is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca;
2, at least one halogen selected from the group consisting of Br and I, and X≠X°; and a
is 0.1≦a≦10.0. x is O<X≦0.2]
A stimulable phosphor represented by the composition formula, tL tail M ” FX @ aM ′
xEu" [where MI is at least one kind of alkaline earth metal selected from the group consisting of Ba, Sr and Ca; MI is at least one kind of alkali metal selected from the group consisting of Rh and Cs; X is C1 , Br, and at least one halogen selected from the group consisting of I: x.

is at least one halogen selected from the group consisting of F, C1, Br and I; and a and X are respectively 0≦a≦4.0 and O<x≦0.2] stimulable phosphor, M'X: Yes; X is C! ; at least one halogen selected from the group consisting of L, Br and I; and
is a numerical value in the range of O<X≦0°2.

Furthermore, M"
The u2゜stimulable phosphor contains additives such as those shown below.
"X2.aM" may be contained in the following proportions per mole of X'2.

bMIX" described in Japanese Patent Application Laid-Open No. 60-166379 by the present applicant (where Ml is Rb and C
X'' is at least one halogen selected from the group consisting of F, C1, Br and I;
is o<b≦10.0); JP-A-60-22148
bKX'”・cMgX”□・described in Publication No. 3
dM"X"' (however, 1M is Sc, Y, La, Gd
and at least one trivalent metal selected from the group consisting of Lu, and X″, X″° and X″ are all F,
At least one halogen selected from the group consisting of C1, Br, and d, and 0≦b≦2゜0.0≦C≦2.0. O≦d≦2.0
and 2×lO−%≦b+c+d); yn(
(However, y is 2X10-4≦y≦2X10-'); bA described in Japanese Patent Application No. 1984-84358 (However, A is at least one selected from the group consisting of SiO□ and P2O5); It is a kind of oxide, and b is 1O-4≦b≦2X10-“; Japanese Patent Application No. 1983
bsio described in the specification of -240452 (however, b is o<b≦3X10-2); bsnX described in the specification of Japanese Patent Application No. 59-240454
"2 (However, X" is at least one kind of halogen selected from the group consisting of F, C1, Br, and B, and b satisfies o<b≦1O-3): Patent application filed in 1983 by the present applicant -bC5x described in specification No. 78033
"・C3nx"°2 (where x" and X"' are each at least one kind of halogen selected from the group consisting of F, Cl, Br and I, and b and C are each o<b≦ 10.0 and 10-6≦C≦2X1
0-2); and a patent application filed by the applicant in 1986-7.
bCsX″・y L described in 8035 specification a
n'' (where X'' is at least one kind of /\logen selected from the group consisting of F, C1, Br and I, and Ln is Sc, Y, Ce, Pr, Nd, Sm.

Gd, Tb, Dy, H0. Er, Tm, Yb and Lu
at least one rare earth element selected from the group consisting of, and b and y each satisfy o<b≦10.0.
and 1O-6≦y≦1.8X l O-').

etc. can be mentioned.

Among the above-mentioned stimulable phosphors, divalent europium-activated alkaline earth metal halide stimulable phosphors and rare earth element-activated rare earth oxyhalide stimulable phosphors exhibit high-intensity stimulated luminescence. However, the stimulable phosphor used in the present invention is not limited to the above-mentioned stimulable phosphor, and it is particularly preferable that the stimulable phosphor exhibits stimulated luminescence when irradiated with radiation and then irradiated with excitation light. Any stimulable phosphor may be used.

Examples of binders for the phosphor layer include proteins such as gelatin,
Polysaccharides such as dextran, or natural polymeric substances such as gum arabic; and polyvinyl butyral, polyvinyl acetate, nitrocellulose, ethylcellulose, vinylidene chloride/vinyl chloride copolymer, polyalkyl (meth)acrylate, vinyl chloride/vinyl acetate Binders typified by synthetic polymeric materials such as copolymers, polyurethanes, cellulose acetate butyrate, polyvinyl alcohol, linear polyesters, etc. may be mentioned. Particularly preferred among such binders are nitrocellulose, linear polyester,
Polyalkyl (meth)acrylates, mixtures of nitrocellulose and &[holJ esters, and mixtures of nitrocellulose and polyalkyl (meth)acrylates.

Note that these binders may be crosslinked with a crosslinking agent.

The phosphor layer can be formed on the light reflecting layer by, for example, a primary method.

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

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

The mixing ratio of the binder and the stimulable phosphor in the coating solution varies depending on the characteristics of the intended radiation image conversion panel, the type of phosphor, etc., but generally the mixing ratio of the binder and the stimulable phosphor is 1. :1 to 1g1o.

(weight ratio), and in particular from 128 to 1
:40 (weight ratio).

The coating liquid also contains a dispersant to improve the dispersibility of the phosphor in the coating liquid, and a dispersant to improve the bonding force between the binder and the phosphor in the phosphor layer after formation. Examples of dispersants used for such purposes include phthalic acid, stearic acid, caproic acid, lipophilic surfactants, etc., which may be mixed with various additives such as plasticizers. can. Examples of plasticizers include phosphate esters such as triphenyl phosphate, tricresyl phosphate, and diphenyl phosphate; phthalate esters such as diethyl phthalate and dimethoxyethyl phthalate; ethyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate, etc. Glycolic acid esters include polyesters of polyethylene glycol and aliphatic 21tim, such as polyesters of triethylene glycol and adipic acid, and polyesters of diethylene glycol and succinic acid.

The coating solution containing the phosphor and binder prepared as described above is then uniformly applied to the surface of the light-reflecting layer to form a coating film of the coating solution.

This coating operation can be carried out using a conventional coating means such as a doctor blade, roll coater, knife coater, etc.

Then, the formed coating film is gradually heated and dried to complete the formation of the phosphor layer on the light reflective layer. The thickness of the phosphor layer varies depending on the characteristics of the intended radiation image conversion panel, the type of phosphor, the mixing ratio of the binder and the phosphor, and is usually 20 gm to 1 mm. However, the thickness of this layer is preferably 50 to 5001 Lm.

Note that the phosphor layer does not necessarily need to be formed by directly applying a coating liquid onto the light reflecting layer as described above; for example,
Separately, a phosphor layer is formed by applying a coating liquid onto a sheet such as a glass plate, metal plate, or plastic sheet and drying, and then this is pressed onto a light reflective layer or by using an adhesive. The light reflecting layer and the phosphor layer may be bonded together.

On the surface of the phosphor layer opposite to the side in contact with the light reflective layer,
A transparent protective film may be provided for the purpose of physically and chemically protecting the phosphor layer.

The transparent protective film may be made of a transparent material such as a cellulose derivative such as cellulose acetate or nitrocellulose; or a synthetic polymer material such as polymethyl methacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyvinyl acetate, or vinyl chloride/vinyl acetate copolymer. The phosphor layer can be formed by coating the surface of the phosphor layer with a solution prepared by dissolving a polymeric substance in a suitable solvent. Alternatively, it can also be formed by a method such as adhering a transparent thin film separately formed from polyethylene terephthalate, polyethylene, polyvinylidene chloride, polyamide, etc. to the surface of the phosphor layer using a suitable adhesive. The thickness of the transparent protective film formed in this way is
Preferably, it is about 0.9 to 20 tons.

In addition, JP-A-55-163500, JP-A-57-
As described in Japanese Patent No. 96300 and the like, the radiation image conversion panel of the present invention may be colored with a young coloring agent, and the sharpness of the image obtained can be improved by coloring. Furthermore, as described in Japanese Patent Application Laid-Open No. 55-146447, the radiation of the present invention! The a-image conversion panel may have white powder dispersed in its phosphor layer for the same purpose.

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

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

[Example 1] Styrene-acrylic hollow polymer particles (VONGQA
T PP-2QQQS, Dainippon Ink Chemical Co., Ltd.) and acrylic ester (Arontac A-2422H)
.

(manufactured by Toagosei ■) to prepare a coating IIi solution in which the hollow polymer particles were uniformly dispersed and the mixing ratio of the binder and the hollow polymer particles was 1=5 (weight ratio).

This coating solution was uniformly applied using a doctor blade onto a polyethylene terephthalate film (support, thickness: 250 JLm) placed horizontally on a glass plate. After coating, the support on which the coating 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. In this way, a light reflecting layer with a layer thickness of 50 gm was provided on the support.

Next, 90 parts by weight of vinyl acetate (manufactured by Kishida Kagaku ■) and 710 parts by weight of nitrocellulose were added to a mixed solvent of ethanol and methyl ethyl ketone (mixing ratio 7:3), and roughly stimulable divalent europium-activated filtrate was added. After adding barium bromide phosphor (BaFBr:Eu'') particles, the phosphor particles are uniformly dispersed by stirring and mixing thoroughly using a propeller mixer, and the mixing ratio of the binder and the phosphor is 1. :20 (weight ratio) and a viscosity of 25 to 30 PS (25°C) was prepared.

This coating liquid was applied onto the light reflecting layer by the same operation as above, and then dried to form a phosphor layer with a layer thickness of 350 pm.

Then, a transparent protective film is formed by placing and adhering a polyethylene terephthalate film (thickness = 121 Lm, coated with a polyester adhesive) on top of this phosphor layer with the adhesive layer side facing down. did.

In this way, a radiation image conversion panel was produced which was composed of a support, a light reflecting layer, a phosphor layer and a transparent protective film.

[Comparative Example 1] Example 1 except that titanium dioxide was used instead of the styrene/acrylic hollow polymer particles.
A light-reflecting layer was formed on the support by performing a treatment similar to the method described above.

Next, by performing the same treatment as in Example 1 using the support provided with this light-reflecting layer, a radiation image composed of the support, the light-reflecting layer, the phosphor layer, and the transparent protective film is obtained. A conversion panel was manufactured.

Next, the spectral reflectance of each of the light reflecting layers of Example 1 and Comparative Example 1 was measured using a spectrophotometer (Hitachi Self-Recording Spectrophotometer Model 330). The results are summarized in FIG. 1 and Table 1.

Figure 1 is.

1: Reflection spectrum of a light-reflecting layer made of hollow polymer particles 2 Represents the reflection spectrum of a light-reflecting layer made of titanium dioxide.

Table 1 Light reflection Kj 350 nm light 550 nm light Hollow polymer particles 95 95 Titanium dioxide 9 88 From the results summarized in Figure 1 and Table 1, it is clear that the radiation image conversion panel of the present invention is composed of hollow polymer particles. The light-reflecting layer (Example 1) has a reflection spectrum that extends to the shorter wavelength side than the light-reflecting layer made of titanium dioxide (Comparative Example 1).
It was clear that the material had excellent reflection properties in the near ultraviolet to r+f viewing region of 450 nm.

In addition, each of the obtained radiation image conversion panels was evaluated by the sensitivity test, image sharpness test, and image graininess test described below.

(1) Sensitivity test After irradiating the radiation image conversion panel with X-rays with a tube voltage of 80 KVp,
m) and the sensitivity was measured.

(2) Image sharpness test CT X-rays with a tube voltage of 80 KVP are applied to the radiation image conversion panel.
After irradiating through the F chart, the phosphor particles are excited by scanning with a He-Ne laser beam, and the stimulated luminescence light emitted from the phosphor layer is sent to a receiver (photomultiplier tube with spectral sensitivity S-5). The received light was converted into an electrical signal, and this was reproduced as an image by an image reproducing device to obtain an image of a CTF chart on a display device. The contrast transfer function (CTF) was measured from the obtained image and evaluated as a value at a spatial frequency of 2 cycles/mm.

(2) Image graininess test The radiation image conversion panel had a tube voltage of 80 KVP and a wire bond of 100 KVP.
mRc7) After irradiating X-rays, the phosphor particles are excited by scanning with a He-Ne laser beam, and the stimulated luminescence light emitted from the phosphor layer is collected using a photoreceiver (a photomultiplier tube with a spectral sensitivity of S-5). ) receives the light and converts it into an electrical signal, which is recorded on ordinary photographic film by a film scanner, and the resulting image has a photographic density D=1.2. Spatial frequency 0.4~
The RMS value at 5 lines/mm was determined. This RMS value was used as a measure of graininess.

The results are summarized in Table 2. Note that the sensitivity and sharpness are expressed as relative values when the value of Comparative Example 1 is taken as 100.

Margin Table 2 Sensitivity Sharpness Graininess Example 1 135 9B 2.51X10
-2 Comparative Example 1 100 100 2. fi9X
As is clear from the results shown in Table 2 of 1O-2, the radiation image storage panel of the present invention (Example 1) having a light reflection layer made of hollow polymer particles has a light reflection layer made of titanium dioxide. The sensitivity was significantly improved compared to the conventionally known radiation image conversion panel (Comparative Example 1). Furthermore, the panel of the present invention provided an image that had almost the same sharpness as a known panel and had significantly higher graininess.

[Brief Description of the Drawings] Figure 1 shows the reflection spectrum (1) of a light reflecting layer made of hollow polymer particles constituting the radiation image storage panel of the present invention.
, and a graph showing the reflection spectrum (2) of a light-reflecting layer made of conventionally known titanium dioxide.

Claims (1)

[Scope of Claims] 1. A support, a light-reflecting layer made of a binder containing and supporting a light-reflecting substance in a dispersed state, and a phosphor layer made of a binder containing and supporting a stimulable phosphor in a dispersed state. 1. A radiation image conversion panel having the following in this order, wherein the light reflection layer contains polymer particles having a hollow structure as a light reflection substance. 2. The outer diameter of the hollow structured polymer particles is in the range of 0.2 to 1 μm, and the small pore diameter is in the range of 0.05 to 1 μm.
The radiation image conversion panel according to claim 1, characterized in that the thickness is in the range of 0.7 μm. 3. The hollow structured polymer particles are styrenic and/or
or an acrylic polymer, the radiation image conversion panel according to claim 1. 4. The radiation image conversion panel according to claim 1, wherein the weight mixing ratio of the binder and the hollow polymer particles in the light reflecting layer is in the range of 1:1 to 1:50. . 5. Claim 1, wherein the stimulable phosphor is a phosphor that exhibits stimulated luminescence in a wavelength range of 300 to 500 nm when excited by excitation light in a wavelength range of 400 to 900 nm. radiographic image conversion panel. 6. The radiation image conversion panel according to claim 5, wherein the stimulable phosphor is a divalent europium activated alkaline earth metal halide phosphor. 7. The radiation image conversion panel according to claim 5, wherein the stimulable phosphor is a rare earth element-activated rare earth oxyhalide phosphor.