JP2003202399A - Radiation image conversion panel and method for manufacturing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation image conversion panel which has a high relative luminance and exhibits good resolution and a method for manufacturing the panel. <P>SOLUTION: The radiation image conversion panel is characterized in that it has on a support a phosphor layer which includes the particles of spherical phosphors which contain at least one selected among such rare-earth elements as Nd, Gd, Tb, Dy, Ho, Er, Tm and Yb, whose crystal sizes are 10 to 100 nm and where a larger quantity of an activator exists on the right side. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a radiation image conversion panel and a method for manufacturing the same.

[0002]

2. Description of the Related Art A phosphor mainly containing a rare earth metal compound is a main material for constructing a radiation image conversion panel.
Conventionally, Gd ₂ O ₂ S: Tb, La ₂ O ₂ S:
Although Tb and the like have been mainly used, the production method thereof was prepared by repeating the steps of mixing a rare earth oxide and a sulfur compound, adding a flux and firing and crushing.

For this reason, it is difficult for the phosphors produced by the above-mentioned manufacturing method to have a uniform particle shape, and the morphology of the particles tends to collapse due to cracks generated during crushing or cooling of crystals. When a radiation image conversion panel is produced, the particle size distribution becomes wide, and the phosphor existing state in the panel becomes irregular. As a result, image blurring and the like are likely to occur.

That is, when an image is formed by X-ray photography, incident X-rays are scattered in the phosphor layer due to its particle size distribution and particle structure, which causes blurring of the image and other factors that deteriorate the resolution. The influence of scattering in the phosphor layer is particularly remarkable at the X-ray tube voltage, and the sharpness characteristic is 6
The current situation is that satisfactory image information cannot be obtained, which causes a reduction in resolution in a high frequency region of (lp / mm) or more.

Further, since the shape of the phosphor particles is non-uniform, it is difficult to make the phosphor layer highly filled, and the image quality performance such as brightness is not sufficiently satisfied, and there is a demand for urgent improvement.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a radiation image conversion panel exhibiting high relative luminance and good resolution (also referred to as little image blur). It is to provide the manufacturing method. In particular, it is an object of the present invention to provide a radiation image conversion panel having excellent sensitivity and sharpness used in medical X-ray imaging in which X-rays having a low tube voltage are used, and a method for manufacturing the same.

[0007]

The above objects of the present invention have been achieved by the following constitutions 1 to 5.

1. Rd, Nd, G on the support
It contains at least one selected from d, Tb, Dy, Ho, Er, Tm and Yb, and has a crystallite size of 10 to 10.
A radiation image conversion panel, which has a phosphor layer containing spherical phosphor particles having a large amount of an activator on the surface side, which is 0 nm.

2. 2. The radiation image conversion panel according to 1 above, wherein the amount of the rare earth element Gd present is large on the surface side of the spherical phosphor particles.

3. The rare earth element Y is present in a small amount on the surface side of the spherical phosphor particles.
The radiation image conversion panel described in 1.

4. Rd, Nd, G on the support
It contains at least one selected from d, Tb, Dy, Ho, Er, Tm and Yb, and has a crystallite size of 10 to 10.
A method for producing a radiation image conversion panel, which comprises coating a phosphor layer containing spherical phosphor particles having a large amount of activator on the surface side of 0 nm.

5. In order to manufacture a radiation image conversion panel by coating and drying a phosphor layer coating liquid in which spherical phosphor particles are dispersed and contained in a binder and a solvent on a support, spherical particles contained in the phosphor layer coating liquid The phosphor particles contain at least one selected from the rare earth elements Nd, Gd, Tb, Dy, Ho, Er, Tm, and Yb, and have a crystallite size of 1
A method for producing a radiation image conversion panel, which has a size of 0 to 100 nm and in which a large amount of activator is present on the surface side.

The present invention will be described in detail below. The radiation image conversion panel of the present invention has a support and a phosphor layer or a self-supporting phosphor layer provided on the surface thereof, and the phosphor layer usually contains a phosphor and a binder for dispersing and supporting the phosphor. Alternatively, an embodiment in which only the aggregate of the phosphors formed by the vapor deposition method or the sintering method is used can be used.

Further, a polymer substance may be impregnated into the gap between the aggregates of the phosphor, and a polymer film or an inorganic substance is usually provided on the surface opposite to the phosphor layer side with the support interposed. A protective layer film made of the vapor-deposited film may be provided.

As a result of proceeding with analysis of the image quality deterioration factor in image formation by X-ray irradiation through the radiation image conversion panel, the present inventors have found that one of the factors of sharpness deterioration is the phosphor layer of the radiation image conversion panel. The irregular shape of the phosphor particles contained in the layer and the uneven distribution of the phosphor particles in the layer induce irregular scattering of incident X-rays, resulting in a decrease in resolution in the high frequency region. It was found that the scattering of the X-rays in the phosphor layer was remarkable when the image was taken at a low tube voltage where the X-ray energy intensity was low. As a result of earnest studies based on the analyzed phenomenon, the present inventors have found that the crystallite size is 10 to 1
It is 00 nm and it is found that it can be achieved by using spherical phosphor particles in which the amount of the activator is large on the surface side, and in order to further exert the effect aimed at by the present invention, a specific rare earth element ( It was found that it is effective to use spherical phosphor particles having a large amount of Gd) present on the surface, or spherical phosphor particles having a small amount of a specific rare earth element (Y) present on the surface, and upon reaching the present invention Is.

Although it is not clear that the effects of the present invention can be obtained by using the spherical phosphor particles described above, the present inventors have found that the particle distribution and particle structure of the spherical phosphor particles according to the present invention. -Based X-ray scattering in a radiation image conversion panel, especially X-ray intra-film scattering on the high frequency side of 6 (lp / mm) or more (specifically, resolution at 10 (lp / mm)) It is believed that this is because it is reduced compared to conventionally known phosphor particles. << Phosphor Particles >> The phosphor particles according to the present invention will be described.

The phosphor particles according to claim 1 are rare earth elements Nd, Gd, Tb, Dy, Ho, Er, Tm and Y.
It is characterized by containing at least one selected from b and having a crystallite size of 10 to 100 nm.

Here, the crystallite size was calculated by the "Wilson method" in which 10 to 15 measurable peaks of diffraction peaks obtained by X-ray diffraction were selected and measured. As a method for calculating the crystallite size, the method described in Kyoritsu Shuppan Co., Ltd .: Instrument analysis practical series, X-ray analysis method can be used.

Further, the phosphor particles according to the first aspect are characterized in that the activator is present in a large amount on the surface side.

Regarding the existing amount of the activator, specifically, the phosphor particles are fixed with a resin and cut with a microtome.
To confirm the position, the center (center of gravity) in the cut cross section is determined, and the inside of the line connecting the center and the middle point of the outermost end is the inside, and the outside is the outside. For evaluation, the cross section of the phosphor is made as thin as possible. The obtained thin piece of the phosphor is subjected to elemental analysis using TEM,
The activators on the inside and outside (front side) are measured.

As a result of this measurement, the effect of the present invention can be achieved when the existing amount of the activator is on the surface side> inside.

The activator referred to here is one existing in the host crystal and serving as an excitation source for emitting light, and (Y, G
Eu is an activator for d, Eu) ₂ O _{3 and} Tb is an activator for (Y, Gd, Tb) ₂ O ₃ .

Due to the large amount of activator present on the surface side, in a Gd-based material having a large absorption of X-rays, the large amount of activator on the surface side allows efficient light emission. In particular, in a system in which a light receiving element (film or the like) is arranged in the same direction as the X-ray incident side, the effect of suppressing light scattering is significantly great as the amount of emitted light increases.

In the present invention, it is preferable that the amount of the rare earth element Gd in the phosphor particles is large on the surface side of the phosphor particles. This makes it possible to efficiently increase the absorption of X-rays and form a large number of emission centers.

Alternatively, the amount of the rare earth element Y present is preferably small on the surface side of the phosphor particles. This makes it possible to suppress light scattering on the surface of the phosphor particles.

Further, from the viewpoint of obtaining an image with high sharpness with less image blur, the following configurations (1) to (5) are preferably adopted. (1) The spherical phosphor particles have a composition represented by the following general formula (1).

In the general formula (1) (Gd, M) ₂ O ₃ , M is Y, Nd, Tb, Dy, Ho, Er, Tm,
It represents at least one atom selected from the atomic group consisting of Yb, Eu, La, Lu, Sm, and Ce, and the atom preferably used among them is Y, Eu, Tb, or the like.

From the viewpoint of further improving the emission characteristics of the phosphor particles, the content of Y and Eu in the phosphor particles is preferably 2 to 20% by mass, more preferably 5 to 20% by mass.
It is 10% by mass. Further, the content of Tb in the phosphor particles is preferably 0.01 to 4% by mass. (2) Improving the X-ray absorption amount of the radiation image conversion panel (within the maximum exposure range of the exposure dose of the subject), and
From the viewpoint of improving the brightness characteristics, the spherical phosphor particles have a Gd of 7
It is preferable to contain 1 to 98% by mass. (3) The particle size of the spherical phosphor particles is preferably 0.1 to 5 μm, more preferably 0.3 to 2 μm.

Here, for the particle size measurement of the phosphor particles, the phosphor is dispersed in water using a suitable surfactant, and the particle size is measured using a light scattering method particle measuring device (eg, Horiba LA-910). Can be measured and obtained. (4) The crystallite size of the spherical phosphor particles is 300 to 75 from the viewpoint of improving the light emission characteristics of the spherical phosphor particles and suppressing the increase of the crystallite size and the disorder of the particle shape.
It is preferably 0 nm. (5) In order to improve the relative brightness and obtain spherical phosphor particles having a preferable crystal form and crystal size, the firing temperature is preferably set to 500 ° C. or higher, more preferably 700 ° C. or higher, and particularly preferably Preferably firing temperature 900
C to 1300C. << Crystal Form of Phosphor Particles >> The crystal form of the phosphor particles according to the present invention can be various crystal forms such as a flat crystal, a cubic crystal, a tetradecahedral crystal and a sphere crystal. In order to increase the filling rate, spherical crystals are particularly preferably used. << Spherical Phosphor Particles >> The phosphor particles may be a single crystal or an aggregate of a plurality of fine particles, but as the phosphor particles according to the present invention, spherical crystals or spherical particles are preferably used. However, the spherical particles do not necessarily have to be aggregates of spherical crystals, and include cases where aggregates of particles having other crystal forms eventually form spherical particles.

The spherical shape of the spherical phosphor particles means that the spherical crystal or the long diameter of the spherical particles is obtained from a photograph of the phosphor particles photographed by using a scanning electron microscope (50 to 100 particles are observed as a photograph of the particles). (A) and minor axis (b) (each is an average value), and the ratio of major axis and minor axis: (a) / (b)
Is in the range of 0.98 to 1.00.

The spherical phosphor particles according to the present invention may be single crystals, single crystal aggregates, or crystal aggregates of other forms, but the final particle form is spherical. It is necessary.

In the present invention, in order to clarify a clear boundary between a sphere and another polyhedron, for example, in the case of a polyhedral crystal, the ratio of the longest diameter to the shortest diameter of the polyhedron is in the above range. Those that fall within the scope of the present invention are also defined as falling within the spherical category in the present invention.

Further, polyhedrons having 14 or more sides and falling within the above range are defined as substantially spherical.

In order to increase the packing efficiency of the crystals in the phosphor particles, spherical crystals are particularly preferably used because the packing efficiency increases in the order of flat plate <cube <14th face <sphere. << Production Method of Spherical Phosphor Particles >> Next, a production method of the spherical phosphor particles according to the present invention will be specifically described.

(Formulation 1): Urea is added to an aqueous solution containing a salt of the above-mentioned rare earth element (hydrochloride, sulfate, nitrate etc. as the salt of the rare earth element) to precipitate a basic carbonate, and the obtained precipitate is obtained. Is subjected to solid-liquid separation and baked at 500 ° C. or higher to obtain phosphor particles on spherical fine particles.

(Formulation 2): The above-mentioned aqueous solution containing a rare earth element is heated at 80 ° C. or higher for 0.5 to 5 hours, hydrogen peroxide and urea are added, and the mixture is further heated to give basic carbonate of the rare earth element. Spherical particles of salt are precipitated, and then the precipitated basic carbonate of rare earth element is subjected to solid-liquid separation to obtain spherical particles of basic carbonate of rare earth element.

The spherical particles of the rare earth element oxide can be obtained by further baking the spherical particles of the basic carbonate in air or in an oxidizing atmosphere.

The reaction conditions for precipitation of the basic carbonate of the rare earth element from the aqueous solution of the rare earth element used in the above formulations 1 and 2 will be described in more detail.

The salt of the water-soluble rare earth element used in the present invention is preferably a nitrate. The amount of urea used in Formulation 1 and Formula 2 is preferably about 3 to 5 times the concentration of the rare earth element, and when hydrogen peroxide is used, the amount of hydrogen peroxide added is the concentration of the rare earth ion. To 1/1
Addition is preferably from 30 to 30/100.

By firing the obtained basic carbonate of a rare earth element in air or in an oxidizing atmosphere, spherical rare earth element oxide particles can be obtained while maintaining the shape of the basic carbonate. However, the firing temperature is preferably 500 ° C. or higher.

Further, a basic carbonate is prepared by using a urea compound in an aqueous solution containing the rare earth element. Here, the urea compound is urea or a salt of urea (eg, nitrate, citrate, etc.). ), N, N′-diacetylurea, N, N ′
-Dibenzoylurea, N, N-dibenzoylurea, benzenesulfonylurea, p-toluenesulfonylurea, trimethylurea, tetraethylurea, tetramethylurea,
Triphenylurea, tetraphenylurea, N-benzoylurea, methylisourea, ethylisourea and the like are preferably used, but urea is particularly preferably used.

Regarding the formation of spherical phosphor particles, in addition to the above-mentioned basic carbonate using urea, oxalate, organic phosphate, malonate, glycolate, sebacate, cacodylate and various other salts are used. Benzenesulfonic acid derivative salts, aminopolyacetates (EDTA, DCTA, HEDT
A, DE, ME, NTA, IMDA) Acetylacetonate, an alkoxide, a cyclooctatetraene complex, a cyclopentadiene complex, or the like deposited may be used.

When the spherical phosphor according to the present invention is a matrix-excited type phosphor, it is preferable that the spherical phosphor is sensitive to the completeness of the host crystal and enhances the crystallinity. The rate, crystal structure, and product decomposition are important.

Further, from the viewpoint of improving the brightness characteristics of the phosphor, it is important to select the distribution of the luminescence centers and the valence of the luminescent ions. For example, rare earth elements used during the firing of the spherical phosphor particles according to the present invention. Eu as an activator among the elements
^{Firing in} an oxidizing atmosphere when introducing easily-reduced ions such as ³⁺ , and in a reducing atmosphere when introducing easily-oxidizable ions such as Eu ²⁺ , Tb ³⁺ , Ce ³⁺ , Pr ³⁺ Preferably. << Phosphor Layer >> The phosphor layer according to the present invention will be described.

In the present invention, the filling rate of the phosphor in the phosphor layer is preferably 60% or more, more preferably 65% or more. In the production of the phosphor layer, the upper limit of the filling rate of the phosphor layer is preferably 100% or less, more preferably 85% or less. Here, the filling rate measurement of the phosphor in the phosphor layer, the protective layer of the radiation intensifying screen is removed, the entire phosphor layer is peeled or eluted using an organic solvent or the like, and after filtration and drying, The mass of the phosphor obtained by removing the resin on the surface by baking for 1 hour at 600 ° C using an electric furnace is M
(G), where P (cm) is the thickness of the phosphor layer before elution, Q (cm ² ) is the area of the phosphor sheet used for elution, and R (g / cm ³ ) is the specific gravity of the phosphor. Filling rate = [M / (P × Q × R)] × 100 (%).

Examples of the binder used in the phosphor layer are proteins such as gelatin, polysaccharides such as dextran, or natural polymer substances such as gum arabic; and polyvinyl butyral, polyvinyl acetate, nitrocellulose, Ethyl cellulose, vinylidene chloride / vinyl chloride copolymer, polyalkyl (meth) acrylate,
Examples thereof include binders represented by synthetic polymer substances such as vinyl chloride / vinyl acetate copolymer, polyurethane, cellulose acetate butyrate, polyvinyl alcohol, and linear polyester.

Preferred among such binders are:
Nitrocellulose, linear polyesters, polyalkyl (meth) acrylates, mixtures of nitrocellulose and linear polyesters, mixtures of nitrocellulose and polyalkyl (meth) acrylates and mixtures of polyurethane and polyvinyl butyral. In addition, these binders may be crosslinked with a crosslinking agent.

Further, a polyester resin or a polyurethane resin having a sulfonic acid group is preferably used as the binder capable of enhancing the dispersibility of the phosphor and increasing the filling rate.

The above-mentioned binder is preferably used in the range of 0.01 to 1 part by mass with respect to 1 part by mass of the phosphor, and further, in view of ease of coating, 0.03 to 0.
It is preferably used in the range of 2 parts by mass.

The mixing ratio of the binder and the phosphor in the coating liquid for preparing the phosphor layer (however, when all the binder is an epoxy group-containing compound, it is equal to the ratio of the compound and the phosphor), The characteristics of the desired radiation image conversion panel, the type of phosphor, the amount of epoxy group-containing compound added, etc., but generally as an example of a solvent for preparing a coating solution,
Lower alcohols such as methanol, enothal, 1-propanol, 2-propanol and n-butanol; chlorine atom-containing hydrocarbons such as methylene chloride and ethylene chloride; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexane; methyl acetate, acetic acid Examples include esters of lower fatty acids such as ethyl and butyl acetate with lower alcohols; ethers such as dioxane, ethylene glycol ethyl ether, ethylene glycol monomethyl ether; toluene; aromatic compounds such as triol and xylol, and mixtures thereof. it can. It is preferable that the amount of the solvent for adjusting the coating liquid is small in order to increase the specific gravity of the phosphor layer.

Specifically, the amount of solvent in the coating liquid is 25% by mass or less, more preferably 20% by mass or less. Further, in order to form a dense film by slowly drying after coating, it is preferable to use a high boiling point solvent such as cyclohexane as a solvent for the coating liquid, and when the solvent is a mixed solvent,
The proportion of the high boiling point solvent is 40% by mass or more, preferably 50% by mass or more.

In the coating liquid, a dispersant for improving the dispersibility of the phosphor in the coating liquid and a binding force between the binder and the phosphor in the formed phosphor layer are improved. Various additives such as plasticizers may be mixed. Examples of dispersants used for such purpose include phthalic acid, stearic acid, caproic acid, lipophilic surfactants and the like. Examples of the plasticizer include phosphoric acid esters such as triphenyl phosphate, tricresyl phosphate, diphenyl phosphate; phthalic acid esters such as diethyl phthalate and dimethoxyethyl phthalate; ethyl phthalyl ethyl 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.

In order to improve the dispersibility of the phosphor particles in the phosphor layer coating liquid, stearic acid, phthalic acid,
A dispersant such as caproic acid or a lipophilic surfactant may be mixed. If necessary, a plasticizer for the binder may be added. Examples of the plasticizer include phthalic acid esters such as diethyl phthalate and dibutyl phthalate, diisodecyl succinate, aliphatic dibasic acid esters such as dioctyl adipate, ethyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate. And glycolic acid esters such as.

The coating solution prepared as described above is then uniformly applied to the surface of the undercoat layer on the support to form a coating film of the coating solution. This coating operation can be performed by using an ordinary coating means such as a doctor blade, a roll coater or a knife coater. Next, the formed coating film is dried by gradually heating to complete the formation of the phosphor layer on the undercoat layer.

The layer 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, etc., but is usually 10 μm to 1 mm.
(Layer thickness after drying). In particular, when it is used for mammography, it is a coating film having an increased filling rate and its layer thickness is 200 μm or less, more preferably 100 μm or less.

The coating solution for the phosphor layer is prepared by a ball mill,
It is carried out using a dispersing device such as a sand mill, an attritor, a triple roll mill, a high speed impeller disperser, a Kady mill, and an ultrasonic disperser. The phosphor layer is formed by applying the prepared coating solution on a support using a coating solution such as a doctor blade, a roll coater, or a knife coater and drying. The phosphor layer may be adhered to the support after the coating liquid is applied onto the protective layer and dried.

As the support used in the radiation image conversion panel of the present invention, various polymer materials, glass, metal and the like are used. In particular, those that can be processed into a flexible sheet or web from the viewpoint of handling as an information recording material are preferable, and in this respect, cellulose acetate film, polyester film, polyethylene terephthalate film, polyamide film, polyimide film, triacetate film. , Plastic films such as polycarbonate film, aluminum, iron,
A metal sheet such as copper or chromium or a metal sheet having a coating layer of the metal oxide is preferable.

The layer thickness of these supports varies depending on the material of the support used, etc., but is generally 3 to 1000 μm.
From the viewpoint of handling, 80 to 5 is more preferable.
It is 00 μm. The surface of these supports may be a smooth surface, or may be a matte surface for the purpose of improving the adhesiveness with the phosphor layer.

Further, in these supports, an undercoat layer may be provided on the surface on which the phosphor layer is provided for the purpose of improving the adhesiveness with the phosphor layer.

From the viewpoint of increasing the reflectivity of the support and improving the brightness of the radiation image conversion panel, polyethylene terephthalate containing bubbles is preferably used for the support in the present invention.

Here, the polyethylene terephthalate containing the above-mentioned bubbles is made to contain the bubbles in the polyethylene terephthalate by the method described in JP-A-3-76727 and JP-A-6-226894 to reflect the stimulated fluorescence. It is possible to manufacture a support having a high radiation efficiency and improved brightness of the radiation image conversion panel. Commercially available products include polyethylene terephthalate containing bubbles such as E60L manufactured by Toray Industries, Inc.

The thickness of the polyethylene terephthalate support containing the bubbles is generally 80 to 1000 μm.
m, and preferably 50 to 50 from the viewpoint of handling.
It is 0 μm.

The surface of these supports may be a smooth surface, or may be a matte surface for the purpose of improving the adhesiveness with the reflection layer, the light absorption layer and the phosphor layer. << Method for Manufacturing Radiation Image Conversion Panel >> A method for manufacturing the radiation image conversion panel according to the present invention will be described.

The following two main methods of manufacturing the radiation image conversion panel are considered. As a first manufacturing method, a phosphor coating liquid (hereinafter referred to as phosphor coating material) including a binder and a phosphor is applied on a support to form a phosphor layer.

As a second manufacturing method, a phosphor coating composed of a binder and a phosphor is applied on a temporary support to form a phosphor sheet. Place the phosphor sheet on a support,
It is manufactured in the step of adhering to the support at a softening temperature of the binder or at a temperature higher than the melting point.

As a method for forming the phosphor layer on the support,
The above-mentioned two types are mainly conceivable, but any method may be used as long as it is a method for uniformly forming a phosphor layer on a support, and spraying or the like may be used.

The phosphor layer of the first manufacturing method can be manufactured by applying a phosphor coating material in which a phosphor is uniformly dispersed in a binder solution onto a support and drying it.

Further, the sheet to be the phosphor layer of the second manufacturing method is coated with the phosphor coating on the temporary support for forming the phosphor sheet or on the protective film provided on the temporary support and dried. rear,
It can be manufactured by peeling from the temporary support. The protective film itself can be used as a temporary support in the final product as it is.

In the second manufacturing method, a phosphor coating is applied on a temporary support or a protective film provided on the temporary support, dried, and then peeled from the temporary support to form a phosphor layer. And Therefore, it is preferable that the surface of the temporary support is coated with a release agent in advance so that the formed phosphor sheet can be easily separated from the temporary support.

In order to strengthen the bond between the support and the phosphor layer, a high molecular substance such as polyester or gelatin is applied to the surface of the support to provide an undercoat layer for imparting adhesiveness, sensitivity, image quality (sharpness, granularity). In order to improve the property), a light reflecting layer made of a light reflecting substance such as titanium dioxide or a light absorbing layer made of a light absorbing substance such as carbon black may be provided. Those configurations can be arbitrarily selected according to the purpose, application, etc.

Further, the phosphor layer of the present invention may be compressed.
By compressing the phosphor layer, the packing density of the phosphor can be further improved, and the sharpness and graininess can be further improved. Examples of the compression method include a press machine and a calendar roll.

In the case of the first manufacturing method, the phosphor layer and the support are compressed as they are. In the case of the second production method, the phosphor sheet is placed on a support, and the sheet is adhered to the support while being compressed at the softening temperature or the melting point or higher of the binder.

In this way, the sheet can be spread thinly by using the method of pressing the phosphor sheet on the support without fixing it in advance.

Next, the formed coating film is gradually heated and dried to form a phosphor layer on the undercoat layer (also referred to as an undercoat layer).

The film thickness of the stimulable phosphor layer of the radiation image conversion panel of the present invention is the desired characteristics of the radiation image conversion panel, the type of stimulable phosphor, the mixture of the binder and the stimulable phosphor. Although it depends on the ratio and the like, it is preferably selected from the range of 10 to 1000 μm, more preferably 10 to 500 μm.

A phosphor sheet having a phosphor layer coated on a support is cut into a predetermined size. Although any general method can be used for cutting, a cosmetic cutting machine, a punching machine or the like is preferable in terms of workability and accuracy.

[0077]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited to these.

Example 1 <Preparation of Phosphor Particles 1> The total concentration of yttrium ions, gadolinium ions, and europium ions was 0.05 mol / liter, and the ion content ratio (molar ratio was Y / Gd / Eu) in an aqueous solution. ) Was heated to 95 ° C. Hydrogen peroxide was added to this aqueous solution so that the concentration of hydrogen peroxide was 0.01 mol / liter, and urea was added so that the concentration was 0.6 mol / liter, and the mixture was heated at 95 ° C. for 1 hour to produce a rare earth element. As elements, a basic rare earth carbonate compound containing 20% by mass of Y, 71% by mass of Gd, and 9% by mass of Eu was prepared.

The precipitated rare earth compound was separated by a membrane filter and calcined at 700 ° C. for 2 hours to give a particle size of 1
Spherical phosphor particles 1 of μm were obtained. Table 1 shows the content ratio of each Y / Gd / Eu on the surface / inside of the obtained phosphor particles 1. << Preparation of Phosphor Particles 2-12 >> In the preparation of the above-mentioned phosphor particles 1, the content ratio of yttrium ions / gadolinium ions / europium ions in the phosphor particles on the particle surface / inside is as shown in Table 1. Phosphor particles 2-1 are changed in the same manner except that the shape of the phosphor particles is adjusted.
2 was produced.

Regarding the shapes of the phosphor particles 1 to 12, the average major axis (a) and the average minor side diameter of the spherical particles of the phosphor particles obtained by observation with a scanning electron microscope (observation of 20 to 50 particles). The ratio (a) / (b) of (b) is calculated, and the ratio (a) /
Those having (b) in the range of 0.98 to 1.00 were determined to be spherical. It was found that the obtained phosphor particles 1 to 12 were all spherical. << Preparation of Radiation Image Conversion Panel Samples 1 to 12 >> Each of the particles prepared above is 98.5% by mass, polyester resin Byron 630 (manufactured by Toyobo) is 1.5% by mass, and organic solvent cyclohexanone is 25.0% by mass. To obtain a pigment slurry. The prepared pigment slurry is coated on a support (PET (188X-30 manufactured by Toray)) with a knife coater having a gap of 200 μm, the coating film is dried at 100 ° C. for 30 minutes, and then a 2 μm PET film is coated. After laminating it on the top, it is cut into a predetermined size to prepare a plate, and radiation image conversion panel samples 1 to 12 are prepared.
Were produced respectively. (Evaluation) The obtained radiation image conversion panel samples 1 to 12 were evaluated as follows. The results obtained are shown in Table 1. << Evaluation of relative brightness >> A tube voltage of 80 is applied to the radiation image conversion panel.
Irradiate with kVp and 50 mA X-ray. The emitted light emitted from the radiation image conversion panel during irradiation is received by using a photomultiplier tube (photomultiplier tube R1305 manufactured by Hamamatsu Photonics), and the intensity of the emitted light is measured for the radiation image conversion panel sample 4.
The relative luminance was set to 00. << Resolution Evaluation at 10 (lp / mm) >> For the resolution evaluation, the signal difference at the lead slit portion at the spatial frequency of 10 (lp / mm) of the X-ray MTF chart (No. 1 manufactured by Aurora) is 1
It was evaluated as the resolution at 0 (lp / mm). here,
The signal difference of the radiation image conversion panel sample 1 was expressed as 100, and the other radiation image conversion panel samples were evaluated as relative values.

[0081]

[Table 1]

As is clear from Table 1, the sample of the present invention, in which the amount of Eu, which is the activator, is present on the surface side of the phosphor particles is larger than that of the comparative sample, is superior in relative luminance and resolution. . Further, it can be seen that particularly when the amount of Gd present is large on the surface side of the phosphor particles, the relative brightness is excellent and the light emission is performed efficiently. On the other hand, it can be seen that when the amount of Y present is small on the surface side of the phosphor particles, the resolution is excellent and the X-ray scattering is suppressed.

[0083]

EFFECTS OF THE INVENTION According to the present invention, it is possible to provide a radiation image conversion panel having a high relative luminance and a good resolution and a method of manufacturing the same, which is a remarkably excellent effect.

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Claims (5)

[Claims] 1. A rare earth element such as Nd, Gd, or
It contains at least one selected from Tb, Dy, Ho, Er, Tm and Yb, and has a crystallite size of 10 to 100 n.
A radiation image conversion panel having a phosphor layer containing spherical phosphor particles having a large number of activators on the surface side. 2. The radiation image conversion panel according to claim 1, wherein the abundance of the rare earth element Gd is large on the surface side of the spherical phosphor particles. 3. The rare earth element Y is present in a small amount on the surface side of the spherical phosphor particles.
The radiation image conversion panel described in 1. 4. A rare earth element such as Nd, Gd, or
It contains at least one selected from Tb, Dy, Ho, Er, Tm and Yb, and has a crystallite size of 10 to 100 n.
A method of manufacturing a radiation image conversion panel, characterized in that a phosphor layer containing spherical phosphor particles having a large amount of activator is present on the surface side. 5. A phosphor layer coating liquid for producing a radiation image conversion panel by coating and drying a phosphor layer coating liquid in which spherical phosphor particles are dispersed and contained in a binder and a solvent on a support. The spherical phosphor particles contained in are the rare earth element N
It contains at least one selected from d, Gd, Tb, Dy, Ho, Er, Tm and Yb, and has a crystallite size of 10
-100 nm, and the activator is present in a large amount on the surface side.